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100 lines
2.0 KiB
C++
100 lines
2.0 KiB
C++
// This code is in the public domain -- castanyo@yahoo.es
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#include <nvimage/NormalMipmap.h>
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#include <nvimage/FloatImage.h>
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#include <nvmath/Montecarlo.h>
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#include <nvmath/SphericalHarmonic.h>
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#include <nvcore/Ptr.h>
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using namespace nv;
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FloatImage * nv::createNormalMipmapMap(const FloatImage * img)
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{
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nvDebugCheck(img != NULL);
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uint w = img->width();
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uint h = img->height();
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uint hw = w / 2;
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uint hh = h / 2;
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FloatImage dotImg;
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dotImg.allocate(1, w, h);
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FloatImage shImg;
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shImg.allocate(9, hw, hh);
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SampleDistribution distribution(256);
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const uint sampleCount = distribution.sampleCount();
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for (uint d = 0; d < sampleCount; d++)
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{
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const float * xChannel = img->channel(0);
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const float * yChannel = img->channel(1);
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const float * zChannel = img->channel(2);
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Vector3 dir = distribution.sampleDir(d);
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Sh2 basis;
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basis.eval(dir);
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for(uint i = 0; i < w*h; i++)
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{
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Vector3 normal(xChannel[i], yChannel[i], zChannel[i]);
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normal = normalizeSafe(normal, Vector3(zero), 0.0f);
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dotImg.setPixel(dot(dir, normal), d);
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}
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// @@ It would be nice to have a fastDownSample that took an existing image as an argument, to avoid allocations.
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AutoPtr<FloatImage> dotMip(dotImg.fastDownSample());
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for(uint p = 0; p < hw*hh; p++)
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{
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float f = dotMip->pixel(p);
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// Project irradiance to sh basis and accumulate.
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for (uint i = 0; i < 9; i++)
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{
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float & sum = shImg.channel(i)[p];
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sum += f * basis.elemAt(i);
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}
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}
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}
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FloatImage * normalMipmap = new FloatImage;
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normalMipmap->allocate(4, hw, hh);
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// Precompute the clamped cosine radiance transfer.
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Sh2 prt;
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prt.cosineTransfer();
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// Allocate outside the loop.
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Sh2 sh;
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for(uint p = 0; p < hw*hh; p++)
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{
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for (uint i = 0; i < 9; i++)
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{
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sh.elemAt(i) = shImg.channel(i)[p];
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}
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// Convolve sh irradiance by radiance transfer.
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sh *= prt;
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// Now sh(0) is the ambient occlusion.
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// and sh(1) is the normal direction.
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// Should we use SVD to fit only the normals to the SH?
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}
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return normalMipmap;
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}
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