/// standard object services ---------------------------------------------------
public Scene(StreamReader infile, Vector eyePosition)
{
// read and condition default sky and ground values
skyEmission = new Vector(infile);
groundReflection = new Vector(infile);
skyEmission = skyEmission.Clamp(Vector.ZERO, skyEmission);
groundReflection = skyEmission * groundReflection.Clamp(Vector.ZERO, Vector.ONE);
triangles = new List<Triangle>();
emitters = new List<Triangle>();
// read objects
while (infile.EndOfStream == false)
{
Triangle t = new Triangle(infile);
if (t.Area != 0)
triangles.Add(t);
}
// find emitting triangles
foreach (Triangle t in triangles)
{
if (!t.Emitivity.IsZero() && (t.Area > 0.0f))
{
emitters.Add(t);
if (emitters.Count >= (1 << MAX_EMITTERS_P))
break;
}
}
// make index
octtree = new Spatial(eyePosition, triangles);
}
public Vector GetRadiance(Vector rayOrigin, Vector rayDirection, Sampler random, Triangle lastHit)
{
// intersect ray with scene
Triangle pHitObject;
Vector hitPosition;
scene.GetIntersection(rayOrigin, rayDirection, lastHit, out pHitObject, out hitPosition);
Vector radiance;
if (null != pHitObject)
{
// make surface point of intersection
SurfacePoint surfacePoint = new SurfacePoint(pHitObject, hitPosition);
// local emission only for first-hit
if (lastHit != null)
radiance = Vector.ZERO;
else
radiance = surfacePoint.GetEmission(rayOrigin, -rayDirection, false);
// add emitter sample
radiance = radiance + SampleEmitters(rayDirection, surfacePoint, random);
// add recursive reflection
//
// single hemisphere sample, ideal diffuse BRDF:
// reflected = (inradiance * pi) * (cos(in) / pi * color) * reflectance
// -- reflectance magnitude is 'scaled' by the russian roulette, cos is
// importance sampled (both done by SurfacePoint), and the pi and 1/pi
// cancel out
Vector nextDirection;
Vector color;
// check surface bounces ray, recurse
if (surfacePoint.GetNextDirection(random, -rayDirection, out nextDirection, out color))
radiance = radiance + (color * GetRadiance(surfacePoint.Position, nextDirection, random, surfacePoint.Item));
}
else // no hit: default/background scene emission
radiance = scene.GetDefaultEmission(-rayDirection);
return radiance;
}
public void GetIntersection(
Vector rayOrigin, Vector rayDirection, Triangle lastHit,
out Triangle pHitObject, out Vector hitPosition, Vector pStart)
{
hitPosition = null;
pHitObject = null;
// is branch: step through subcells and recurse
if (isBranch)
{
if (pStart == null)
pStart = rayOrigin;
// find which subcell holds ray origin (ray origin is inside cell)
int subCell = 0;
for (int i = 3; i-- > 0; )
{
// compare dimension with center
if (pStart[i] >= ((bound[i] + bound[i + 3]) * 0.5f))
subCell |= 1 << i;
}
// step through intersected subcells
Vector cellPosition = new Vector(pStart);
for (; ; )
{
if (null != spatial[subCell])
{
// intersect subcell
spatial[subCell].GetIntersection(rayOrigin, rayDirection, lastHit, out pHitObject, out hitPosition, cellPosition);
// exit if item hit
if (null != pHitObject)
break;
}
// find next subcell ray moves to
// (by finding which face of the corner ahead is crossed first)
int axis = 2;
float[] step = new float[3]; // todo - move this allocation?
for (int i = 3; i-- > 0; axis = step[i] < step[axis] ? i : axis)
{
bool high = ((subCell >> i) & 1) != 0;
float face = (rayDirection[i] < 0.0f) ^ high ? bound[i + ((high ? 1 : 0) * 3)] : (bound[i] + bound[i + 3]) * 0.5f;
// distance to face
// (div by zero produces infinity, which is later discarded)
step[i] = (face - rayOrigin[i]) / rayDirection[i];
}
// leaving branch if: subcell is low and direction is negative,
// or subcell is high and direction is positive
if ((((subCell >> axis) & 1) != 0) ^ (rayDirection[axis] < 0.0f))
break;
// move to (outer face of) next subcell
cellPosition = rayOrigin + (rayDirection * step[axis]);
subCell = subCell ^ (1 << axis);
}
}
else
{ // is leaf: exhaustively intersect contained items
float nearestDistance = float.MaxValue;
// step through items
foreach (Triangle item in triangles)
{
// avoid false intersection with surface just come from
if (item != lastHit)
{
// intersect ray with item, and inspect if nearest so far
float distance = float.MaxValue;
if (item.GetIntersection(rayOrigin, rayDirection, ref distance) && (distance < nearestDistance))
{
// check intersection is inside cell bound (with tolerance)
Vector hit = rayOrigin + (rayDirection * distance);
float t = Triangle.TOLERANCE;
if ((bound[0] - hit[0] <= t) && (hit[0] - bound[3] <= t) &&
(bound[1] - hit[1] <= t) && (hit[1] - bound[4] <= t) &&
(bound[2] - hit[2] <= t) && (hit[2] - bound[5] <= t))
{
pHitObject = item;
nearestDistance = distance;
hitPosition = hit;
}
}
}
}
}
}
public void GetEmitter(Sampler random, out Vector position, out Triangle triangle)
{
if (emitters.Count != 0)
{
// select emitter
// not using lower bits, by treating the random as fixed-point i.f bits
int index = ((((int)(int.MaxValue*random.GetNextSample()) & ((1 << MAX_EMITTERS_P) - 1)) * emitters.Count) >> MAX_EMITTERS_P);
// get position on triangle
position = emitters[index].GetSamplePoint(random);
triangle = emitters[index];
}
else
{
position = Vector.ZERO;
triangle = null;
}
}
public void GetIntersection(
Vector rayOrigin, Vector rayDirection, Triangle lastHit,
out Triangle pHitObject, out Vector hitPosition)
{
octtree.GetIntersection(rayOrigin, rayDirection, lastHit, out pHitObject, out hitPosition, null);
}