96 lines
3.2 KiB
Plaintext
96 lines
3.2 KiB
Plaintext
#include "common.effect"
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// # Linear Optimization
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// While the normal way is to sample every texel in the pSize, linear optimization
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// takes advantage of the fact that most people, especially after compression,
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// will not be able to tell the difference between a linear approximation and
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// the actual thing.
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//
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// Instead of sampling every texel like this:
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//
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// |Tx|Tx|Tx|Tx|Tx|
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// Tx|-2|-1| 0|+1|+2|
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//
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// Linear optimization will sample like this:
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//
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// |Tx|Tx|Tx|Tx|Tx|
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// Tx| -1 | 0| +1 |
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//
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// This effectively removes half the necessary samples and looks identical when
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// when used with box blur. However there is an edge case when the blur width
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// is not a multiple of two, where two additional samples have to be spent on
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// reading the outer edge:
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//
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// |Tx|Tx|Tx|Tx|Tx|Tx|Tx|
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// Tx|-2| -1 | 0| +1 |+2|
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//
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// or this alternative pattern that uses two less samples:
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//
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// |Tx|Tx|Tx|Tx|Tx|Tx|Tx|
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// Tx| 0 | +1 | +2 |+3|
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//
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// or this alternative pattern that also uses two less samples:
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//
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// |Tx|Tx|Tx|Tx|Tx|Tx|Tx|
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// Tx| -2 | -1~~+1 | +2 |
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//
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// With careful planning this can even be used for other types of Blur, such as
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// Gaussian Blur, which suffers a larger hit - however there are better and
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// faster alternatives than linear sampling with Gaussian Blur, such as
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// Dual Filtering ("Dual Kawase").
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//------------------------------------------------------------------------------
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// Defines
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//------------------------------------------------------------------------------
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#define MAX_BLUR_SIZE 128
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//------------------------------------------------------------------------------
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// Technique: Directional / Area
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//------------------------------------------------------------------------------
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float4 PSBlur1D(VertexInformation vtx) : TARGET {
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float4 final = pImage.Sample(LinearClampSampler, vtx.uv) * GetKernelAt(0);
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bool is_odd = ((int(round(pSize)) % 2) == 1);
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// y = yes, s = skip, b = break
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// Size-> | 1| 2| 3| 4| 5| 6| 7|
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// -------+--+--+--+--+--+--+--+
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// n=1 | b| y| y| y| y| y| y|
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// n=2 | |bs| s| s| s| s| s|
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// n=3 | | b| b| y| y| y| y|
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// n=4 | | | |bs| s| s| s|
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// n=5 | | | | b| b| y| y|
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// n=6 | | | | | |bs| s|
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// n=7 | | | | | | b| b|
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// n=8 | | | | | | | |
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// Loop unrolling is only possible with a fixed known maximum.
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// Some compilers may unroll up to x iterations, but most will not.
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for (int n = 1; n <= MAX_BLUR_SIZE; n+=2) {
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// Different from normal box, early exit instead of late exit.
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if (n >= pSize) {
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break;
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}
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// TODO: Determine better position than 0.5 for gaussian approximation.
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float2 nstep = (pImageTexel * pStepScale) * (n + 0.5);
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float kernel = kernelAt(n) + kernelAt(n + 1);
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final += pImage.Sample(LinearClampSampler, vtx.uv + nstep) * kernel;
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final += pImage.Sample(LinearClampSampler, vtx.uv - nstep) * kernel;
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}
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if (is_odd) {
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float kernel = kernelAt(pSize);
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float2 nstep = (pImageTexel * pStepScale) * pSize;
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final += pImage.Sample(LinearClampSampler, vtx.uv + nstep) * kernel;
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final += pImage.Sample(LinearClampSampler, vtx.uv - nstep) * kernel;
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}
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return final;
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}
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technique Draw {
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pass {
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vertex_shader = VSDefault(vtx);
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pixel_shader = PSBlur1D(vtx);
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}
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}
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