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Modified cascade distance distribution to blend between a desired resolution and an automatic logarithm distribution

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Olivier Prat 2017-12-06 10:48:04 +01:00
parent 1d8d8335c5
commit f9641afcd0
1 changed files with 32 additions and 23 deletions
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55
libraries/render-utils/src/LightStage.cpp
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@ -102,41 +102,50 @@ LightStage::Shadow::Shadow(model::LightPointer light, float maxDistance, unsigne
}
void LightStage::Shadow::setMaxDistance(float value) {
_maxDistance = std::max(0.0f, value);
static const auto OVERLAP_FACTOR = 1.0f / 4.0f;
// Distribute the cascades along that distance
// TODO : these parameters should be exposed to the user as part of the light entity parameters, no?
static const auto LOW_CASCADE_MAX_DISTANCE = 1.5f;
// Power distribution. Lower the steepness to 1.0 for a more linear distribution or increase it for a
// tighter distribution around the view position.
static const auto CASCADE_DISTRIBUTION_STEEPNESS = 3.0f;
_maxDistance = std::max(0.0f, value);
if (_cascades.size() == 1) {
_cascades.front().setMinDistance(0.0f);
_cascades.front().setMaxDistance(_maxDistance);
} else {
// Distribute the cascades along that distance
// TODO : these parameters should be exposed to the user as part of the light entity parameters, no?
static const auto LOW_MAX_DISTANCE = 2.0f;
static const auto MAX_RESOLUTION_LOSS = 0.6f; // Between 0 and 1, 0 giving tighter distributions
// The max cascade distance is computed by multiplying the previous cascade's max distance by a certain
// factor. There is a "user" factor that is computed from a desired max resolution loss in the shadow
// and an optimal own based on the global min and max shadow distance, all cascades considered. The final
// distance is a gradual blend between the two
const auto userDistanceScale = 1.0f / (1.0f - MAX_RESOLUTION_LOSS);
const auto optimalDistanceScale = powf(_maxDistance / LOW_MAX_DISTANCE, 1.0f / (_cascades.size() - 1));
float maxCascadeUserDistance = LOW_MAX_DISTANCE;
float maxCascadeOptimalDistance = LOW_MAX_DISTANCE;
float minCascadeDistance = 0.0f;
for (auto cascadeIndex = 0; cascadeIndex < _cascades.size(); ++cascadeIndex) {
float blendFactor = cascadeIndex / float(_cascades.size() - 1);
float maxCascadeDistance;
float minCascadeDistance;
float shadowOverlapDistance;
const auto deltaCascadeMaxDistance = (_maxDistance - LOW_CASCADE_MAX_DISTANCE);
const auto maxAlpha = powf(cascadeIndex / float(_cascades.size() - 1), CASCADE_DISTRIBUTION_STEEPNESS);
const auto minAlpha = powf(std::max<float>(cascadeIndex - 1, 0) / float(_cascades.size() - 1), CASCADE_DISTRIBUTION_STEEPNESS);
maxCascadeDistance = LOW_CASCADE_MAX_DISTANCE + deltaCascadeMaxDistance * maxAlpha;
minCascadeDistance = LOW_CASCADE_MAX_DISTANCE + deltaCascadeMaxDistance * minAlpha;
if (cascadeIndex == 0) {
minCascadeDistance = 0.0f;
if (cascadeIndex == _cascades.size() - 1) {
maxCascadeDistance = _maxDistance;
} else {
minCascadeDistance = std::max(minCascadeDistance, 0.0f);
maxCascadeDistance = maxCascadeUserDistance + (maxCascadeOptimalDistance - maxCascadeUserDistance)*blendFactor;
}
shadowOverlapDistance = (maxCascadeDistance - minCascadeDistance) / 3.0f;
maxCascadeDistance += shadowOverlapDistance;
float shadowOverlapDistance = (maxCascadeDistance - minCascadeDistance) * OVERLAP_FACTOR;
_cascades[cascadeIndex].setMinDistance(minCascadeDistance);
_cascades[cascadeIndex].setMaxDistance(maxCascadeDistance);
_cascades[cascadeIndex].setMaxDistance(maxCascadeDistance + shadowOverlapDistance);
// Compute distances for next cascade
minCascadeDistance = maxCascadeDistance;
maxCascadeUserDistance = maxCascadeUserDistance * userDistanceScale;
maxCascadeOptimalDistance = maxCascadeOptimalDistance * optimalDistanceScale;
maxCascadeUserDistance = std::min(maxCascadeUserDistance, _maxDistance);
}
}
@ -144,7 +153,7 @@ void LightStage::Shadow::setMaxDistance(float value) {
const auto& lastCascade = _cascades.back();
auto& schema = _schemaBuffer.edit<Schema>();
schema.maxDistance = _maxDistance;
schema.invFalloffDistance = 3.0f / (lastCascade.getMaxDistance() - lastCascade.getMinDistance());
schema.invFalloffDistance = 1.0f / (OVERLAP_FACTOR*(lastCascade.getMaxDistance() - lastCascade.getMinDistance()));
}
void LightStage::Shadow::setKeylightFrustum(unsigned int cascadeIndex, const ViewFrustum& viewFrustum,