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 9attribute vec4 gtf_Vertex; 10attribute vec4 gtf_Color; 11uniform mat4 gtf_ModelViewProjectionMatrix; 12varying vec4 color; 13 14void main (void) 15{ 16 const float M_PI = 3.14159265358979323846; 17 float x = 2.0 * (gtf_Color.g - 0.5); 18 float y = 2.0 * (gtf_Color.b - 0.5); 19 const float epsilon = 1.0e-4; 20 color = vec4(0.0, 0.0, 0.0, 1.0); 21 22 // Avoid evaluating atan(0, x) for x < epsilon because it's implementation-dependent 23 if(x > epsilon || abs(y) > epsilon) 24 { 25 color = vec4(atan(y, x) / (2.0 * M_PI) + 0.5, 0.0, 0.0, 1.0); 26 } 27 28 gl_Position = gtf_ModelViewProjectionMatrix * gtf_Vertex; 29} 30