private int BoxCompare(IHittable a, IHittable b, int axis)
{
var boxA = a.BoundingBox();
var boxB = b.BoundingBox();
return(boxA.Min[axis].CompareTo(boxB.Min[axis]));
}
private static int BoxCompare(IHittable a, IHittable b, int axis)
{
if (!a.BoundingBox(0, 1, out var boxA) ||
!b.BoundingBox(0, 1, out var boxB))
{
throw new Exception("No bounding box found in BoxCompare!");
}
return(boxA.Min[axis].CompareTo(boxB.Min[axis]));
}
public bool BoundingBox(double t0, double t1, out Aabb outputBox)
{
if (!Child.BoundingBox(t0, t1, out outputBox))
{
return(false);
}
outputBox = new Aabb
{
Min = outputBox.Min + Offset,
Max = outputBox.Max + Offset
};
return(true);
}
public RotateY(IHittable child, double angle)
{
Child = child;
var radians = MathUtils.Deg2Rad(angle);
SinTheta = Math.Sin(radians);
CosTheta = Math.Cos(radians);
HasBox = Child.BoundingBox(0, 1, out var box);
var min = new Vec3(MathUtils.Infinity, MathUtils.Infinity, MathUtils.Infinity);
var max = new Vec3(-MathUtils.Infinity, -MathUtils.Infinity, -MathUtils.Infinity);
for (var i = 0; i < 2; i++)
{
for (var j = 0; j < 2; j++)
{
for (var k = 0; k < 2; k++)
{
var x = i * box.Max.x + (1 - i) * box.Min.x;
var y = j * box.Max.y + (1 - j) * box.Min.y;
var z = k * box.Max.z + (1 - k) * box.Min.z;
var newX = CosTheta * x + SinTheta * z;
var newZ = -SinTheta * x + CosTheta * z;
var tester = new Vec3(newX, y, newZ);
for (int c = 0; c < 3; c++)
{
min[c] = Math.Min(min[c], tester[c]);
max[c] = Math.Max(max[c], tester[c]);
}
}
}
}
BBox = new Aabb
{
Min = min,
Max = max
};
}
// https://raytracing.github.io/books/RayTracingTheNextWeek.html#boundingvolumehierarchies
public BvhNode(List <IHittable> srcObjects, int start, int end, AbstractSampler <int> sampler = null)
{
sampler ??= new ThreadSafeSampler <int>(count => IntSampling.Random(count, 0, 3), SAMPLES);
var objects = srcObjects;
int axis = sampler.GetSample();
int Comparator(IHittable a, IHittable b) => BoxCompare(a, b, axis);
int objectSpan = end - start;
switch (objectSpan)
{
case 1:
_left = _right = objects[start];
break;
case 2 when Comparator(objects[start], objects[start + 1]) < 0:
_left = objects[start];
_right = objects[start + 1];
break;
case 2:
_left = objects[start + 1];
_right = objects[start];
break;
default:
objects.Sort(start, objectSpan - 1, new FuncComparer <IHittable>(Comparator));
int mid = start + objectSpan / 2;
_left = new BvhNode(objects, start, mid, sampler);
_right = new BvhNode(objects, mid, end, sampler);
break;
}
var boxLeft = _left.BoundingBox();
var boxRight = _right.BoundingBox();
_box = boxLeft + boxRight;
}
public BvhNode(List <IHittable> srcObjects, int start, int end, double t0, double t1)
{
var min = new Vec3(MathUtils.Infinity, MathUtils.Infinity, MathUtils.Infinity);
var max = new Vec3(-MathUtils.Infinity, -MathUtils.Infinity, -MathUtils.Infinity);
for (var i = start; i < end; i++)
{
srcObjects[i].BoundingBox(t0, t1, out var box);
if (box.Min.x < min.x)
{
min.x = box.Min.x;
}
if (box.Min.y < min.y)
{
min.y = box.Min.y;
}
if (box.Min.z < min.z)
{
min.z = box.Min.z;
}
if (box.Max.x > max.x)
{
max.x = box.Max.x;
}
if (box.Max.y > max.y)
{
max.y = box.Max.y;
}
if (box.Max.z > max.z)
{
max.z = box.Max.z;
}
}
var diffs = max - min;
var axis = 0;
if (diffs.y > diffs.x && diffs.y > diffs.z)
{
axis = 1;
}
if (diffs.z > diffs.x && diffs.z > diffs.y)
{
axis = 2;
}
IComparer <IHittable> comparator;
switch (axis)
{
case 0: comparator = new BoxCompareX(); break;
case 1: comparator = new BoxCompareY(); break;
default: comparator = new BoxCompareZ(); break;
}
var objSpan = end - start;
if (objSpan == 1)
{
Left = srcObjects[start];
Right = srcObjects[start];
}
else if (objSpan == 2)
{
if (comparator.Compare(srcObjects[start], srcObjects[start + 1]) < 0)
{
Left = srcObjects[start];
Right = srcObjects[start + 1];
}
else
{
Left = srcObjects[start + 1];
Right = srcObjects[start];
}
}
else
{
srcObjects.Sort(start, objSpan, comparator);
var mid = start + objSpan / 2;
Left = new BvhNode(srcObjects, start, mid, t0, t1);
Right = new BvhNode(srcObjects, mid, end, t0, t1);
}
if (!Left.BoundingBox(t0, t1, out var boxLeft) ||
!Right.BoundingBox(t0, t1, out var boxRight))
{
throw new Exception("No bounding box in BvhNode constructor");
}
Box = Aabb.SurroundingBox(boxLeft, boxRight);
}
public bool BoundingBox(double t0, double t1, out Aabb outputBox)
{
return(Boundary.BoundingBox(t0, t1, out outputBox));
}
