1 2/* 3Copyright (c) 2019 The Khronos Group Inc. 4Use of this source code is governed by an MIT-style license that can be 5found in the LICENSE.txt file. 6*/ 7 8 9#ifdef GL_ES 10#ifdef GL_FRAGMENT_PRECISION_HIGH 11precision highp float; 12#else 13precision mediump float; 14#endif 15#endif 16varying vec4 color; 17 18void main (void) 19{ 20 const float M_PI = 3.14159265358979323846; 21 float x = 2.0 * (color.g - 0.5); 22 float y = 2.0 * (color.b - 0.5); 23 const float epsilon = 1.0e-4; 24 gl_FragColor = vec4(0.0, 0.0, 0.0, 1.0); 25 26 // Avoid evaluating atan(0, x) for x < epsilon because it's implementation-dependent 27 if(x > epsilon || abs(y) > epsilon) 28 { 29 gl_FragColor = vec4(atan(y, x) / (2.0 * M_PI) + 0.5, 0.0, 0.0, 1.0); 30 } 31} 32