Index: conformance/ogles/GL/cos/cos_float_frag_xvary_ref.frag |
=================================================================== |
--- conformance/ogles/GL/cos/cos_float_frag_xvary_ref.frag (revision 0) |
+++ conformance/ogles/GL/cos/cos_float_frag_xvary_ref.frag (working copy) |
@@ -0,0 +1,70 @@ |
+ |
+/* |
+** 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. |
+*/ |
+ |
+ |
+#ifdef GL_ES |
+precision mediump float; |
+#endif |
+varying vec4 color; |
+ |
+void main (void) |
+{ |
+ const float M_PI = 3.14159265358979323846; |
+ float c = 2.0 * M_PI * ( fract(abs(color.r)) - 0.5 ); |
+ float sign = 1.0; |
+ float cos_c = -1.0; |
+ float fact_even = 1.0; |
+ float fact_odd = 1.0; |
+ float sum; |
+ |
+ // 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); |
+ |
+ // pow(c, float(i/2)) 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), float(i/2))/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), float(i/2))*(sum/fact_odd); |
+ |
+ sign = -sign; |
+ } |
+ |
+ gl_FragColor = vec4(0.5 * cos_c + 0.5, 0.0, 0.0, 1.0); |
+} |