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/* FDF shader for sampling of tracked object surface at provided sampling
* positions from sample distribution in order to update foreground dot
* position distribution.
*
* (c) 2008 by Mario Kleiner, licensed under MIT license.
*/
#extension GL_ARB_texture_rectangle : enable
uniform sampler2DRect SampleBuffer;
uniform sampler2DRect GeometryBuffer;
uniform sampler2DRect Silhouette;
uniform float zThreshold;
uniform float ViewportHeight;
uniform vec2 texWrapAround;
uniform vec4 TextureOffsetBias;
uniform vec4 clipVertex;
void main(void)
{
/* Read sample definition from SampleBuffer: */
vec3 sample = texture2DRect(SampleBuffer, gl_TexCoord[0].st).rgb;
/* Valid sample, ie. blue channel greater zero? */
if (sample.b > 0.0) {
/* Valid sample: Readout (x,y) position from trackbuffer: */
/* Use bilinear filtering to reduce aliasing artifacts: */
vec2 texinpos = sample.rg;
vec4 tl=texture2DRect(GeometryBuffer, mod(floor(texinpos), texWrapAround));
vec4 tr=texture2DRect(GeometryBuffer, mod(floor(texinpos) + vec2(1.0, 0.0), texWrapAround));
vec4 bl=texture2DRect(GeometryBuffer, mod(floor(texinpos) + vec2(0.0, 1.0), texWrapAround));
vec4 br=texture2DRect(GeometryBuffer, mod(floor(texinpos) + vec2(1.0, 1.0), texWrapAround));
/* Perform weighted linear interpolation -- bilinear interpolation of the 4: */
tl=mix(tl,tr,fract(texinpos.x));
bl=mix(bl,br,fract(texinpos.x));
vec4 position = mix(tl, bl, fract(texinpos.y));
/* Potential zpos from GeometryBuffer: */
float zpos = position.b;
/* Reference zdepth from Silhouette: */
float refz = texture2DRect(Silhouette, position.xy).a;
/* Check for occlusion - Discard this vertex if z-values do not match aka occluded: */
if (abs(zpos - refz) > zThreshold) {
/* Discard this hidden vertex: Set it to a position that will get clipped away: */
gl_FragColor = clipVertex;
}
else {
/* Return dot (x,y) image plane position in R and G channels: */
gl_FragColor.rg = vec2(position.x, ViewportHeight - position.y);
/* Set (z,w) components (aka (b,a)) to remapped 'texinpos' texture coordinates of sample: */
gl_FragColor.ba = (texinpos * TextureOffsetBias.zw) + TextureOffsetBias.xy;
}
}
else {
/* Dead/Invalid sample: Writeout a null vertex which will */
/* get clipped away during rendering: */
gl_FragColor = clipVertex;
}
}
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