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Diffstat (limited to '')
| -rw-r--r-- | dom/canvas/test/webgl-conf/checkout/conformance/ogles/GL/cos/cos_vec2_frag_xvary_ref.frag | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/ogles/GL/cos/cos_vec2_frag_xvary_ref.frag b/dom/canvas/test/webgl-conf/checkout/conformance/ogles/GL/cos/cos_vec2_frag_xvary_ref.frag new file mode 100644 index 0000000000..ad44ee73f2 --- /dev/null +++ b/dom/canvas/test/webgl-conf/checkout/conformance/ogles/GL/cos/cos_vec2_frag_xvary_ref.frag @@ -0,0 +1,57 @@ + +/* +Copyright (c) 2019 The Khronos Group Inc. +Use of this source code is governed by an MIT-style license that can be +found in the LICENSE.txt file. +*/ + + +#ifdef GL_ES +precision mediump float; +#endif +varying vec4 color; + +void main (void) +{ + const float M_PI = 3.14159265358979323846; + vec2 c = 2.0 * M_PI * ( fract(abs(color.rg)) - 0.5 ); + float sign = 1.0; + vec2 cos_c = vec2(-1.0, -1.0); + float fact_even = 1.0; + float fact_odd = 1.0; + vec2 sum; + vec2 exp; + + // At this point c is in the range [-PI, PI) + + // Taylor-Maclaurin series expansion for cosine + // + // Apply the property that pow(a, b + c) = pow(a, b) * pow(a, c) + // and the property that 1.0/(a*b) = 1.0/a * 1.0/b + // to make sure no register ever overflows the range (-16384, +16384) + // mandated for mediump variables. + + for(int i = 2; i <= 10; i += 2) + { + // fact_even will hold at most the value 3840. + fact_even *= float(i); + + // fact_odd will always be smaller than fact_even + fact_odd *= float(i-1); + + // exp is at most (5,5) + exp = vec2(float(i/2), float(i/2)); + + // pow(c, exp) takes at most the value pow(PI, 5), which is approx. 306 + // abs(sum) is at most PI/2.0 + sum = sign * pow(abs(c), exp)/fact_even; + + // abs(sum/fact_odd) is at most PI/2.0 + // cos_c is always bound in the range [-1.0, 1.0) + cos_c += pow(abs(c), exp)*(sum/fact_odd); + + sign = -sign; + } + + gl_FragColor = vec4(0.5 * cos_c + 0.5, 0.0, 1.0); +} |