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/*
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.
*/
attribute vec4 gtf_Color;
attribute vec4 gtf_Vertex;
uniform mat4 gtf_ModelViewProjectionMatrix;
varying vec4 color;
const float ln2 = 0.69314718055994530941723212145818;
void main (void)
{
vec2 x = 31.0 * gtf_Color.rg + 1.0;
vec2 y = vec2(0.0);
vec2 z; // x-1 / x+1
int n = 50;
// ln(x) = 2[x-1 + 1 (x-1)^3 + 1 (x-1)^5 + ...] for x > 0
// [x+1 3 (x+1) 5 (x+1) ]
z = (x - 1.0) / (x + 1.0);
vec2 p = z;
for(int i = 1; i <= 101; i += 2)
{
y += p / float(i);
p *= z * z;
}
y *= 2.0 / ln2;
color = vec4(y / 5.0, 0.0, 1.0);
gl_Position = gtf_ModelViewProjectionMatrix * gtf_Vertex;
}
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