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      1 
      2 /*
      3  * Copyright (C) 2013 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 #ifndef ANDROID_HWUI_SHADOW_TESSELLATOR_H
     19 #define ANDROID_HWUI_SHADOW_TESSELLATOR_H
     20 
     21 #include <SkPath.h>
     22 
     23 #include "Debug.h"
     24 #include "Matrix.h"
     25 
     26 namespace android {
     27 namespace uirenderer {
     28 
     29 class VertexBuffer;
     30 
     31 // All SHADOW_* are used to define all the geometry property of shadows.
     32 // Use a simplified example to illustrate the geometry setup here.
     33 // Assuming we use 6 rays and only 1 layer, Then we will have 2 hexagons, which
     34 // are 0 to 5 and 6 to 11. The area between them will be the penumbra area, and
     35 // the area inside the 2nd hexagon is the umbra.
     36 // Ambient shadow is using only 1 layer for opaque caster, otherwise, spot
     37 // shadow and ambient shadow are using 2 layers.
     38 // Triange strip indices for penumbra area: (0, 6, 1, 7, 2, 8, 3, 9, 4, 10, 5, 11, 0, 6)
     39 //                 0
     40 //
     41 //      5          6         1
     42 //           11         7
     43 //
     44 //           10         8
     45 //      4          9         2
     46 //
     47 //                 3
     48 
     49 // The total number of rays starting from the centroid of shadow area, in order
     50 // to generate the shadow geometry.
     51 #define SHADOW_RAY_COUNT 128
     52 
     53 // The total number of all the vertices representing the shadow.
     54 // For the case we only have 1 layer, then we will just fill only 2/3 of it.
     55 #define SHADOW_VERTEX_COUNT (3 * SHADOW_RAY_COUNT)
     56 
     57 // The total number of indices used for drawing the shadow geometry as triangle strips.
     58 // Depending on the mode we are drawing, we can have 1 layer or 2 layers.
     59 // Therefore, we only build the longer index buffer.
     60 #define TWO_POLY_RING_SHADOW_INDEX_COUNT (4 * (SHADOW_RAY_COUNT + 1))
     61 #define ONE_POLY_RING_SHADOW_INDEX_COUNT (2 * (SHADOW_RAY_COUNT + 1))
     62 
     63 #define MAX_SHADOW_INDEX_COUNT TWO_POLY_RING_SHADOW_INDEX_COUNT
     64 
     65 #define SHADOW_MIN_CASTER_Z 0.001f
     66 
     67 #define MINIMAL_DELTA_THETA (M_PI / 180 / 1000)
     68 
     69 class ShadowTessellator {
     70 public:
     71     static void tessellateAmbientShadow(bool isCasterOpaque,
     72             const Vector3* casterPolygon, int casterVertexCount,
     73             const Vector3& centroid3d,  const Rect& casterBounds,
     74             const Rect& localClip, float maxZ, VertexBuffer& shadowVertexBuffer);
     75 
     76     static void tessellateSpotShadow(bool isCasterOpaque,
     77             const Vector3* casterPolygon, int casterVertexCount, const Vector3& casterCentroid,
     78             const mat4& receiverTransform, const Vector3& lightCenter, int lightRadius,
     79             const Rect& casterBounds, const Rect& localClip, VertexBuffer& shadowVertexBuffer);
     80 
     81     static Vector2 centroid2d(const Vector2* poly, int polyLength);
     82 
     83     static Vector2 calculateNormal(const Vector2& p1, const Vector2& p2);
     84 
     85     static int getExtraVertexNumber(const Vector2& vector1, const Vector2& vector2,
     86             float divisor);
     87 
     88     static void checkOverflow(int used, int total, const char* bufferName);
     89 }; // ShadowTessellator
     90 
     91 }; // namespace uirenderer
     92 }; // namespace android
     93 
     94 #endif // ANDROID_HWUI_SHADOW_TESSELLATOR_H
     95