/* ColoredAnaglyphsShader.frag.txt
 *
 * A more complex conversion shader for color anaglyphs than the one
 * hard-wired into PTBs Screen command. Applies full 3x3 color gain
 * matrices to colors of each view channel, then adds them up, then
 * optionally applies gamma correction to the red output channel.
 *
 * Standard anaglyph conversion is implemented by the default shader in
 * Screen() and can be parameterized by SetAnaglyphStereoParameters.
 *
 * This shader is used for more complex/exotic ways of anaglyph conversion.
 *
 * Loaded/initialized and used by SetAnaglyphStereoParameters.m as part of
 * the PTB imaging pipelines color anaglyph shading support.
 *
 * (C) 2007 Mario Kleiner - Released to you under MIT license.
 */

#extension GL_ARB_texture_rectangle : enable

/* Left image channel and right image channel: */
uniform sampler2DRect Image1;
uniform sampler2DRect Image2;

/* 3 by 3 color gain matrices for left- right- channel: */
uniform mat3 GainsLeft;
uniform mat3 GainsRight;

/* Gamma value for red out channel - Set zero for no gamma correction! */
uniform float RedGamma;

void main()
{
    /* Lookup RGB pixel colors in left- and right buffer: */
    vec3 incolor1 = texture2DRect(Image1, gl_TexCoord[0].st).rgb;
    vec3 incolor2 = texture2DRect(Image2, gl_TexCoord[0].st).rgb;

    /* Multiply each vector with its corresponding xform matrix: */
    vec3 channel1 = GainsLeft  * incolor1;
    vec3 channel2 = GainsRight * incolor2;

    /* Add them up to form final output fragment RGB color: */
    gl_FragColor.rgb = channel1 + channel2;

    /* Alpha is forced to 1 - It does not matter anymore: */
    gl_FragColor.a = 1.0;

    /* Apply gamma correction to red channel, if requested: */
    /* Note: This op is expensive on GPUs without dynamic flow control! */
    if (RedGamma > 0.0) gl_FragColor.r = pow(gl_FragColor.r, RedGamma);
}