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Improved GGX cubemap filter.

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This commit is contained in:
Branimir Karadžić
2018-07-13 18:02:48 -07:00
parent 4c809cb2b2
commit ef8639ca40
1 changed files with 98 additions and 29 deletions
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127
src/image_cubemap_filter.cpp
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@@ -663,10 +663,17 @@ namespace bimg
struct Sampler
{
Sampler(const ImageContainer& _image, uint16_t _side, float _lod)
Sampler(const ImageContainer& _image, uint16_t _side, float _lod, float (*func)(float) )
{
const uint8_t lod = uint8_t(bx::clamp(_lod, 0.0f, 1.0f) * _image.m_numMips);
imageGetRawData(_image, _side, lod, _image.m_data, _image.m_size, mip);
const float lod = bx::clamp(_lod, 0.0f, 1.0f) * (_image.m_numMips - 1);
imageGetRawData(
_image
, _side
, uint8_t(func(lod) )
, _image.m_data
, _image.m_size
, mip
);
}
ImageMip mip;
@@ -688,34 +695,70 @@ namespace bimg
uint8_t side;
dirToTexelUv(uu, vv, side, _dir);
Sampler sampler(_image, side, _lod);
const uint32_t widthMinusOne = sampler.mip.m_width-1;
const uint32_t u0 = uint32_t(uu*widthMinusOne+0.5f);
const uint32_t v0 = uint32_t(vv*widthMinusOne+0.5f);
const uint32_t u1 = bx::min(u0 + 1, widthMinusOne);
const uint32_t v1 = bx::min(v0 + 1, widthMinusOne);
const float fu = bx::fract(uu);
const float fv = bx::fract(vv);
const float fl = bx::fract(_lod);
float rgba00[4];
texelFetch(rgba00, sampler, u0, v0);
float rgbaA[4];
{
Sampler sampler(_image, side, _lod, bx::floor);
const uint32_t widthMinusOne = sampler.mip.m_width-1;
float rgba01[4];
texelFetch(rgba01, sampler, u0, v1);
const uint32_t u0 = uint32_t(uu*widthMinusOne+0.5f);
const uint32_t v0 = uint32_t(vv*widthMinusOne+0.5f);
const uint32_t u1 = bx::min(u0 + 1, widthMinusOne);
const uint32_t v1 = bx::min(v0 + 1, widthMinusOne);
float rgba10[4];
texelFetch(rgba10, sampler, u1, v0);
float rgba00[4];
texelFetch(rgba00, sampler, u0, v0);
float rgba11[4];
texelFetch(rgba11, sampler, u1, v1);
float rgba01[4];
texelFetch(rgba01, sampler, u0, v1);
_rgba[0] = bx::lerp(bx::lerp(rgba00[0], rgba01[0], fv), bx::lerp(rgba10[0], rgba11[0], fv), fu);
_rgba[1] = bx::lerp(bx::lerp(rgba00[1], rgba01[1], fv), bx::lerp(rgba10[1], rgba11[1], fv), fu);
_rgba[2] = bx::lerp(bx::lerp(rgba00[2], rgba01[2], fv), bx::lerp(rgba10[2], rgba11[2], fv), fu);
_rgba[3] = bx::lerp(bx::lerp(rgba00[3], rgba01[3], fv), bx::lerp(rgba10[3], rgba11[3], fv), fu);
float rgba10[4];
texelFetch(rgba10, sampler, u1, v0);
float rgba11[4];
texelFetch(rgba11, sampler, u1, v1);
rgbaA[0] = bx::lerp(bx::lerp(rgba00[0], rgba01[0], fv), bx::lerp(rgba10[0], rgba11[0], fv), fu);
rgbaA[1] = bx::lerp(bx::lerp(rgba00[1], rgba01[1], fv), bx::lerp(rgba10[1], rgba11[1], fv), fu);
rgbaA[2] = bx::lerp(bx::lerp(rgba00[2], rgba01[2], fv), bx::lerp(rgba10[2], rgba11[2], fv), fu);
rgbaA[3] = bx::lerp(bx::lerp(rgba00[3], rgba01[3], fv), bx::lerp(rgba10[3], rgba11[3], fv), fu);
}
float rgbaB[4];
{
Sampler sampler(_image, side, _lod, bx::ceil);
const uint32_t widthMinusOne = sampler.mip.m_width-1;
const uint32_t u0 = uint32_t(uu*widthMinusOne+0.5f);
const uint32_t v0 = uint32_t(vv*widthMinusOne+0.5f);
const uint32_t u1 = bx::min(u0 + 1, widthMinusOne);
const uint32_t v1 = bx::min(v0 + 1, widthMinusOne);
float rgba00[4];
texelFetch(rgba00, sampler, u0, v0);
float rgba01[4];
texelFetch(rgba01, sampler, u0, v1);
float rgba10[4];
texelFetch(rgba10, sampler, u1, v0);
float rgba11[4];
texelFetch(rgba11, sampler, u1, v1);
rgbaB[0] = bx::lerp(bx::lerp(rgba00[0], rgba01[0], fv), bx::lerp(rgba10[0], rgba11[0], fv), fu);
rgbaB[1] = bx::lerp(bx::lerp(rgba00[1], rgba01[1], fv), bx::lerp(rgba10[1], rgba11[1], fv), fu);
rgbaB[2] = bx::lerp(bx::lerp(rgba00[2], rgba01[2], fv), bx::lerp(rgba10[2], rgba11[2], fv), fu);
rgbaB[3] = bx::lerp(bx::lerp(rgba00[3], rgba01[3], fv), bx::lerp(rgba10[3], rgba11[3], fv), fu);
}
_rgba[0] = bx::lerp(rgbaA[0], rgbaB[0], fl);
_rgba[1] = bx::lerp(rgbaA[1], rgbaB[1], fl);
_rgba[2] = bx::lerp(rgbaA[2], rgbaB[2], fl);
_rgba[3] = bx::lerp(rgbaA[3], rgbaB[3], fl);
}
void importanceSampleGgx(float* _result, float _u, float _v, float _roughness, const float* _normal)
@@ -749,6 +792,15 @@ namespace bimg
_result[2] = tangentX[2] * hh[0] + tangentY[2] * hh[1] + _normal[2] * hh[2];
}
float normalDistributionGgx(float _ndoth, float _roughness)
{
const float alpha = bx::square(_roughness);
const float alphaSq = bx::square(alpha);
const float denom = bx::square(_ndoth) * (alphaSq - 1.0f) + 1.0f;
const float denomSq = bx::square(denom);
return alphaSq/(bx::kPi * denomSq);
}
void processFilterAreaGgx(
float* _result
, const ImageContainer& _image
@@ -761,10 +813,11 @@ namespace bimg
imageGetRawData(_image, 0, _lod, _image.m_data, _image.m_size, mip);
const uint32_t bpp = getBitsPerPixel(_image.m_format);
const float lod = float(_lod)/_image.m_numMips;
constexpr int32_t kNumSamples = 64;
const uint32_t pitch = mip.m_width*bpp/8;
const float widthMinusOne = float(mip.m_width-1);
const float mipBias = 0.5f*bx::log2(bx::square(float(mip.m_width) )/float(kNumSamples) );
UnpackFn unpack = getUnpack(_image.m_format);
@@ -773,9 +826,9 @@ namespace bimg
bx::RngMwc mwc;
for (uint32_t ii = 0; ii < 1024; ++ii)
for (uint32_t ii = 0; ii < kNumSamples; ++ii)
{
const float uu = ii/1024.0f;
const float uu = ii/float(kNumSamples);
const float vv = bx::frnd(&mwc);
float hh[3];
@@ -792,6 +845,14 @@ namespace bimg
if (ndotl > 0.0f)
{
const float ndoth = ndotl;
const float vdoth = ndotl;
// Chapter 20. GPU-Based Importance Sampling
// http://archive.today/2018.07.14-004914/https://developer.nvidia.com/gpugems/GPUGems3/gpugems3_ch20.html
const float pdf = normalDistributionGgx(ndoth, _roughness) * ndoth / (4.0f * vdoth);
const float lod = bx::max(0.0f, mipBias - 0.5f*bx::log2(pdf) );
float rgba[4];
sampleCubeMap(rgba, _image, ll, lod);
@@ -1061,7 +1122,12 @@ namespace bimg
for (uint8_t lod = 1, numMips = input->m_numMips; lod < numMips; ++lod)
{
ImageContainer* nsa = imageCubemapNormalSolidAngle(_allocator, bx::max<uint32_t>(_image.m_width>>lod, 1) );
ImageContainer* nsa = NULL;
if (LightingModel::Ggx != _lightingModel)
{
nsa = imageCubemapNormalSolidAngle(_allocator, bx::max<uint32_t>(_image.m_width>>lod, 1) );
}
for (uint8_t side = 0; side < 6; ++side)
{
@@ -1110,7 +1176,10 @@ namespace bimg
}
}
imageFree(nsa);
if (NULL != nsa)
{
imageFree(nsa);
}
}
return output;