Add ToT WebGL conformance tests : part 9

conformance/ogles/GL/cos/cos_vec2_frag_xvary_ref.frag

Index: conformance/ogles/GL/cos/cos_vec2_frag_xvary_ref.frag
===================================================================
--- conformance/ogles/GL/cos/cos_vec2_frag_xvary_ref.frag	(revision 0)
+++ conformance/ogles/GL/cos/cos_vec2_frag_xvary_ref.frag	(working copy)
@@ -0,0 +1,74 @@
+
+/*
+** 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;
+	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);
+}