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#extension GL_ARB_texture_rectangle : enable
uniform sampler2DRect currentFrame, previousFrame;
uniform float lambda;
uniform vec2 scale;
vec2 offset = vec2(1.,1.);
vec2 texcoord0 = gl_TexCoord[0].st;
vec2 texcoord1 = gl_TexCoord[1].st;
void main()
{
vec4 a = texture2DRect(currentFrame, texcoord0);
vec4 b = texture2DRect(previousFrame , texcoord1);
vec2 x1 = vec2(offset.x,0.);
vec2 y1 = vec2(0.,offset.y);
//get the difference
vec4 curdif = b-a;
//calculate the gradient
vec4 gradx = texture2DRect(previousFrame, texcoord1+x1)-texture2DRect(previousFrame, texcoord1-x1);
gradx += texture2DRect(currentFrame, texcoord0+x1)-texture2DRect(currentFrame, texcoord0-x1);
vec4 grady = texture2DRect(previousFrame, texcoord1+y1)-texture2DRect(previousFrame, texcoord1-y1);
grady += texture2DRect(currentFrame, texcoord0+y1)-texture2DRect(currentFrame, texcoord0-y1);
vec4 gradmag = sqrt((gradx*gradx)+(grady*grady)+vec4(lambda));
if ( gradmag.r == 0. ) {
gl_FragColor = vec4(0.5,0.5,0.5,1);
return;
}
vec4 vx = curdif*(gradx/gradmag);
float vxd = vx.r;//assumes greyscale
//format output for flowrepos, out(-x,+x,-y,+y)
//~ vec2 xout = vec2(max(vxd,0.),abs(min(vxd,0.)))*scale.x;
float xout = ((vxd/2.)*scale.x+0.5);
vec4 vy = curdif*(grady/gradmag);
float vyd = vy.r;//assumes greyscale
//format output for flowrepos, out(-x,+x,-y,+y)
//~ vec2 yout = vec2(max(vyd,0.),abs(min(vyd,0.)))*scale.y;
float yout = ((vyd/2.)*scale.y+0.5);
//~ gl_FragColor = vec4(xout.xy,yout.xy);
gl_FragColor = vec4(xout,yout,0.5,1.);
}
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