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      1 /* libs/opengles/primitives.cpp
      2 **
      3 ** Copyright 2006, The Android Open Source Project
      4 **
      5 ** Licensed under the Apache License, Version 2.0 (the "License");
      6 ** you may not use this file except in compliance with the License.
      7 ** You may obtain a copy of the License at
      8 **
      9 **     http://www.apache.org/licenses/LICENSE-2.0
     10 **
     11 ** Unless required by applicable law or agreed to in writing, software
     12 ** distributed under the License is distributed on an "AS IS" BASIS,
     13 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14 ** See the License for the specific language governing permissions and
     15 ** limitations under the License.
     16 */
     17 
     18 #include <stdio.h>
     19 #include <stdlib.h>
     20 #include <math.h>
     21 
     22 #include "context.h"
     23 #include "primitives.h"
     24 #include "light.h"
     25 #include "matrix.h"
     26 #include "vertex.h"
     27 #include "fp.h"
     28 #include "TextureObjectManager.h"
     29 
     30 extern "C" void iterators0032(const void* that,
     31         int32_t* it, int32_t c0, int32_t c1, int32_t c2);
     32 
     33 namespace android {
     34 
     35 // ----------------------------------------------------------------------------
     36 
     37 static void primitive_point(ogles_context_t* c, vertex_t* v);
     38 static void primitive_line(ogles_context_t* c, vertex_t* v0, vertex_t* v1);
     39 static void primitive_clip_triangle(ogles_context_t* c,
     40         vertex_t* v0, vertex_t* v1, vertex_t* v2);
     41 
     42 static void primitive_nop_point(ogles_context_t* c, vertex_t* v);
     43 static void primitive_nop_line(ogles_context_t* c, vertex_t* v0, vertex_t* v1);
     44 static void primitive_nop_triangle(ogles_context_t* c,
     45         vertex_t* v0, vertex_t* v1, vertex_t* v2);
     46 
     47 static inline bool cull_triangle(ogles_context_t* c,
     48         vertex_t* v0, vertex_t* v1, vertex_t* v2);
     49 
     50 static void lerp_triangle(ogles_context_t* c,
     51         vertex_t* v0, vertex_t* v1, vertex_t* v2);
     52 
     53 static void lerp_texcoords(ogles_context_t* c,
     54         vertex_t* v0, vertex_t* v1, vertex_t* v2);
     55 
     56 static void lerp_texcoords_w(ogles_context_t* c,
     57         vertex_t* v0, vertex_t* v1, vertex_t* v2);
     58 
     59 static void triangle(ogles_context_t* c,
     60         vertex_t* v0, vertex_t* v1, vertex_t* v2);
     61 
     62 static void clip_triangle(ogles_context_t* c,
     63         vertex_t* v0, vertex_t* v1, vertex_t* v2);
     64 
     65 static unsigned int clip_line(ogles_context_t* c,
     66         vertex_t* s, vertex_t* p);
     67 
     68 // ----------------------------------------------------------------------------
     69 #if 0
     70 #pragma mark -
     71 #endif
     72 
     73 static void lightTriangleDarkSmooth(ogles_context_t* c,
     74         vertex_t* v0, vertex_t* v1, vertex_t* v2)
     75 {
     76     if (!(v0->flags & vertex_t::LIT)) {
     77         v0->flags |= vertex_t::LIT;
     78         const GLvoid* cp = c->arrays.color.element(
     79                 v0->index & vertex_cache_t::INDEX_MASK);
     80         c->arrays.color.fetch(c, v0->color.v, cp);
     81     }
     82     if (!(v1->flags & vertex_t::LIT)) {
     83         v1->flags |= vertex_t::LIT;
     84         const GLvoid* cp = c->arrays.color.element(
     85                 v1->index & vertex_cache_t::INDEX_MASK);
     86         c->arrays.color.fetch(c, v1->color.v, cp);
     87     }
     88     if(!(v2->flags & vertex_t::LIT)) {
     89         v2->flags |= vertex_t::LIT;
     90         const GLvoid* cp = c->arrays.color.element(
     91                 v2->index & vertex_cache_t::INDEX_MASK);
     92         c->arrays.color.fetch(c, v2->color.v, cp);
     93     }
     94 }
     95 
     96 static void lightTriangleDarkFlat(ogles_context_t* c,
     97         vertex_t* v0, vertex_t* v1, vertex_t* v2)
     98 {
     99     if (!(v2->flags & vertex_t::LIT)) {
    100         v2->flags |= vertex_t::LIT;
    101         const GLvoid* cp = c->arrays.color.element(
    102                 v2->index & vertex_cache_t::INDEX_MASK);
    103         c->arrays.color.fetch(c, v2->color.v, cp);
    104     }
    105     // configure the rasterizer here, before we clip
    106     c->rasterizer.procs.color4xv(c, v2->color.v);
    107 }
    108 
    109 static void lightTriangleSmooth(ogles_context_t* c,
    110         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    111 {
    112     if (!(v0->flags & vertex_t::LIT))
    113         c->lighting.lightVertex(c, v0);
    114     if (!(v1->flags & vertex_t::LIT))
    115         c->lighting.lightVertex(c, v1);
    116     if(!(v2->flags & vertex_t::LIT))
    117         c->lighting.lightVertex(c, v2);
    118 }
    119 
    120 static void lightTriangleFlat(ogles_context_t* c,
    121         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    122 {
    123     if (!(v2->flags & vertex_t::LIT))
    124         c->lighting.lightVertex(c, v2);
    125     // configure the rasterizer here, before we clip
    126     c->rasterizer.procs.color4xv(c, v2->color.v);
    127 }
    128 
    129 // The fog versions...
    130 
    131 static inline
    132 void lightVertexDarkSmoothFog(ogles_context_t* c, vertex_t* v)
    133 {
    134     if (!(v->flags & vertex_t::LIT)) {
    135         v->flags |= vertex_t::LIT;
    136         v->fog = c->fog.fog(c, v->eye.z);
    137         const GLvoid* cp = c->arrays.color.element(
    138                 v->index & vertex_cache_t::INDEX_MASK);
    139         c->arrays.color.fetch(c, v->color.v, cp);
    140     }
    141 }
    142 static inline
    143 void lightVertexDarkFlatFog(ogles_context_t* c, vertex_t* v)
    144 {
    145     if (!(v->flags & vertex_t::LIT)) {
    146         v->flags |= vertex_t::LIT;
    147         v->fog = c->fog.fog(c, v->eye.z);
    148     }
    149 }
    150 static inline
    151 void lightVertexSmoothFog(ogles_context_t* c, vertex_t* v)
    152 {
    153     if (!(v->flags & vertex_t::LIT)) {
    154         v->fog = c->fog.fog(c, v->eye.z);
    155         c->lighting.lightVertex(c, v);
    156     }
    157 }
    158 
    159 static void lightTriangleDarkSmoothFog(ogles_context_t* c,
    160         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    161 {
    162     lightVertexDarkSmoothFog(c, v0);
    163     lightVertexDarkSmoothFog(c, v1);
    164     lightVertexDarkSmoothFog(c, v2);
    165 }
    166 
    167 static void lightTriangleDarkFlatFog(ogles_context_t* c,
    168         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    169 {
    170     lightVertexDarkFlatFog(c, v0);
    171     lightVertexDarkFlatFog(c, v1);
    172     lightVertexDarkSmoothFog(c, v2);
    173     // configure the rasterizer here, before we clip
    174     c->rasterizer.procs.color4xv(c, v2->color.v);
    175 }
    176 
    177 static void lightTriangleSmoothFog(ogles_context_t* c,
    178         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    179 {
    180     lightVertexSmoothFog(c, v0);
    181     lightVertexSmoothFog(c, v1);
    182     lightVertexSmoothFog(c, v2);
    183 }
    184 
    185 static void lightTriangleFlatFog(ogles_context_t* c,
    186         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    187 {
    188     lightVertexDarkFlatFog(c, v0);
    189     lightVertexDarkFlatFog(c, v1);
    190     lightVertexSmoothFog(c, v2);
    191     // configure the rasterizer here, before we clip
    192     c->rasterizer.procs.color4xv(c, v2->color.v);
    193 }
    194 
    195 
    196 
    197 typedef void (*light_primitive_t)(ogles_context_t*,
    198         vertex_t*, vertex_t*, vertex_t*);
    199 
    200 // fog 0x4, light 0x2, smooth 0x1
    201 static const light_primitive_t lightPrimitive[8] = {
    202     lightTriangleDarkFlat,          // no fog | dark  | flat
    203     lightTriangleDarkSmooth,        // no fog | dark  | smooth
    204     lightTriangleFlat,              // no fog | light | flat
    205     lightTriangleSmooth,            // no fog | light | smooth
    206     lightTriangleDarkFlatFog,       // fog    | dark  | flat
    207     lightTriangleDarkSmoothFog,     // fog    | dark  | smooth
    208     lightTriangleFlatFog,           // fog    | light | flat
    209     lightTriangleSmoothFog          // fog    | light | smooth
    210 };
    211 
    212 void ogles_validate_primitives(ogles_context_t* c)
    213 {
    214     const uint32_t enables = c->rasterizer.state.enables;
    215 
    216     // set up the lighting/shading/smoothing/fogging function
    217     int index = enables & GGL_ENABLE_SMOOTH ? 0x1 : 0;
    218     index |= c->lighting.enable ? 0x2 : 0;
    219     index |= enables & GGL_ENABLE_FOG ? 0x4 : 0;
    220     c->lighting.lightTriangle = lightPrimitive[index];
    221 
    222     // set up the primitive renderers
    223     if (ggl_likely(c->arrays.vertex.enable)) {
    224         c->prims.renderPoint    = primitive_point;
    225         c->prims.renderLine     = primitive_line;
    226         c->prims.renderTriangle = primitive_clip_triangle;
    227     } else {
    228         c->prims.renderPoint    = primitive_nop_point;
    229         c->prims.renderLine     = primitive_nop_line;
    230         c->prims.renderTriangle = primitive_nop_triangle;
    231     }
    232 }
    233 
    234 // ----------------------------------------------------------------------------
    235 
    236 void compute_iterators_t::initTriangle(
    237         vertex_t const* v0, vertex_t const* v1, vertex_t const* v2)
    238 {
    239     m_dx01 = v1->window.x - v0->window.x;
    240     m_dy10 = v0->window.y - v1->window.y;
    241     m_dx20 = v0->window.x - v2->window.x;
    242     m_dy02 = v2->window.y - v0->window.y;
    243     m_area = m_dx01*m_dy02 + (-m_dy10)*m_dx20;
    244 }
    245 
    246 void compute_iterators_t::initLine(
    247         vertex_t const* v0, vertex_t const* v1)
    248 {
    249     m_dx01 = m_dy02 = v1->window.x - v0->window.x;
    250     m_dy10 = m_dx20 = v0->window.y - v1->window.y;
    251     m_area = m_dx01*m_dy02 + (-m_dy10)*m_dx20;
    252 }
    253 
    254 void compute_iterators_t::initLerp(vertex_t const* v0, uint32_t enables)
    255 {
    256     m_x0 = v0->window.x;
    257     m_y0 = v0->window.y;
    258     const GGLcoord area = (m_area + TRI_HALF) >> TRI_FRACTION_BITS;
    259     const GGLcoord minArea = 2; // cannot be inverted
    260     // triangles with an area smaller than 1.0 are not smooth-shaded
    261 
    262     int q=0, s=0, d=0;
    263     if (abs(area) >= minArea) {
    264         // Here we do some voodoo magic, to compute a suitable scale
    265         // factor for deltas/area:
    266 
    267         // First compute the 1/area with full 32-bits precision,
    268         // gglRecipQNormalized returns a number [-0.5, 0.5[ and an exponent.
    269         d = gglRecipQNormalized(area, &q);
    270 
    271         // Then compute the minimum left-shift to not overflow the muls
    272         // below.
    273         s = 32 - gglClz(abs(m_dy02)|abs(m_dy10)|abs(m_dx01)|abs(m_dx20));
    274 
    275         // We'll keep 16-bits of precision for deltas/area. So we need
    276         // to shift everything left an extra 15 bits.
    277         s += 15;
    278 
    279         // make sure all final shifts are not > 32, because gglMulx
    280         // can't handle it.
    281         if (s < q) s = q;
    282         if (s > 32) {
    283             d >>= 32-s;
    284             s = 32;
    285         }
    286     }
    287 
    288     m_dx01 = gglMulx(m_dx01, d, s);
    289     m_dy10 = gglMulx(m_dy10, d, s);
    290     m_dx20 = gglMulx(m_dx20, d, s);
    291     m_dy02 = gglMulx(m_dy02, d, s);
    292     m_area_scale = 32 + q - s;
    293     m_scale = 0;
    294 
    295     if (enables & GGL_ENABLE_TMUS) {
    296         const int A = gglClz(abs(m_dy02)|abs(m_dy10)|abs(m_dx01)|abs(m_dx20));
    297         const int B = gglClz(abs(m_x0)|abs(m_y0));
    298         m_scale = max(0, 32 - (A + 16)) +
    299                   max(0, 32 - (B + TRI_FRACTION_BITS)) + 1;
    300     }
    301 }
    302 
    303 int compute_iterators_t::iteratorsScale(GGLfixed* it,
    304         int32_t c0, int32_t c1, int32_t c2) const
    305 {
    306     int32_t dc01 = c1 - c0;
    307     int32_t dc02 = c2 - c0;
    308     const int A = gglClz(abs(c0));
    309     const int B = gglClz(abs(dc01)|abs(dc02));
    310     const int scale = min(A, B - m_scale) - 2;
    311     if (scale >= 0) {
    312         c0   <<= scale;
    313         dc01 <<= scale;
    314         dc02 <<= scale;
    315     } else {
    316         c0   >>= -scale;
    317         dc01 >>= -scale;
    318         dc02 >>= -scale;
    319     }
    320     const int s = m_area_scale;
    321     int32_t dcdx = gglMulAddx(dc01, m_dy02, gglMulx(dc02, m_dy10, s), s);
    322     int32_t dcdy = gglMulAddx(dc02, m_dx01, gglMulx(dc01, m_dx20, s), s);
    323     int32_t c = c0 - (gglMulAddx(dcdx, m_x0,
    324             gglMulx(dcdy, m_y0, TRI_FRACTION_BITS), TRI_FRACTION_BITS));
    325     it[0] = c;
    326     it[1] = dcdx;
    327     it[2] = dcdy;
    328     return scale;
    329 }
    330 
    331 void compute_iterators_t::iterators1616(GGLfixed* it,
    332         GGLfixed c0, GGLfixed c1, GGLfixed c2) const
    333 {
    334     const GGLfixed dc01 = c1 - c0;
    335     const GGLfixed dc02 = c2 - c0;
    336     // 16.16 x 16.16 == 32.32 --> 16.16
    337     const int s = m_area_scale;
    338     int32_t dcdx = gglMulAddx(dc01, m_dy02, gglMulx(dc02, m_dy10, s), s);
    339     int32_t dcdy = gglMulAddx(dc02, m_dx01, gglMulx(dc01, m_dx20, s), s);
    340     int32_t c = c0 - (gglMulAddx(dcdx, m_x0,
    341             gglMulx(dcdy, m_y0, TRI_FRACTION_BITS), TRI_FRACTION_BITS));
    342     it[0] = c;
    343     it[1] = dcdx;
    344     it[2] = dcdy;
    345 }
    346 
    347 void compute_iterators_t::iterators0032(int64_t* it,
    348         int32_t c0, int32_t c1, int32_t c2) const
    349 {
    350     const int s = m_area_scale - 16;
    351     int32_t dc01 = (c1 - c0)>>s;
    352     int32_t dc02 = (c2 - c0)>>s;
    353     // 16.16 x 16.16 == 32.32
    354     int64_t dcdx = gglMulii(dc01, m_dy02) + gglMulii(dc02, m_dy10);
    355     int64_t dcdy = gglMulii(dc02, m_dx01) + gglMulii(dc01, m_dx20);
    356     it[ 0] = (c0<<16) - ((dcdx*m_x0 + dcdy*m_y0)>>4);
    357     it[ 1] = dcdx;
    358     it[ 2] = dcdy;
    359 }
    360 
    361 #if defined(__arm__) && !defined(__thumb__)
    362 inline void compute_iterators_t::iterators0032(int32_t* it,
    363         int32_t c0, int32_t c1, int32_t c2) const
    364 {
    365     ::iterators0032(this, it, c0, c1, c2);
    366 }
    367 #else
    368 void compute_iterators_t::iterators0032(int32_t* it,
    369         int32_t c0, int32_t c1, int32_t c2) const
    370 {
    371     int64_t it64[3];
    372     iterators0032(it64, c0, c1, c2);
    373     it[0] = it64[0];
    374     it[1] = it64[1];
    375     it[2] = it64[2];
    376 }
    377 #endif
    378 
    379 // ----------------------------------------------------------------------------
    380 
    381 static inline int32_t clampZ(GLfixed z) CONST;
    382 int32_t clampZ(GLfixed z) {
    383     z = (z & ~(z>>31));
    384     if (z >= 0x10000)
    385         z = 0xFFFF;
    386     return z;
    387 }
    388 
    389 static __attribute__((noinline))
    390 void fetch_texcoord_impl(ogles_context_t* c,
    391         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    392 {
    393     vertex_t* const vtx[3] = { v0, v1, v2 };
    394     array_t const * const texcoordArray = c->arrays.texture;
    395 
    396     for (int i=0 ; i<GGL_TEXTURE_UNIT_COUNT ; i++) {
    397         if (!(c->rasterizer.state.texture[i].enable))
    398             continue;
    399 
    400         for (int j=0 ; j<3 ; j++) {
    401             vertex_t* const v = vtx[j];
    402             if (v->flags & vertex_t::TT)
    403                 continue;
    404 
    405             // NOTE: here we could compute automatic texgen
    406             // such as sphere/cube maps, instead of fetching them
    407             // from the textcoord array.
    408 
    409             vec4_t& coords = v->texture[i];
    410             const GLubyte* tp = texcoordArray[i].element(
    411                     v->index & vertex_cache_t::INDEX_MASK);
    412             texcoordArray[i].fetch(c, coords.v, tp);
    413 
    414             // transform texture coordinates...
    415             coords.Q = 0x10000;
    416             const transform_t& tr = c->transforms.texture[i].transform;
    417             if (ggl_unlikely(tr.ops)) {
    418                 c->arrays.tex_transform[i](&tr, &coords, &coords);
    419             }
    420 
    421             // divide by Q
    422             const GGLfixed q = coords.Q;
    423             if (ggl_unlikely(q != 0x10000)) {
    424                 const int32_t qinv = gglRecip28(q);
    425                 coords.S = gglMulx(coords.S, qinv, 28);
    426                 coords.T = gglMulx(coords.T, qinv, 28);
    427             }
    428         }
    429     }
    430     v0->flags |= vertex_t::TT;
    431     v1->flags |= vertex_t::TT;
    432     v2->flags |= vertex_t::TT;
    433 }
    434 
    435 inline void fetch_texcoord(ogles_context_t* c,
    436         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    437 {
    438     const uint32_t enables = c->rasterizer.state.enables;
    439     if (!(enables & GGL_ENABLE_TMUS))
    440         return;
    441 
    442     // Fetch & transform texture coordinates...
    443     if (ggl_likely(v0->flags & v1->flags & v2->flags & vertex_t::TT)) {
    444         // already done for all three vertices, bail...
    445         return;
    446     }
    447     fetch_texcoord_impl(c, v0, v1, v2);
    448 }
    449 
    450 // ----------------------------------------------------------------------------
    451 #if 0
    452 #pragma mark -
    453 #pragma mark Point
    454 #endif
    455 
    456 void primitive_nop_point(ogles_context_t*, vertex_t*) {
    457 }
    458 
    459 void primitive_point(ogles_context_t* c, vertex_t* v)
    460 {
    461     // lighting & clamping...
    462     const uint32_t enables = c->rasterizer.state.enables;
    463 
    464     if (ggl_unlikely(!(v->flags & vertex_t::LIT))) {
    465         if (c->lighting.enable) {
    466             c->lighting.lightVertex(c, v);
    467         } else {
    468             v->flags |= vertex_t::LIT;
    469             const GLvoid* cp = c->arrays.color.element(
    470                     v->index & vertex_cache_t::INDEX_MASK);
    471             c->arrays.color.fetch(c, v->color.v, cp);
    472         }
    473         if (enables & GGL_ENABLE_FOG) {
    474             v->fog = c->fog.fog(c, v->eye.z);
    475         }
    476     }
    477 
    478     // XXX: we don't need to do that each-time
    479     // if color array and lighting not enabled
    480     c->rasterizer.procs.color4xv(c, v->color.v);
    481 
    482     // XXX: look into ES point-sprite extension
    483     if (enables & GGL_ENABLE_TMUS) {
    484         fetch_texcoord(c, v,v,v);
    485         for (int i=0 ; i<GGL_TEXTURE_UNIT_COUNT ; i++) {
    486             if (!c->rasterizer.state.texture[i].enable)
    487                 continue;
    488             int32_t itt[8];
    489             itt[1] = itt[2] = itt[4] = itt[5] = 0;
    490             itt[6] = itt[7] = 16; // XXX: check that
    491             if (c->rasterizer.state.texture[i].s_wrap == GGL_CLAMP) {
    492                 int width = c->textures.tmu[i].texture->surface.width;
    493                 itt[0] = v->texture[i].S * width;
    494                 itt[6] = 0;
    495             }
    496             if (c->rasterizer.state.texture[i].t_wrap == GGL_CLAMP) {
    497                 int height = c->textures.tmu[i].texture->surface.height;
    498                 itt[3] = v->texture[i].T * height;
    499                 itt[7] = 0;
    500             }
    501             c->rasterizer.procs.texCoordGradScale8xv(c, i, itt);
    502         }
    503     }
    504 
    505     if (enables & GGL_ENABLE_DEPTH_TEST) {
    506         int32_t itz[3];
    507         itz[0] = clampZ(v->window.z) * 0x00010001;
    508         itz[1] = itz[2] = 0;
    509         c->rasterizer.procs.zGrad3xv(c, itz);
    510     }
    511 
    512     if (enables & GGL_ENABLE_FOG) {
    513         GLfixed itf[3];
    514         itf[0] = v->fog;
    515         itf[1] = itf[2] = 0;
    516         c->rasterizer.procs.fogGrad3xv(c, itf);
    517     }
    518 
    519     // Render our point...
    520     c->rasterizer.procs.pointx(c, v->window.v, c->point.size);
    521 }
    522 
    523 // ----------------------------------------------------------------------------
    524 #if 0
    525 #pragma mark -
    526 #pragma mark Line
    527 #endif
    528 
    529 void primitive_nop_line(ogles_context_t*, vertex_t*, vertex_t*) {
    530 }
    531 
    532 void primitive_line(ogles_context_t* c, vertex_t* v0, vertex_t* v1)
    533 {
    534     // get texture coordinates
    535     fetch_texcoord(c, v0, v1, v1);
    536 
    537     // light/shade the vertices first (they're copied below)
    538     c->lighting.lightTriangle(c, v0, v1, v1);
    539 
    540     // clip the line if needed
    541     if (ggl_unlikely((v0->flags | v1->flags) & vertex_t::CLIP_ALL)) {
    542         unsigned int count = clip_line(c, v0, v1);
    543         if (ggl_unlikely(count == 0))
    544             return;
    545     }
    546 
    547     // compute iterators...
    548     const uint32_t enables = c->rasterizer.state.enables;
    549     const uint32_t mask =   GGL_ENABLE_TMUS |
    550                             GGL_ENABLE_SMOOTH |
    551                             GGL_ENABLE_W |
    552                             GGL_ENABLE_FOG |
    553                             GGL_ENABLE_DEPTH_TEST;
    554 
    555     if (ggl_unlikely(enables & mask)) {
    556         c->lerp.initLine(v0, v1);
    557         lerp_triangle(c, v0, v1, v0);
    558     }
    559 
    560     // render our line
    561     c->rasterizer.procs.linex(c, v0->window.v, v1->window.v, c->line.width);
    562 }
    563 
    564 // ----------------------------------------------------------------------------
    565 #if 0
    566 #pragma mark -
    567 #pragma mark Triangle
    568 #endif
    569 
    570 void primitive_nop_triangle(ogles_context_t* c,
    571         vertex_t* v0, vertex_t* v1, vertex_t* v2) {
    572 }
    573 
    574 void primitive_clip_triangle(ogles_context_t* c,
    575         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    576 {
    577     uint32_t cc = (v0->flags | v1->flags | v2->flags) & vertex_t::CLIP_ALL;
    578     if (ggl_likely(!cc)) {
    579         // code below must be as optimized as possible, this is the
    580         // common code path.
    581 
    582         // This triangle is not clipped, test if it's culled
    583         // unclipped triangle...
    584         c->lerp.initTriangle(v0, v1, v2);
    585         if (cull_triangle(c, v0, v1, v2))
    586             return; // culled!
    587 
    588         // Fetch all texture coordinates if needed
    589         fetch_texcoord(c, v0, v1, v2);
    590 
    591         // light (or shade) our triangle!
    592         c->lighting.lightTriangle(c, v0, v1, v2);
    593 
    594         triangle(c, v0, v1, v2);
    595         return;
    596     }
    597 
    598     // The assumption here is that we're not going to clip very often,
    599     // and even more rarely will we clip a triangle that ends up
    600     // being culled out. So it's okay to light the vertices here, even though
    601     // in a few cases we won't render the triangle (if culled).
    602 
    603     // Fetch texture coordinates...
    604     fetch_texcoord(c, v0, v1, v2);
    605 
    606     // light (or shade) our triangle!
    607     c->lighting.lightTriangle(c, v0, v1, v2);
    608 
    609     clip_triangle(c, v0, v1, v2);
    610 }
    611 
    612 // -----------------------------------------------------------------------
    613 
    614 void triangle(ogles_context_t* c,
    615         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    616 {
    617     // compute iterators...
    618     const uint32_t enables = c->rasterizer.state.enables;
    619     const uint32_t mask =   GGL_ENABLE_TMUS |
    620                             GGL_ENABLE_SMOOTH |
    621                             GGL_ENABLE_W |
    622                             GGL_ENABLE_FOG |
    623                             GGL_ENABLE_DEPTH_TEST;
    624 
    625     if (ggl_likely(enables & mask))
    626         lerp_triangle(c, v0, v1, v2);
    627 
    628     c->rasterizer.procs.trianglex(c, v0->window.v, v1->window.v, v2->window.v);
    629 }
    630 
    631 void lerp_triangle(ogles_context_t* c,
    632         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    633 {
    634     const uint32_t enables = c->rasterizer.state.enables;
    635     c->lerp.initLerp(v0, enables);
    636 
    637     // set up texture iterators
    638     if (enables & GGL_ENABLE_TMUS) {
    639         if (enables & GGL_ENABLE_W) {
    640             lerp_texcoords_w(c, v0, v1, v2);
    641         } else {
    642             lerp_texcoords(c, v0, v1, v2);
    643         }
    644     }
    645 
    646     // set up the color iterators
    647     const compute_iterators_t& lerp = c->lerp;
    648     if (enables & GGL_ENABLE_SMOOTH) {
    649         GLfixed itc[12];
    650         for (int i=0 ; i<4 ; i++) {
    651             const GGLcolor c0 = v0->color.v[i] * 255;
    652             const GGLcolor c1 = v1->color.v[i] * 255;
    653             const GGLcolor c2 = v2->color.v[i] * 255;
    654             lerp.iterators1616(&itc[i*3], c0, c1, c2);
    655         }
    656         c->rasterizer.procs.colorGrad12xv(c, itc);
    657     }
    658 
    659     if (enables & GGL_ENABLE_DEPTH_TEST) {
    660         int32_t itz[3];
    661         const int32_t v0z = clampZ(v0->window.z);
    662         const int32_t v1z = clampZ(v1->window.z);
    663         const int32_t v2z = clampZ(v2->window.z);
    664         if (ggl_unlikely(c->polygonOffset.enable)) {
    665             const int32_t units = (c->polygonOffset.units << 16);
    666             const GLfixed factor = c->polygonOffset.factor;
    667             if (factor) {
    668                 int64_t itz64[3];
    669                 lerp.iterators0032(itz64, v0z, v1z, v2z);
    670                 int64_t maxDepthSlope = max(itz64[1], itz64[2]);
    671                 itz[0] = uint32_t(itz64[0])
    672                         + uint32_t((maxDepthSlope*factor)>>16) + units;
    673                 itz[1] = uint32_t(itz64[1]);
    674                 itz[2] = uint32_t(itz64[2]);
    675             } else {
    676                 lerp.iterators0032(itz, v0z, v1z, v2z);
    677                 itz[0] += units;
    678             }
    679         } else {
    680             lerp.iterators0032(itz, v0z, v1z, v2z);
    681         }
    682         c->rasterizer.procs.zGrad3xv(c, itz);
    683     }
    684 
    685     if (ggl_unlikely(enables & GGL_ENABLE_FOG)) {
    686         GLfixed itf[3];
    687         lerp.iterators1616(itf, v0->fog, v1->fog, v2->fog);
    688         c->rasterizer.procs.fogGrad3xv(c, itf);
    689     }
    690 }
    691 
    692 
    693 static inline
    694 int compute_lod(ogles_context_t* c, int i,
    695         int32_t s0, int32_t t0, int32_t s1, int32_t t1, int32_t s2, int32_t t2)
    696 {
    697     // Compute mipmap level / primitive
    698     // rho = sqrt( texelArea / area )
    699     // lod = log2( rho )
    700     // lod = log2( texelArea / area ) / 2
    701     // lod = (log2( texelArea ) - log2( area )) / 2
    702     const compute_iterators_t& lerp = c->lerp;
    703     const GGLcoord area = abs(lerp.area());
    704     const int w = c->textures.tmu[i].texture->surface.width;
    705     const int h = c->textures.tmu[i].texture->surface.height;
    706     const int shift = 16 + (16 - TRI_FRACTION_BITS);
    707     int32_t texelArea = abs( gglMulx(s1-s0, t2-t0, shift) -
    708             gglMulx(s2-s0, t1-t0, shift) )*w*h;
    709     int log2TArea = (32-TRI_FRACTION_BITS  -1) - gglClz(texelArea);
    710     int log2Area  = (32-TRI_FRACTION_BITS*2-1) - gglClz(area);
    711     int lod = (log2TArea - log2Area + 1) >> 1;
    712     return lod;
    713 }
    714 
    715 void lerp_texcoords(ogles_context_t* c,
    716         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    717 {
    718     const compute_iterators_t& lerp = c->lerp;
    719     int32_t itt[8] __attribute__((aligned(16)));
    720     for (int i=0 ; i<GGL_TEXTURE_UNIT_COUNT ; i++) {
    721         const texture_t& tmu = c->rasterizer.state.texture[i];
    722         if (!tmu.enable)
    723             continue;
    724 
    725         // compute the jacobians using block floating-point
    726         int32_t s0 = v0->texture[i].S;
    727         int32_t t0 = v0->texture[i].T;
    728         int32_t s1 = v1->texture[i].S;
    729         int32_t t1 = v1->texture[i].T;
    730         int32_t s2 = v2->texture[i].S;
    731         int32_t t2 = v2->texture[i].T;
    732 
    733         const GLenum min_filter = c->textures.tmu[i].texture->min_filter;
    734         if (ggl_unlikely(min_filter >= GL_NEAREST_MIPMAP_NEAREST)) {
    735             int lod = compute_lod(c, i, s0, t0, s1, t1, s2, t2);
    736             c->rasterizer.procs.bindTextureLod(c, i,
    737                     &c->textures.tmu[i].texture->mip(lod));
    738         }
    739 
    740         // premultiply (s,t) when clampling
    741         if (tmu.s_wrap == GGL_CLAMP) {
    742             const int width = tmu.surface.width;
    743             s0 *= width;
    744             s1 *= width;
    745             s2 *= width;
    746         }
    747         if (tmu.t_wrap == GGL_CLAMP) {
    748             const int height = tmu.surface.height;
    749             t0 *= height;
    750             t1 *= height;
    751             t2 *= height;
    752         }
    753         itt[6] = -lerp.iteratorsScale(itt+0, s0, s1, s2);
    754         itt[7] = -lerp.iteratorsScale(itt+3, t0, t1, t2);
    755         c->rasterizer.procs.texCoordGradScale8xv(c, i, itt);
    756     }
    757 }
    758 
    759 void lerp_texcoords_w(ogles_context_t* c,
    760         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    761 {
    762     const compute_iterators_t& lerp = c->lerp;
    763     int32_t itt[8] __attribute__((aligned(16)));
    764     int32_t itw[3];
    765 
    766     // compute W's scale to 2.30
    767     int32_t w0 = v0->window.w;
    768     int32_t w1 = v1->window.w;
    769     int32_t w2 = v2->window.w;
    770     int wscale = 32 - gglClz(w0|w1|w2);
    771 
    772     // compute the jacobian using block floating-point
    773     int sc = lerp.iteratorsScale(itw, w0, w1, w2);
    774     sc +=  wscale - 16;
    775     c->rasterizer.procs.wGrad3xv(c, itw);
    776 
    777     for (int i=0 ; i<GGL_TEXTURE_UNIT_COUNT ; i++) {
    778         const texture_t& tmu = c->rasterizer.state.texture[i];
    779         if (!tmu.enable)
    780             continue;
    781 
    782         // compute the jacobians using block floating-point
    783         int32_t s0 = v0->texture[i].S;
    784         int32_t t0 = v0->texture[i].T;
    785         int32_t s1 = v1->texture[i].S;
    786         int32_t t1 = v1->texture[i].T;
    787         int32_t s2 = v2->texture[i].S;
    788         int32_t t2 = v2->texture[i].T;
    789 
    790         const GLenum min_filter = c->textures.tmu[i].texture->min_filter;
    791         if (ggl_unlikely(min_filter >= GL_NEAREST_MIPMAP_NEAREST)) {
    792             int lod = compute_lod(c, i, s0, t0, s1, t1, s2, t2);
    793             c->rasterizer.procs.bindTextureLod(c, i,
    794                     &c->textures.tmu[i].texture->mip(lod));
    795         }
    796 
    797         // premultiply (s,t) when clampling
    798         if (tmu.s_wrap == GGL_CLAMP) {
    799             const int width = tmu.surface.width;
    800             s0 *= width;
    801             s1 *= width;
    802             s2 *= width;
    803         }
    804         if (tmu.t_wrap == GGL_CLAMP) {
    805             const int height = tmu.surface.height;
    806             t0 *= height;
    807             t1 *= height;
    808             t2 *= height;
    809         }
    810 
    811         s0 = gglMulx(s0, w0, wscale);
    812         t0 = gglMulx(t0, w0, wscale);
    813         s1 = gglMulx(s1, w1, wscale);
    814         t1 = gglMulx(t1, w1, wscale);
    815         s2 = gglMulx(s2, w2, wscale);
    816         t2 = gglMulx(t2, w2, wscale);
    817 
    818         itt[6] = sc - lerp.iteratorsScale(itt+0, s0, s1, s2);
    819         itt[7] = sc - lerp.iteratorsScale(itt+3, t0, t1, t2);
    820         c->rasterizer.procs.texCoordGradScale8xv(c, i, itt);
    821     }
    822 }
    823 
    824 
    825 static inline
    826 bool cull_triangle(ogles_context_t* c, vertex_t* v0, vertex_t* v1, vertex_t* v2)
    827 {
    828     if (ggl_likely(c->cull.enable)) {
    829         const GLenum winding = (c->lerp.area() > 0) ? GL_CW : GL_CCW;
    830         const GLenum face = (winding == c->cull.frontFace) ? GL_FRONT : GL_BACK;
    831         if (face == c->cull.cullFace)
    832             return true; // culled!
    833     }
    834     return false;
    835 }
    836 
    837 static inline
    838 GLfixed frustumPlaneDist(int plane, const vec4_t& s)
    839 {
    840     const GLfixed d = s.v[ plane >> 1 ];
    841     return  ((plane & 1) ? (s.w - d) : (s.w + d));
    842 }
    843 
    844 static inline
    845 int32_t clipDivide(GLfixed a, GLfixed b) {
    846     // returns a 4.28 fixed-point
    847     return gglMulDivi(1LU<<28, a, b);
    848 }
    849 
    850 void clip_triangle(ogles_context_t* c,
    851         vertex_t* v0, vertex_t* v1, vertex_t* v2)
    852 {
    853     uint32_t all_cc = (v0->flags | v1->flags | v2->flags) & vertex_t::CLIP_ALL;
    854 
    855     vertex_t *p0, *p1, *p2;
    856     const int MAX_CLIPPING_PLANES = 6 + OGLES_MAX_CLIP_PLANES;
    857     const int MAX_VERTICES = 3;
    858 
    859     // Temporary buffer to hold the new vertices. Each plane can add up to
    860     // two new vertices (because the polygon is convex).
    861     // We need one extra element, to handle an overflow case when
    862     // the polygon degenerates into something non convex.
    863     vertex_t buffer[MAX_CLIPPING_PLANES * 2 + 1];   // ~3KB
    864     vertex_t* buf = buffer;
    865 
    866     // original list of vertices (polygon to clip, in fact this
    867     // function works with an arbitrary polygon).
    868     vertex_t* in[3] = { v0, v1, v2 };
    869 
    870     // output lists (we need 2, which we use back and forth)
    871     // (maximum outpout list's size is MAX_CLIPPING_PLANES + MAX_VERTICES)
    872     // 2 more elements for overflow when non convex polygons.
    873     vertex_t* out[2][MAX_CLIPPING_PLANES + MAX_VERTICES + 2];
    874     unsigned int outi = 0;
    875 
    876     // current input list
    877     vertex_t** ivl = in;
    878 
    879     // 3 input vertices, 0 in the output list, first plane
    880     unsigned int ic = 3;
    881 
    882     // User clip-planes first, the clipping is always done in eye-coordinate
    883     // this is basically the same algorithm than for the view-volume
    884     // clipping, except for the computation of the distance (vertex, plane)
    885     // and the fact that we need to compute the eye-coordinates of each
    886     // new vertex we create.
    887 
    888     if (ggl_unlikely(all_cc & vertex_t::USER_CLIP_ALL))
    889     {
    890         unsigned int plane = 0;
    891         uint32_t cc = (all_cc & vertex_t::USER_CLIP_ALL) >> 8;
    892         do {
    893             if (cc & 1) {
    894                 // pointers to our output list (head and current)
    895                 vertex_t** const ovl = &out[outi][0];
    896                 vertex_t** output = ovl;
    897                 unsigned int oc = 0;
    898                 unsigned int sentinel = 0;
    899                 // previous vertex, compute distance to the plane
    900                 vertex_t* s = ivl[ic-1];
    901                 const vec4_t& equation = c->clipPlanes.plane[plane].equation;
    902                 GLfixed sd = dot4(equation.v, s->eye.v);
    903                 // clip each vertex against this plane...
    904                 for (unsigned int i=0 ; i<ic ; i++) {
    905                     vertex_t* p = ivl[i];
    906                     const GLfixed pd = dot4(equation.v, p->eye.v);
    907                     if (sd >= 0) {
    908                         if (pd >= 0) {
    909                             // both inside
    910                             *output++ = p;
    911                             oc++;
    912                         } else {
    913                             // s inside, p outside (exiting)
    914                             const GLfixed t = clipDivide(sd, sd-pd);
    915                             c->arrays.clipEye(c, buf, t, p, s);
    916                             *output++ = buf++;
    917                             oc++;
    918                             if (++sentinel >= 3)
    919                                 return; // non-convex polygon!
    920                         }
    921                     } else {
    922                         if (pd >= 0) {
    923                             // s outside (entering)
    924                             if (pd) {
    925                                 const GLfixed t = clipDivide(pd, pd-sd);
    926                                 c->arrays.clipEye(c, buf, t, s, p);
    927                                 *output++ = buf++;
    928                                 oc++;
    929                                 if (++sentinel >= 3)
    930                                     return; // non-convex polygon!
    931                             }
    932                             *output++ = p;
    933                             oc++;
    934                         } else {
    935                            // both outside
    936                         }
    937                     }
    938                     s = p;
    939                     sd = pd;
    940                 }
    941                 // output list become the new input list
    942                 if (oc<3)
    943                     return; // less than 3 vertices left? we're done!
    944                 ivl = ovl;
    945                 ic = oc;
    946                 outi = 1-outi;
    947             }
    948             cc >>= 1;
    949             plane++;
    950         } while (cc);
    951     }
    952 
    953     // frustum clip-planes
    954     if (all_cc & vertex_t::FRUSTUM_CLIP_ALL)
    955     {
    956         unsigned int plane = 0;
    957         uint32_t cc = all_cc & vertex_t::FRUSTUM_CLIP_ALL;
    958         do {
    959             if (cc & 1) {
    960                 // pointers to our output list (head and current)
    961                 vertex_t** const ovl = &out[outi][0];
    962                 vertex_t** output = ovl;
    963                 unsigned int oc = 0;
    964                 unsigned int sentinel = 0;
    965                 // previous vertex, compute distance to the plane
    966                 vertex_t* s = ivl[ic-1];
    967                 GLfixed sd = frustumPlaneDist(plane, s->clip);
    968                 // clip each vertex against this plane...
    969                 for (unsigned int i=0 ; i<ic ; i++) {
    970                     vertex_t* p = ivl[i];
    971                     const GLfixed pd = frustumPlaneDist(plane, p->clip);
    972                     if (sd >= 0) {
    973                         if (pd >= 0) {
    974                             // both inside
    975                             *output++ = p;
    976                             oc++;
    977                         } else {
    978                             // s inside, p outside (exiting)
    979                             const GLfixed t = clipDivide(sd, sd-pd);
    980                             c->arrays.clipVertex(c, buf, t, p, s);
    981                             *output++ = buf++;
    982                             oc++;
    983                             if (++sentinel >= 3)
    984                                 return; // non-convex polygon!
    985                         }
    986                     } else {
    987                         if (pd >= 0) {
    988                             // s outside (entering)
    989                             if (pd) {
    990                                 const GLfixed t = clipDivide(pd, pd-sd);
    991                                 c->arrays.clipVertex(c, buf, t, s, p);
    992                                 *output++ = buf++;
    993                                 oc++;
    994                                 if (++sentinel >= 3)
    995                                     return; // non-convex polygon!
    996                             }
    997                             *output++ = p;
    998                             oc++;
    999                         } else {
   1000                            // both outside
   1001                         }
   1002                     }
   1003                     s = p;
   1004                     sd = pd;
   1005                 }
   1006                 // output list become the new input list
   1007                 if (oc<3)
   1008                     return; // less than 3 vertices left? we're done!
   1009                 ivl = ovl;
   1010                 ic = oc;
   1011                 outi = 1-outi;
   1012             }
   1013             cc >>= 1;
   1014             plane++;
   1015         } while (cc);
   1016     }
   1017 
   1018     // finally we can render our triangles...
   1019     p0 = ivl[0];
   1020     p1 = ivl[1];
   1021     for (unsigned int i=2 ; i<ic ; i++) {
   1022         p2 = ivl[i];
   1023         c->lerp.initTriangle(p0, p1, p2);
   1024         if (cull_triangle(c, p0, p1, p2)) {
   1025             p1 = p2;
   1026             continue; // culled!
   1027         }
   1028         triangle(c, p0, p1, p2);
   1029         p1 = p2;
   1030     }
   1031 }
   1032 
   1033 unsigned int clip_line(ogles_context_t* c, vertex_t* s, vertex_t* p)
   1034 {
   1035     const uint32_t all_cc = (s->flags | p->flags) & vertex_t::CLIP_ALL;
   1036 
   1037     if (ggl_unlikely(all_cc & vertex_t::USER_CLIP_ALL))
   1038     {
   1039         unsigned int plane = 0;
   1040         uint32_t cc = (all_cc & vertex_t::USER_CLIP_ALL) >> 8;
   1041         do {
   1042             if (cc & 1) {
   1043                 const vec4_t& equation = c->clipPlanes.plane[plane].equation;
   1044                 const GLfixed sd = dot4(equation.v, s->eye.v);
   1045                 const GLfixed pd = dot4(equation.v, p->eye.v);
   1046                 if (sd >= 0) {
   1047                     if (pd >= 0) {
   1048                         // both inside
   1049                     } else {
   1050                         // s inside, p outside (exiting)
   1051                         const GLfixed t = clipDivide(sd, sd-pd);
   1052                         c->arrays.clipEye(c, p, t, p, s);
   1053                     }
   1054                 } else {
   1055                     if (pd >= 0) {
   1056                         // s outside (entering)
   1057                         if (pd) {
   1058                             const GLfixed t = clipDivide(pd, pd-sd);
   1059                             c->arrays.clipEye(c, s, t, s, p);
   1060                         }
   1061                     } else {
   1062                        // both outside
   1063                        return 0;
   1064                     }
   1065                 }
   1066             }
   1067             cc >>= 1;
   1068             plane++;
   1069         } while (cc);
   1070     }
   1071 
   1072     // frustum clip-planes
   1073     if (all_cc & vertex_t::FRUSTUM_CLIP_ALL)
   1074     {
   1075         unsigned int plane = 0;
   1076         uint32_t cc = all_cc & vertex_t::FRUSTUM_CLIP_ALL;
   1077         do {
   1078             if (cc & 1) {
   1079                 const GLfixed sd = frustumPlaneDist(plane, s->clip);
   1080                 const GLfixed pd = frustumPlaneDist(plane, p->clip);
   1081                 if (sd >= 0) {
   1082                     if (pd >= 0) {
   1083                         // both inside
   1084                     } else {
   1085                         // s inside, p outside (exiting)
   1086                         const GLfixed t = clipDivide(sd, sd-pd);
   1087                         c->arrays.clipVertex(c, p, t, p, s);
   1088                     }
   1089                 } else {
   1090                     if (pd >= 0) {
   1091                         // s outside (entering)
   1092                         if (pd) {
   1093                             const GLfixed t = clipDivide(pd, pd-sd);
   1094                             c->arrays.clipVertex(c, s, t, s, p);
   1095                         }
   1096                     } else {
   1097                        // both outside
   1098                        return 0;
   1099                     }
   1100                 }
   1101             }
   1102             cc >>= 1;
   1103             plane++;
   1104         } while (cc);
   1105     }
   1106 
   1107     return 2;
   1108 }
   1109 
   1110 
   1111 }; // namespace android
   1112