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/*
* File: SquareWaveApertureShader.frag.txt
* Shader for drawing of basic parameterized square wave grating patches.
* Applies a circular aperture of radius 'Radius'.
*
* Copyright 2011, Ian Andolina <http://github.com/iandol>, licenced under the MIT Licence
*
*/
uniform float Radius;
uniform vec2 Center;
uniform vec4 Offset;
float Dist;
varying vec4 baseColor;
varying float Phase;
varying float FreqTwoPi;
void main()
{
/* Query current output texel position: */
vec2 pos = gl_TexCoord[0].xy;
/* find our distance from center */
Dist = distance(pos, Center);
/* If distance to center (aka radius of pixel) > Radius, discard this pixel: */
if (Dist > Radius) discard;
/* Evaluate sine grating at requested position, frequency and phase: */
float sv = sin(pos.x * FreqTwoPi + Phase);
sv = smoothstep(-0.2, 0.2, sv) * 2.0 - 1.0;
/* Multiply/Modulate base color and alpha with calculated sine */
/* values, add some constant color/alpha Offset, assign as final fragment */
/* output color: */
gl_FragColor = (baseColor * sv) + Offset;
gl_FragColor.a = sv;
}
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