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      1 /*
      2  * Copyright (C) 2015 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #pragma version(1)
     18 #pragma rs java_package_name(com.example.android.rs.vr.engine)
     19 #pragma rs_fp_relaxed
     20 
     21 int size;
     22 int z;
     23 rs_allocation volume;
     24 
     25 /* Unused function:
     26 static float3 nylander(float3 p, int n) {
     27     float3 out;
     28     float r = length(p);
     29     float phi = atan2(p.y, p.x);
     30     float theta = acos(p.z / r);
     31     float rn = pow(r, n);
     32     out.x = sin(n * theta) * cos(n * phi);
     33     out.y = sin(n * theta) * sin(n * phi);
     34     out.z = cos(n * theta);
     35     return out * rn;
     36 }
     37 */
     38 
     39 /**
     40 * 8 x faster than the above for n = 3
     41 */
     42 static float3 nylander3(float3 p) {
     43     float3 out = (float3){0.f, 0.f, 0.f};
     44     float xy2 = p.x * p.x + p.y * p.y;
     45     if (xy2 == 0) return out;
     46     float z23x2y2 = (3 * p.z * p.z - p.x * p.x - p.y * p.y);
     47     out.x = (z23x2y2 * p.x * (p.x * p.x - 3 * p.y * p.y)) / xy2;
     48     out.y = (z23x2y2 * p.y * (3 * p.x * p.x - p.y * p.y)) / xy2;
     49     out.z = p.z * (p.z * p.z - 3 * p.x * p.x - 3 * p.y * p.y);
     50     return out;
     51 }
     52 
     53 short __attribute__((kernel)) mandelbulb(uint32_t x, uint32_t y) {
     54     int size2 = size / 2;
     55      if (z < size2) {
     56           return 256-4*(size2-z+4)*hypot((float)x-size2,(float)y-size2) / size2 ;
     57     }
     58     float3 c = (float3) {(float) x, (float) y, (float) z};
     59     c = ((c - size2) / (size2 * .9f));
     60 
     61     int loop = 25;
     62     float3 p = c;
     63     float len;
     64     for (int i = 0; i < loop; i++) {
     65         //    p = nylander(p, 3) + c;
     66         p = nylander3(p) + c;
     67         len = fast_length(p);
     68         if (len > 2.f) return 255 - loop*10;
     69         if (len < .3f) return loop*10;
     70 
     71     }
     72     len = length(p);
     73     return (short) (255 - (len * 255) / 4);
     74 }
     75 
     76 void __attribute__((kernel)) copy(short in, uint32_t x, uint32_t y) {
     77     rsSetElementAt_short(volume, in, x, y, z);
     78 }
     79