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 vec3 x = 2.0 * (gtf_Color.ggg - 0.5); 18 vec3 y = 2.0 * (gtf_Color.bbb - 0.5); 19 vec3 c; 20 vec3 atan_c = vec3(0.0); 21 vec3 scale = vec3(1.0); 22 vec3 sign = vec3(1.0); 23 vec4 result = vec4(0.0, 0.0, 0.0, 1.0); 24 const float epsilon = 1.0e-4; 25 26 // Avoid evaluating atan(0, x) for x < epsilon because it's implementation-dependent 27 if(x[0] > epsilon || abs(y[0]) > epsilon) 28 { 29 if(x[0] < 0.0 ^^ y[0] < 0.0) 30 { 31 sign[0] = -1.0; 32 } 33 34 if(abs(y[0]) <= abs(x[0])) 35 { 36 c[0] = abs(y[0] / x[0]); 37 // Taylors series expansion for atan 38 atan_c[0] += scale[0] * pow(c[0], float(1)) / float(1); 39 scale[0] *= -1.0; 40 atan_c[0] += scale[0] * pow(c[0], float(3)) / float(3); 41 scale[0] *= -1.0; 42 atan_c[0] += scale[0] * pow(c[0], float(5)) / float(5); 43 scale[0] *= -1.0; 44 atan_c[0] += scale[0] * pow(c[0], float(7)) / float(7); 45 scale[0] *= -1.0; 46 atan_c[0] += scale[0] * pow(c[0], float(9)) / float(9); 47 scale[0] *= -1.0; 48 atan_c[0] += scale[0] * pow(c[0], float(11)) / float(11); 49 scale[0] *= -1.0; 50 51 result[0] = sign[0] * atan_c[0] / (2.0 * M_PI) + 0.5; 52 } 53 else 54 { 55 c[0] = abs(x[0] / y[0]); 56 57 // Taylors series expansion for atan 58 atan_c[0] += scale[0] * pow(c[0], float(1)) / float(1); 59 scale[0] *= -1.0; 60 atan_c[0] += scale[0] * pow(c[0], float(3)) / float(3); 61 scale[0] *= -1.0; 62 atan_c[0] += scale[0] * pow(c[0], float(5)) / float(5); 63 scale[0] *= -1.0; 64 atan_c[0] += scale[0] * pow(c[0], float(7)) / float(7); 65 scale[0] *= -1.0; 66 atan_c[0] += scale[0] * pow(c[0], float(9)) / float(9); 67 scale[0] *= -1.0; 68 atan_c[0] += scale[0] * pow(c[0], float(11)) / float(11); 69 scale[0] *= -1.0; 70 71 result[0] = sign[0] * (M_PI / 2.0 - atan_c[0]) / (2.0 * M_PI) + 0.5; 72 } 73 74 if(x[0] < 0.0) 75 if(y[0] < 0.0) result[0] -= 0.5; 76 else if(y[0] > 0.0) result[0] += 0.5; 77 } 78 79 if(x[1] > epsilon || abs(y[1]) > epsilon) 80 { 81 if(x[1] < 0.0 ^^ y[1] < 0.0) 82 { 83 sign[1] = -1.0; 84 } 85 86 if(abs(y[1]) <= abs(x[1])) 87 { 88 c[1] = abs(y[1] / x[1]); 89 // Taylors series expansion for atan 90 atan_c[1] += scale[1] * pow(c[1], float(1)) / float(1); 91 scale[1] *= -1.0; 92 atan_c[1] += scale[1] * pow(c[1], float(3)) / float(3); 93 scale[1] *= -1.0; 94 atan_c[1] += scale[1] * pow(c[1], float(5)) / float(5); 95 scale[1] *= -1.0; 96 atan_c[1] += scale[1] * pow(c[1], float(7)) / float(7); 97 scale[1] *= -1.0; 98 atan_c[1] += scale[1] * pow(c[1], float(9)) / float(9); 99 scale[1] *= -1.0; 100 atan_c[1] += scale[1] * pow(c[1], float(11)) / float(11); 101 scale[1] *= -1.0; 102 103 result[1] = sign[1] * atan_c[1] / (2.0 * M_PI) + 0.5; 104 } 105 else 106 { 107 c[1] = abs(x[1] / y[1]); 108 109 // Taylors series expansion for atan 110 atan_c[1] += scale[1] * pow(c[1], float(1)) / float(1); 111 scale[1] *= -1.0; 112 atan_c[1] += scale[1] * pow(c[1], float(3)) / float(3); 113 scale[1] *= -1.0; 114 atan_c[1] += scale[1] * pow(c[1], float(5)) / float(5); 115 scale[1] *= -1.0; 116 atan_c[1] += scale[1] * pow(c[1], float(7)) / float(7); 117 scale[1] *= -1.0; 118 atan_c[1] += scale[1] * pow(c[1], float(9)) / float(9); 119 scale[1] *= -1.0; 120 atan_c[1] += scale[1] * pow(c[1], float(11)) / float(11); 121 scale[1] *= -1.0; 122 123 result[1] = sign[1] * (M_PI / 2.0 - atan_c[1]) / (2.0 * M_PI) + 0.5; 124 } 125 126 if(x[1] < 0.0) 127 if(y[1] < 0.0) result[1] -= 0.5; 128 else if(y[1] > 0.0) result[1] += 0.5; 129 } 130 131 if(x[2] > epsilon || abs(y[2]) > epsilon) 132 { 133 if(x[2] < 0.0 ^^ y[2] < 0.0) 134 { 135 sign[2] = -1.0; 136 } 137 138 if(abs(y[2]) <= abs(x[2])) 139 { 140 c[2] = abs(y[2] / x[2]); 141 // Taylors series expansion for atan 142 atan_c[2] += scale[2] * pow(c[2], float(1)) / float(1); 143 scale[2] *= -1.0; 144 atan_c[2] += scale[2] * pow(c[2], float(3)) / float(3); 145 scale[2] *= -1.0; 146 atan_c[2] += scale[2] * pow(c[2], float(5)) / float(5); 147 scale[2] *= -1.0; 148 atan_c[2] += scale[2] * pow(c[2], float(7)) / float(7); 149 scale[2] *= -1.0; 150 atan_c[2] += scale[2] * pow(c[2], float(9)) / float(9); 151 scale[2] *= -1.0; 152 atan_c[2] += scale[2] * pow(c[2], float(11)) / float(11); 153 scale[2] *= -1.0; 154 155 result[2] = sign[2] * atan_c[2] / (2.0 * M_PI) + 0.5; 156 } 157 else 158 { 159 c[2] = abs(x[2] / y[2]); 160 161 // Taylors series expansion for atan 162 atan_c[2] += scale[2] * pow(c[2], float(1)) / float(1); 163 scale[2] *= -1.0; 164 atan_c[2] += scale[2] * pow(c[2], float(3)) / float(3); 165 scale[2] *= -1.0; 166 atan_c[2] += scale[2] * pow(c[2], float(5)) / float(5); 167 scale[2] *= -1.0; 168 atan_c[2] += scale[2] * pow(c[2], float(7)) / float(7); 169 scale[2] *= -1.0; 170 atan_c[2] += scale[2] * pow(c[2], float(9)) / float(9); 171 scale[2] *= -1.0; 172 atan_c[2] += scale[2] * pow(c[2], float(11)) / float(11); 173 scale[2] *= -1.0; 174 175 result[2] = sign[2] * (M_PI / 2.0 - atan_c[2]) / (2.0 * M_PI) + 0.5; 176 } 177 178 if(x[2] < 0.0) 179 if(y[2] < 0.0) result[2] -= 0.5; 180 else if(y[2] > 0.0) result[2] += 0.5; 181 } 182 183 color = result; 184 gl_Position = gtf_ModelViewProjectionMatrix * gtf_Vertex; 185} 186