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/* BlurredMipmapDemoShader.frag.txt
* Shader used for BlurredMipmapDemo.m
*
* This shader computes the level of resolution for each output texel
* during Screen('DrawTexture') of the video image texture. Resolution
* directly depends on radial distance to the provided simulated center of gaze.
*
* Resolution level is used to determine the mip-map miplevel (lod) to use for
* lookup of the mip-map filtered texel in the images mipmap pyramid.
*
* (C) 2012 Mario Kleiner - Licensed under MIT license.
*
*/
#extension GL_ARB_shader_texture_lod : enable
/* Image is the mip-mapped texture with the image resolution pyramid: */
uniform sampler2D Image;
/* Passed from vertex shader: */
varying vec4 baseColor;
varying vec2 gazePosition;
varying float gazeRadius;
void main(void)
{
/* Output pixel position in absolute window coordinates: */
vec2 outpos = gl_FragCoord.xy;
/* Compute distance to center of gaze, normalized to units of gazeRadius: */
/* We take log2 of it, because lod selects mip-level, which selects for a */
/* 2^lod decrease in resolution: */
float lod = log2(distance(outpos, gazePosition) / gazeRadius);
/* Lookup texel color in image pyramid at input texture coordinate and
* specific mip-map level 'lod': */
vec4 texel = texture2DLod(Image, gl_TexCoord[0].st, lod);
/* Apply modulation baseColor and write to framebuffer: */
gl_FragColor = texel * baseColor;
}
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