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Fix DiskLight injects too much energy when sampling a texture #20

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Fix DiskLight injects too much energy when sampling a texture #20

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59 changes: 8 additions & 51 deletions lib/rendering/pbr/light/DiskLight.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -414,34 +414,10 @@ DiskLight::sample(const Vec3f &p, const Vec3f *n, float time, const Vec3f& r,
// we are in a good region to sample the spread, then sample that region.
// 3) Otherwise, sample the shape of the light.
if (mDistribution) {
// Sample the image distribution if any

// This type of technique is bad for for vector processors in general
// since some lanes will go idle as the rejection loop still needs to
// iterate for other lanes. It should work fine here though because the
// distribution has been prebuilt with a low probability of sampling
// outside of the inscribed circle by using ImageDistribution::CIRCULAR.
// This should ensure we only loop rarely.
const unsigned maxTries = 8;
unsigned attempts = 0;
while(attempts != maxTries) {
mDistribution->sample(r1, r2, 0, &isect.uv, nullptr, mTextureFilter);
float x = isect.uv.x * 2.0f - 1.0f;
float y = isect.uv.y * 2.0f - 1.0f;
if (x*x + y*y < 1.0f) {
break;
}

// Generate new random numbers based on these ones.
// TODO: this is hacky code, do a better job of generating
// further random numbers
r1 = scene_rdl2::math::fmod(r1 + 0.789f, 1.0f);
r2 = scene_rdl2::math::fmod(r2 + 0.331f, 1.0f);

attempts++;
}

if (attempts == maxTries) {
mDistribution->sample(r1, r2, 0, &isect.uv, nullptr, mTextureFilter);
float x = isect.uv.x * 2.0f - 1.0f;
float y = isect.uv.y * 2.0f - 1.0f;
if (x*x + y*y >= 1.0f) {
return false;
}

Expand Down Expand Up @@ -584,29 +560,10 @@ DiskLight::getEquiAngularPivot(const Vec3f& r, float time) const
float r2 = r[1];
// Sample the image distribution if any
if (mDistribution) {
// This type of technique is bad for for vector processors in general
// since some lanes will go idle as the rejection loop still needs to
// iterate for other lanes. It should work fine here though because the
// distribution has been prebuilt with a low probability of sampling
// outside of the inscribed circle by using ImageDistribution::CIRCULAR.
// This should ensure we only loop rarely.
const unsigned maxTries = 8;
unsigned attempts = 0;
while(attempts != maxTries) {
mDistribution->sample(r1, r2, 0, &uv, nullptr, mTextureFilter);
float x = uv.x * 2.0f - 1.0f;
float y = uv.y * 2.0f - 1.0f;
if (x*x + y*y < 1.0f) {
break;
}
// Generate new random numbers based on these ones.
// TODO: this is hacky code, do a better job of generating
// further random numbers
r1 = scene_rdl2::math::fmod(r1 + 0.789f, 1.0f);
r2 = scene_rdl2::math::fmod(r2 + 0.331f, 1.0f);
attempts++;
}
if (attempts == maxTries) {
mDistribution->sample(r1, r2, 0, &uv, nullptr, mTextureFilter);
float x = uv.x * 2.0f - 1.0f;
float y = uv.y * 2.0f - 1.0f;
if (x*x + y*y >= 1.0f) {
return getPosition(time);
}
hit = Vec3f((uv[0] - mUvOffset.x) / mUvScale.x,
Expand Down
31 changes: 4 additions & 27 deletions lib/rendering/pbr/light/DiskLight.ispc
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Original file line number Diff line number Diff line change
Expand Up @@ -268,33 +268,10 @@ DiskLight_sample(const uniform Light * uniform li,
// we are in a good region to sample the spread, then sample that region.
// 3) Otherwise, sample the shape of the light.
if (light->mDistribution) {
// Sample the image distribution if any

// This type of technique is bad for for vector processors in general
// since some lanes will go idle as the rejection loop still needs to
// iterate for other lanes. It should work fine here though because the
// distribution has been pre-built with a low probability of sampling
// outside of the inscribed circle by using ImageDistribution::CIRCULAR.
// This should ensure we only loop rarely.
const uniform uint32_t maxTries = 8;
uniform uint32_t attempts = 0;
while (attempts != maxTries) {
ImageDistribution_sample(light->mDistribution, r1, r2, 0, &isect.uv, nullptr, light->mTextureFilter);
float x = isect.uv.x * 2.0f - 1.0f;
float y = isect.uv.y * 2.0f - 1.0f;
if (x*x + y*y < 1.0f) {
break;
}

// Generate new random numbers based on these ones.
// TODO: this is hacky code, do a better job of generating
// further random numbers
r1 = fmod(r1 + 0.789f, 1.0f);
r2 = fmod(r2 + 0.331f, 1.0f);
attempts++;
}

if (attempts == maxTries) {
ImageDistribution_sample(light->mDistribution, r1, r2, 0, &isect.uv, nullptr, light->mTextureFilter);
float x = isect.uv.x * 2.0f - 1.0f;
float y = isect.uv.y * 2.0f - 1.0f;
if (x*x + y*y >= 1.0f) {
return false;
}

Expand Down