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/*
* File: ColorGratingShader.frag.txt
* Shader for drawing of color gratings.
*
* Copyright 2014, Ian Andolina <http://github.com/iandol>, licenced under the MIT Licence
*
*/
uniform vec2 center;
uniform vec4 color1;
uniform vec4 color2;
uniform float radius;
varying vec3 baseColor;
varying float alpha;
varying float phase;
varying float frequency;
varying float sigma;
varying float contrast;
void main() {
//current position
vec2 pos = gl_TexCoord[0].xy;
/* find our distance from center, if distance to center (aka radius of pixel) > Radius, discard this pixel: */
if ( radius > 0.0 ) {
float dist = distance( pos, center );
if ( dist > radius ) discard;
}
//create our sinusoid in -1 to 1 range
float sv = sin( pos.x * frequency + phase );
//if sigma >= 0, we want a squarewave grating, step or smoothstep does this depending on sigma value
if ( sigma == 0.0 ) {
sv = step( sigma, sv ); //converts into 0-1 range
}
else if ( sigma > 0.0 ) {
sv = smoothstep( -sigma, sigma, sv ); //converts into 0-1 range
}
else {
sv = ( sv + 1.0 ) / 2.0; //simply get sv into 0 - 1 range (preserving sinusoid);
}
vec3 colorA = color1.rgb;
vec3 colorB = color2.rgb;
//blend our colours from the base colour if contrast < 1
if ( contrast < 1.0 ) {
colorA = mix( baseColor, color1.rgb, contrast );
colorB = mix( baseColor, color2.rgb, contrast );
}
// and then mix the two colors using sv (our position in the grating)
vec3 colorOut = mix(colorA, colorB, sv);
// off to the display, byebye little pixel!
gl_FragColor = vec4( colorOut, alpha );
}
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