public static unsafe bool Hit(this BvhNode n, NativeArray <Entity> entities, Ray r, float tMin, float tMax,
ref Random rng, AccumulateJob.WorkingArea wa,
#if FULL_DIAGNOSTICS
ref Diagnostics diagnostics,
#endif
out HitRecord rec)
{
int candidateCount = 0, nodeStackHeight = 1;
BvhNode **nodeStackTail = wa.Nodes;
Entity * candidateListTail = wa.Entities - 1, candidateListHead = wa.Entities;
float3 rayInvDirection = rcp(r.Direction);
*nodeStackTail = &n;
while (nodeStackHeight > 0)
{
BvhNode *nodePtr = *nodeStackTail--;
nodeStackHeight--;
if (!nodePtr->Bounds.Hit(r.Origin, rayInvDirection, tMin, tMax))
{
continue;
}
#if FULL_DIAGNOSTICS
diagnostics.BoundsHitCount++;
#endif
if (nodePtr->IsLeaf)
{
*++candidateListTail = entities[nodePtr->EntityId];
candidateCount++;
}
else
{
*++nodeStackTail = nodePtr->Left;
*++nodeStackTail = nodePtr->Right;
nodeStackHeight += 2;
}
}
#if FULL_DIAGNOSTICS
diagnostics.CandidateCount = candidateCount;
#endif
if (candidateCount == 0)
{
rec = default;
return(false);
}
#if BVH_SIMD
// TODO: this is fully broken
// skip SIMD codepath if there's only one
if (candidateCount == 1)
{
return(candidateListHead->Hit(r, tMin, tMax, out rec));
}
var simdSpheresHead = (Sphere4 *)wa.Vectors;
int simdBlockCount = (int)ceil(candidateCount / 4.0f);
float4 a = dot(r.Direction, r.Direction);
int4 curId = int4(0, 1, 2, 3), hitId = -1;
float4 hitT = tMax;
Sphere4 *blockCursor = simdSpheresHead;
Entity * candidateCursor = candidateListHead;
int candidateIndex = 0;
for (int i = 0; i < simdBlockCount; i++)
{
for (int j = 0; j < 4; j++)
{
if (candidateIndex < candidateCount)
{
Sphere *sphereData = candidateCursor->AsSphere;
float3 center = sphereData->Center(r.Time);
blockCursor->CenterX[j] = center.x;
blockCursor->CenterY[j] = center.y;
blockCursor->CenterZ[j] = center.z;
blockCursor->SquaredRadius[j] = sphereData->SquaredRadius;
++candidateCursor;
++candidateIndex;
}
else
{
blockCursor->CenterX[j] = float.MaxValue;
blockCursor->CenterY[j] = float.MaxValue;
blockCursor->CenterZ[j] = float.MaxValue;
blockCursor->SquaredRadius[j] = 0;
}
}
float4 ocX = r.Origin.x - blockCursor->CenterX,
ocY = r.Origin.y - blockCursor->CenterY,
ocZ = r.Origin.z - blockCursor->CenterZ;
float4 b = ocX * r.Direction.x + ocY * r.Direction.y + ocZ * r.Direction.z;
float4 c = ocX * ocX + ocY * ocY + ocZ * ocZ - blockCursor->SquaredRadius;
float4 discriminant = b * b - a * c;
bool4 discriminantTest = discriminant > 0;
if (any(discriminantTest))
{
float4 sqrtDiscriminant = sqrt(discriminant);
float4 t0 = (-b - sqrtDiscriminant) / a;
float4 t1 = (-b + sqrtDiscriminant) / a;
float4 t = select(t1, t0, t0 > tMin);
bool4 mask = discriminantTest & t > tMin & t < hitT;
hitId = select(hitId, curId, mask);
hitT = select(hitT, t, mask);
}
curId += 4;
++blockCursor;
}
if (all(hitId == -1))
{
rec = default;
return(false);
}
float minDistance = cmin(hitT);
int laneMask = bitmask(hitT == minDistance);
int firstLane = tzcnt(laneMask);
int closestId = hitId[firstLane];
Sphere *closestSphere = candidateListHead[closestId].AsSphere;
float3 point = r.GetPoint(minDistance);
rec = new HitRecord(minDistance, point,
(point - closestSphere->Center(r.Time)) / closestSphere->Radius,
closestSphere->Material);
return(true);
#else
// iterative candidate tests (non-SIMD)
bool anyHit = candidateListHead->Hit(r, tMin, tMax, ref rng, out rec);
for (int i = 1; i < candidateCount; i++)
{
bool thisHit = candidateListHead[i].Hit(r, tMin, tMax, ref rng, out HitRecord thisRec);
if (thisHit && (!anyHit || thisRec.Distance < rec.Distance))
{
anyHit = true;
rec = thisRec;
}
}
if (anyHit)
{
return(true);
}
rec = default;
return(false);
#endif
}
public bool Scatter(Ray ray, HitRecord rec, ref Random rng, PerlinData perlinData,
out float3 reflectance, out Ray scattered)
{
switch (Type)
{
case MaterialType.Lambertian:
{
reflectance = Texture.Value(rec.Point, rec.Normal, TextureScale, perlinData);
float3 randomDirection = rng.OnCosineWeightedHemisphere(rec.Normal);
scattered = new Ray(rec.Point, randomDirection, ray.Time);
return(true);
}
case MaterialType.Metal:
{
float3 outgoingDirection = WorldToTangentSpace(-ray.Direction, rec.Normal);
if (GgxMicrofacet.ImportanceSample(Texture.Value(rec.Point, rec.Normal, TextureScale, perlinData),
Roughness, ref rng, outgoingDirection, out float3 toLight, out reflectance))
{
float3 scatterDirection = TangentToWorldSpace(toLight, rec.Normal);
scattered = new Ray(rec.Point, scatterDirection, ray.Time);
return(true);
}
scattered = default;
return(false);
}
case MaterialType.Dielectric:
{
float3 reflected = reflect(ray.Direction, rec.Normal);
reflectance = 1;
float niOverNt;
float3 outwardNormal;
float cosine;
if (dot(ray.Direction, rec.Normal) > 0)
{
outwardNormal = -rec.Normal;
niOverNt = RefractiveIndex;
cosine = RefractiveIndex * dot(ray.Direction, rec.Normal);
}
else
{
outwardNormal = rec.Normal;
niOverNt = 1 / RefractiveIndex;
cosine = -dot(ray.Direction, rec.Normal);
}
if (Refract(ray.Direction, outwardNormal, niOverNt, out float3 refracted))
{
float reflectProb = Schlick(cosine, RefractiveIndex);
scattered = new Ray(rec.Point, rng.NextFloat() < reflectProb ? reflected : refracted, ray.Time);
}
else
{
scattered = new Ray(rec.Point, reflected, ray.Time);
}
return(true);
}
case MaterialType.ProbabilisticVolume:
scattered = new Ray(rec.Point, rng.NextFloat3Direction());
reflectance = Texture.Value(rec.Point, rec.Normal, TextureScale, perlinData);
return(true);
default:
reflectance = default;
scattered = default;
return(false);
}
}
// iterative entity array hit test
public static bool Hit(this NativeArray <Entity> entities, Ray r, float tMin, float tMax, ref Random rng, out HitRecord rec)
{
bool hitAnything = false;
rec = new HitRecord(tMax, 0, 0, default);
for (var i = 0; i < entities.Length; i++)
{
if (entities[i].Hit(r, tMin, rec.Distance, ref rng, out HitRecord thisRec))
{
hitAnything = true;
rec = thisRec;
}
}
return(hitAnything);
}
public unsafe void Sample(Ray materialScatterRay, float3 outgoingLightDirection, HitRecord rec, Material material, ref Random rng,
out Ray scatterRay, out float pdfValue, out int?targetEntityId)
{
int totalOptions = TargetEntities.Length + (Mode == ImportanceSamplingMode.Mixture ? 1 : 0);
int chosenOption = rng.NextInt(0, totalOptions);
if (chosenOption == TargetEntities.Length)
{
scatterRay = materialScatterRay;
targetEntityId = null;
}
else
{
Entity *chosenEntity = (Entity *)TargetEntities.GetUnsafeReadOnlyPtr() + chosenOption;
float3 pointOnEntity = chosenEntity->RandomPoint(materialScatterRay.Time, ref rng);
scatterRay = new Ray(materialScatterRay.Origin,
normalize(pointOnEntity - materialScatterRay.Origin));
targetEntityId = chosenEntity->Id;
}
pdfValue = 0;
if (Mode == ImportanceSamplingMode.Mixture)
{
pdfValue += material.Pdf(scatterRay.Direction, outgoingLightDirection, rec.Normal);
}
var basePointer = (Entity *)TargetEntities.GetUnsafeReadOnlyPtr();
for (int i = 0; i < TargetEntities.Length; i++)
{
pdfValue += (basePointer + i)->Pdf(scatterRay, ref rng);
}
pdfValue /= totalOptions;
}