| |
| /* |
| ** 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; |
| vec2 x = 2.0 * (gtf_Color.gg - 0.5); |
| vec2 y = 2.0 * (gtf_Color.bb - 0.5); |
| vec2 c; |
| vec2 atan_c = vec2(0.0); |
| vec2 scale = vec2(1.0); |
| vec2 sign = vec2(1.0); |
| vec4 result = vec4(0.0, 0.0, 0.0, 1.0); |
| const float epsilon = 1.0e-4; |
| |
| // Avoid evaluating atan(0, x) for x < epsilon because it's implementation-dependent |
| if(x[0] > epsilon || abs(y[0]) > epsilon) |
| { |
| if(x[0] < 0.0 ^^ y[0] < 0.0) |
| { |
| sign[0] = -1.0; |
| } |
| |
| if(abs(y[0]) <= abs(x[0])) |
| { |
| c[0] = abs(y[0] / x[0]); |
| // Taylors series expansion for atan |
| atan_c[0] += scale[0] * pow(c[0], float(1)) / float(1); |
| scale[0] *= -1.0; |
| atan_c[0] += scale[0] * pow(c[0], float(3)) / float(3); |
| scale[0] *= -1.0; |
| atan_c[0] += scale[0] * pow(c[0], float(5)) / float(5); |
| scale[0] *= -1.0; |
| atan_c[0] += scale[0] * pow(c[0], float(7)) / float(7); |
| scale[0] *= -1.0; |
| atan_c[0] += scale[0] * pow(c[0], float(9)) / float(9); |
| scale[0] *= -1.0; |
| atan_c[0] += scale[0] * pow(c[0], float(11)) / float(11); |
| scale[0] *= -1.0; |
| |
| result[0] = sign[0] * atan_c[0] / (2.0 * M_PI) + 0.5; |
| } |
| else |
| { |
| c[0] = abs(x[0] / y[0]); |
| |
| // Taylors series expansion for atan |
| atan_c[0] += scale[0] * pow(c[0], float(1)) / float(1); |
| scale[0] *= -1.0; |
| atan_c[0] += scale[0] * pow(c[0], float(3)) / float(3); |
| scale[0] *= -1.0; |
| atan_c[0] += scale[0] * pow(c[0], float(5)) / float(5); |
| scale[0] *= -1.0; |
| atan_c[0] += scale[0] * pow(c[0], float(7)) / float(7); |
| scale[0] *= -1.0; |
| atan_c[0] += scale[0] * pow(c[0], float(9)) / float(9); |
| scale[0] *= -1.0; |
| atan_c[0] += scale[0] * pow(c[0], float(11)) / float(11); |
| scale[0] *= -1.0; |
| |
| result[0] = sign[0] * (M_PI / 2.0 - atan_c[0]) / (2.0 * M_PI) + 0.5; |
| } |
| |
| if(x[0] < 0.0) |
| if(y[0] < 0.0) result[0] -= 0.5; |
| else if(y[0] > 0.0) result[0] += 0.5; |
| } |
| |
| if(x[1] > epsilon || abs(y[1]) > epsilon) |
| { |
| if(x[1] < 0.0 ^^ y[1] < 0.0) |
| { |
| sign[1] = -1.0; |
| } |
| |
| if(abs(y[1]) <= abs(x[1])) |
| { |
| c[1] = abs(y[1] / x[1]); |
| // Taylors series expansion for atan |
| atan_c[1] += scale[1] * pow(c[1], float(1)) / float(1); |
| scale[1] *= -1.0; |
| atan_c[1] += scale[1] * pow(c[1], float(3)) / float(3); |
| scale[1] *= -1.0; |
| atan_c[1] += scale[1] * pow(c[1], float(5)) / float(5); |
| scale[1] *= -1.0; |
| atan_c[1] += scale[1] * pow(c[1], float(7)) / float(7); |
| scale[1] *= -1.0; |
| atan_c[1] += scale[1] * pow(c[1], float(9)) / float(9); |
| scale[1] *= -1.0; |
| atan_c[1] += scale[1] * pow(c[1], float(11)) / float(11); |
| scale[1] *= -1.0; |
| |
| result[1] = sign[1] * atan_c[1] / (2.0 * M_PI) + 0.5; |
| } |
| else |
| { |
| c[1] = abs(x[1] / y[1]); |
| |
| // Taylors series expansion for atan |
| atan_c[1] += scale[1] * pow(c[1], float(1)) / float(1); |
| scale[1] *= -1.0; |
| atan_c[1] += scale[1] * pow(c[1], float(3)) / float(3); |
| scale[1] *= -1.0; |
| atan_c[1] += scale[1] * pow(c[1], float(5)) / float(5); |
| scale[1] *= -1.0; |
| atan_c[1] += scale[1] * pow(c[1], float(7)) / float(7); |
| scale[1] *= -1.0; |
| atan_c[1] += scale[1] * pow(c[1], float(9)) / float(9); |
| scale[1] *= -1.0; |
| atan_c[1] += scale[1] * pow(c[1], float(11)) / float(11); |
| scale[1] *= -1.0; |
| |
| result[1] = sign[1] * (M_PI / 2.0 - atan_c[1]) / (2.0 * M_PI) + 0.5; |
| } |
| |
| if(x[1] < 0.0) |
| if(y[1] < 0.0) result[1] -= 0.5; |
| else if(y[1] > 0.0) result[1] += 0.5; |
| } |
| |
| color = result; |
| gl_Position = gtf_ModelViewProjectionMatrix * gtf_Vertex; |
| } |