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/*
* File: SeparateAlphaTextureShader.frag.txt
* Shader for drawing of textures where the alpha channel is looked up
* separately from the RGB channels, i.e. RGB texel lookup uses texture
* coordinates offset by given optional shift parameters.
*
* (c) 2009 by Mario Kleiner, licensed under MIT license.
*
*/
#extension GL_ARB_texture_rectangle : enable
uniform sampler2DRect Image;
uniform vec4 Offset;
varying vec4 baseColor;
void main()
{
/* Read alpha channel value from standard texture coordinate set: */
float alpha = texture2DRect(Image, gl_TexCoord[0].st).a;
/* Read RGB color values from secondary texture coordinate set: */
vec3 rgb = texture2DRect(Image, gl_TexCoord[1].st).rgb;
/* Assemble back into RGBA quadruple: */
vec4 rgba = vec4(rgb, alpha);
/* ... and output to framebuffer, with proper modulation and offset applied: */
gl_FragColor = (baseColor * rgba) + Offset;
}
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