| |
| /* |
| ** Copyright (c) 2012 The Khronos Group Inc. |
| ** |
| ** Permission is hereby granted, free of charge, to any person obtaining a |
| ** copy of this software and/or associated documentation files (the |
| ** "Materials"), to deal in the Materials without restriction, including |
| ** without limitation the rights to use, copy, modify, merge, publish, |
| ** distribute, sublicense, and/or sell copies of the Materials, and to |
| ** permit persons to whom the Materials are furnished to do so, subject to |
| ** the following conditions: |
| ** |
| ** The above copyright notice and this permission notice shall be included |
| ** in all copies or substantial portions of the Materials. |
| ** |
| ** THE MATERIALS ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
| ** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
| ** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. |
| ** IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY |
| ** CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, |
| ** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE |
| ** MATERIALS OR THE USE OR OTHER DEALINGS IN THE MATERIALS. |
| */ |
| |
| |
| attribute vec4 gtf_Vertex; |
| attribute vec4 gtf_Color; |
| uniform mat4 gtf_ModelViewProjectionMatrix; |
| varying vec4 color; |
| |
| void main (void) |
| { |
| const float M_PI = 3.14159265358979323846; |
| float c = 2.0 * (gtf_Color.r - 0.5); |
| |
| float asin_c = 0.0; |
| float scale = 1.0; |
| float sign = 1.0; |
| |
| // pow can't handle negative numbers so take advantage of symmetry |
| if(c < 0.0) |
| { |
| sign = -1.0; |
| c *= -1.0; |
| } |
| |
| // Taylors series expansion for asin |
| // 1000/2 iterations necessary to get the accuracy with this method |
| for(int i = 1; i < 1000; i += 2) |
| { |
| asin_c += scale * pow(c, float(i)) / float(i); |
| scale *= float(i) / float(i + 1); |
| } |
| |
| color = vec4(sign * asin_c / M_PI + 0.5, 0.0, 0.0, 1.0); |
| gl_Position = gtf_ModelViewProjectionMatrix * gtf_Vertex; |
| } |