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// Pass-2: AA on Texture
// Note: gcv_FboTexCoord is in center of sample pixels.
vec2 texCoord = gcv_FboTexCoord.st;
float sampleCount = gcu_FboTexSize.z;
vec2 tsize = gcu_FboTexSize.xy; // tex size
vec2 psize = 1.0 / gcu_FboTexSize.xy; // pixel size
// mix(x,y,a): x*(1-a) + y*a
//
// bilinear filtering includes 2 mix:
//
// pix1 = tex[x0][y0] * ( 1 - u_ratio ) + tex[x1][y0] * u_ratio
// pix2 = tex[x0][y1] * ( 1 - u_ratio ) + tex[x1][y1] * u_ratio
// fin = pix1 * ( 1 - v_ratio ) + pix2 * v_ratio
//
// so we can use the build in mix function for these 2 computations ;-)
//
vec2 uv_ratio = fract(texCoord*tsize); // texCoord*tsize - floor(texCoord*tsize);
// Just poles (NW, SW, ..)
float pixelCount = 2 * sampleCount;
// sampleCount [0, 1, 3, 5, 7] are undefined!
float layerCount = ( sampleCount / 2.0 );
// sum of all integer [layerCount .. 1] -> Gauss
float denom = ( layerCount / 2.0 ) * ( layerCount + 1.0 );
vec4 t, p1, p2, p3, p4;
// Layer-1: SampleCount 2 -> 4x
p1 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2(-0.5, -0.5))); // NW
p2 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2(-0.5, 0.5))); // SW
p3 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2( 0.5, 0.5))); // SE
p4 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2( 0.5, -0.5))); // NE
p1 = mix( p1, p4, uv_ratio.x);
p2 = mix( p2, p3, uv_ratio.x);
t = mix ( p1, p2, uv_ratio.y );
t *= (layerCount - 0.0) / ( denom ); // weight layer 1
if( sampleCount > 2.0 ) {
// Layer-2: SampleCount 4 -> +4x = 8p
p1 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2(-1.5, -1.5))); // NW
p2 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2(-1.5, 1.5))); // SW
p3 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2( 1.5, 1.5))); // SE
p4 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2( 1.5, -1.5))); // NE
p1 = mix( p1, p4, uv_ratio.x);
p2 = mix( p2, p3, uv_ratio.x);
p3 = mix ( p1, p2, uv_ratio.y );
t += p3 * (layerCount - 1) / ( denom ); // weight layer 2
if( sampleCount > 4.0 ) {
// Layer-3: SampleCount 6 -> +4 = 12p
p1 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2(-2.5, -2.5))); // NW
p2 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2(-2.5, 2.5))); // SW
p3 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2( 2.5, 2.5))); // SE
p4 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2( 2.5, -2.5))); // NE
p1 = mix( p1, p4, uv_ratio.x);
p2 = mix( p2, p3, uv_ratio.x);
p3 = mix ( p1, p2, uv_ratio.y );
t += p3 * (layerCount - 2) / ( denom ); // weight layer 3
if( sampleCount > 6.0 ) {
// Layer-4: SampleCount 8 -> +4 = 16p
p1 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2(-3.5, -3.5))); // NW
p2 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2(-3.5, 3.5))); // SW
p3 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2( 3.5, 3.5))); // SE
p4 = texture2D(gcu_FboTexUnit, texCoord + psize*(vec2( 3.5, -3.5))); // NE
p1 = mix( p1, p4, uv_ratio.x);
p2 = mix( p2, p3, uv_ratio.x);
p3 = mix ( p1, p2, uv_ratio.y );
t += p3 * (layerCount - 3) / ( denom ); // weight layer 4
}
}
}
#if USE_DISCARD
if( 0.0 == t.w ) {
discard; // discard freezes NV tegra2 compiler
} else {
mgl_FragColor = t;
}
#else
mgl_FragColor = t;
#endif
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