source-engine/raytrace/raytrace.cpp

//========= Copyright Valve Corporation, All rights reserved. ============//
// $Id$

#include "raytrace.h"
#include <filesystem_tools.h>
#include <cmdlib.h>
#include <stdio.h>

static bool SameSign(float a, float b)
{
	int32 aa=*((int *) &a);
	int32 bb=*((int *) &b);
	return ((aa^bb)&0x80000000)==0;
}

int FourRays::CalculateDirectionSignMask(void) const
{
	// this code treats the floats as integers since all it cares about is the sign bit and
	// floating point compares suck.

	int ret;
	int ormask;
	int andmask;
	int32 const *treat_as_int=((int32 const *) (&direction));

	ormask=andmask=*(treat_as_int++);
	ormask|=*treat_as_int;
	andmask&=*(treat_as_int++);
	ormask|=*(treat_as_int);
	andmask&=*(treat_as_int++);
	ormask|=*(treat_as_int);
	andmask&=*(treat_as_int++);
	if (ormask>=0)
		ret=0;
	else
	{
		if (andmask<0)
			ret=1;
		else return -1;
	}
	ormask=andmask=*(treat_as_int++);
	ormask|=*treat_as_int;
	andmask&=*(treat_as_int++);
	ormask|=*(treat_as_int);
	andmask&=*(treat_as_int++);
	ormask|=*(treat_as_int);
	andmask&=*(treat_as_int++);
	if (ormask<0)
	{
		if (andmask<0)
			ret|=2;
		else return -1;
	}
	ormask=andmask=*(treat_as_int++);
	ormask|=*treat_as_int;
	andmask&=*(treat_as_int++);
	ormask|=*(treat_as_int);
	andmask&=*(treat_as_int++);
	ormask|=*(treat_as_int);
	andmask&=*(treat_as_int++);
	if (ormask<0)
	{
		if (andmask<0)
			ret|=4;
		else return -1;
	}
	return ret;
}




void RayTracingEnvironment::MakeRoomForTriangles( int ntris )
{
	//OptimizedTriangleList.EnsureCapacity( ntris );
	if (! (Flags & RTE_FLAGS_DONT_STORE_TRIANGLE_COLORS))
		TriangleColors.EnsureCapacity( ntris );
}


void RayTracingEnvironment::AddTriangle(int32 id, const Vector &v1,
										const Vector &v2, const Vector &v3,
										const Vector &color)
{
	AddTriangle( id, v1, v2, v3, color, 0, 0 );
}

void RayTracingEnvironment::AddTriangle(int32 id, const Vector &v1,
										const Vector &v2, const Vector &v3,
										const Vector &color, uint16 flags, int32 materialIndex)
{
	CacheOptimizedTriangle tmptri;
	tmptri.m_Data.m_GeometryData.m_nTriangleID = id;
	tmptri.Vertex( 0 ) = v1;
	tmptri.Vertex( 1 ) = v2;
	tmptri.Vertex( 2 ) = v3;
	tmptri.m_Data.m_GeometryData.m_nFlags = flags;
	OptimizedTriangleList.AddToTail(tmptri);
	if (! ( Flags & RTE_FLAGS_DONT_STORE_TRIANGLE_COLORS) )
		TriangleColors.AddToTail(color);
	if ( !( Flags & RTE_FLAGS_DONT_STORE_TRIANGLE_MATERIALS) )
		TriangleMaterials.AddToTail(materialIndex);
// 	printf("add triange from (%f %f %f),(%f %f %f),(%f %f %f) id %d\n",
// 		   XYZ(v1),XYZ(v2),XYZ(v3),id);
}

void RayTracingEnvironment::AddQuad(
	int32 id, const Vector &v1, const Vector &v2, const Vector &v3,
	const Vector &v4,							// specify vertices in cw or ccw order
	const Vector &color)
{
	AddTriangle(id,v1,v2,v3,color);
	AddTriangle(id+1,v1,v3,v4,color);
}


void RayTracingEnvironment::AddAxisAlignedRectangularSolid(int id,Vector minc, Vector maxc,
														   const Vector &color)
{

	// "far" face
	AddQuad(id,
			Vector(minc.x,maxc.y,maxc.z),
			Vector(maxc.x,maxc.y,maxc.z),Vector(maxc.x,minc.y,maxc.z),
			Vector(minc.x,minc.y,maxc.z),color);
	// "near" face
	AddQuad(id,
			Vector(minc.x,maxc.y,minc.z),
			Vector(maxc.x,maxc.y,minc.z),Vector(maxc.x,minc.y,minc.z),
			Vector(minc.x,minc.y,minc.z),color);

	// "left" face
	AddQuad(id,
			Vector(minc.x,maxc.y,maxc.z),
			Vector(minc.x,maxc.y,minc.z),
			Vector(minc.x,minc.y,minc.z),
			Vector(minc.x,minc.y,maxc.z),color);
	// "right" face
	AddQuad(id,
			Vector(maxc.x,maxc.y,maxc.z),
			Vector(maxc.x,maxc.y,minc.z),
			Vector(maxc.x,minc.y,minc.z),
			Vector(maxc.x,minc.y,maxc.z),color);
	
	// "top" face
	AddQuad(id,
			Vector(minc.x,maxc.y,maxc.z),
			Vector(maxc.x,maxc.y,maxc.z),
			Vector(maxc.x,maxc.y,minc.z),
			Vector(minc.x,maxc.y,minc.z),color);
	// "bot" face
	AddQuad(id,
			Vector(minc.x,minc.y,maxc.z),
			Vector(maxc.x,minc.y,maxc.z),
			Vector(maxc.x,minc.y,minc.z),
			Vector(minc.x,minc.y,minc.z),color);
}



static Vector GetEdgeEquation(Vector p1, Vector p2, int c1, int c2, Vector InsidePoint)
{
	float nx=p1[c2]-p2[c2];
	float ny=p2[c1]-p1[c1];
	float d=-(nx*p1[c1]+ny*p1[c2]);
// 	assert(fabs(nx*p1[c1]+ny*p1[c2]+d)<0.01);
// 	assert(fabs(nx*p2[c1]+ny*p2[c2]+d)<0.01);

	// use the convention that negative is "outside"
	float trial_dist=InsidePoint[c1]*nx+InsidePoint[c2]*ny+d;
	if (trial_dist<0)
	{
		nx = -nx;
		ny = -ny;
		d = -d;
		trial_dist = -trial_dist;
	}
	nx /= trial_dist;										// scale so that it will be =1.0 at the oppositve vertex
	ny /= trial_dist;
	d /= trial_dist;

	return Vector(nx,ny,d);
}

void CacheOptimizedTriangle::ChangeIntoIntersectionFormat(void)
{
	// lose the vertices and use edge equations instead

	// grab the whole original triangle to we don't overwrite it
	TriGeometryData_t srcTri = m_Data.m_GeometryData;

	m_Data.m_IntersectData.m_nFlags = srcTri.m_nFlags;
	m_Data.m_IntersectData.m_nTriangleID = srcTri.m_nTriangleID;

	Vector p1 = srcTri.Vertex( 0 );
	Vector p2 = srcTri.Vertex( 1 );
	Vector p3 = srcTri.Vertex( 2 );

	Vector e1 = p2 - p1;
	Vector e2 = p3 - p1;

	Vector N = e1.Cross( e2 );
	N.NormalizeInPlace();
	// now, determine which axis to drop
	int drop_axis = 0;
	for(int c=1 ; c<3 ; c++)
		if ( fabs(N[c]) > fabs( N[drop_axis] ) )
			drop_axis = c;

	m_Data.m_IntersectData.m_flD = N.Dot( p1 );
	m_Data.m_IntersectData.m_flNx = N.x;
	m_Data.m_IntersectData.m_flNy = N.y;
	m_Data.m_IntersectData.m_flNz = N.z;

	// decide which axes to keep
	int nCoordSelect0 = ( drop_axis + 1 ) % 3;
	int nCoordSelect1 = ( drop_axis + 2 ) % 3;

	m_Data.m_IntersectData.m_nCoordSelect0 = nCoordSelect0;
	m_Data.m_IntersectData.m_nCoordSelect1 = nCoordSelect1;


	Vector edge1 = GetEdgeEquation( p1, p2, nCoordSelect0, nCoordSelect1, p3 );
	m_Data.m_IntersectData.m_ProjectedEdgeEquations[0] = edge1.x;
	m_Data.m_IntersectData.m_ProjectedEdgeEquations[1] = edge1.y;
	m_Data.m_IntersectData.m_ProjectedEdgeEquations[2] = edge1.z;

	Vector edge2 = GetEdgeEquation( p2, p3, nCoordSelect0, nCoordSelect1, p1 );
	m_Data.m_IntersectData.m_ProjectedEdgeEquations[3] = edge2.x;
	m_Data.m_IntersectData.m_ProjectedEdgeEquations[4] = edge2.y;
	m_Data.m_IntersectData.m_ProjectedEdgeEquations[5] = edge2.z;


}

int n_intersection_calculations=0;

int CacheOptimizedTriangle::ClassifyAgainstAxisSplit(int split_plane, float split_value)
{
	// classify a triangle against an axis-aligned plane
	float minc=Vertex(0)[split_plane];
	float maxc=minc;
	for(int v=1;v<3;v++)
	{
		minc=min(minc,Vertex(v)[split_plane]);
		maxc=max(maxc,Vertex(v)[split_plane]);
	}

	if (minc>=split_value)
		return PLANECHECK_POSITIVE;
	if (maxc<=split_value)
		return PLANECHECK_NEGATIVE;
	if (minc==maxc)
		return PLANECHECK_POSITIVE;
	return PLANECHECK_STRADDLING;
}

#define MAILBOX_HASH_SIZE 256
#define MAX_TREE_DEPTH 21
#define MAX_NODE_STACK_LEN (40*MAX_TREE_DEPTH)

struct NodeToVisit {
	CacheOptimizedKDNode const *node;
	fltx4 TMin;
	fltx4 TMax;
};


static fltx4 FourEpsilons={1.0e-10,1.0e-10,1.0e-10,1.0e-10};
static fltx4 FourZeros={1.0e-10,1.0e-10,1.0e-10,1.0e-10};
static fltx4 FourNegativeEpsilons={-1.0e-10,-1.0e-10,-1.0e-10,-1.0e-10};

static float BoxSurfaceArea(Vector const &boxmin, Vector const &boxmax)
{
	Vector boxdim=boxmax-boxmin;
	return 2.0*((boxdim[0]*boxdim[2])+(boxdim[0]*boxdim[1])+(boxdim[1]*boxdim[2]));
}

void RayTracingEnvironment::Trace4Rays(const FourRays &rays, fltx4 TMin, fltx4 TMax,
									   RayTracingResult *rslt_out,
									   int32 skip_id, ITransparentTriangleCallback *pCallback)
{
	int msk=rays.CalculateDirectionSignMask();
	if (msk!=-1)
		Trace4Rays(rays,TMin,TMax,msk,rslt_out,skip_id, pCallback);
	else
	{
		// sucky case - can't trace 4 rays at once. in the worst case, need to trace all 4
		// separately, but usually we will still get 2x, Since our tracer only does 4 at a
		// time, we will have to cover up the undesired rays with the desired ray

		//!! speed!! there is room for some sse-ization here
		FourRays tmprays;
		tmprays.origin=rays.origin;

		uint8 need_trace[4]={1,1,1,1};
		for(int try_trace=0;try_trace<4;try_trace++)
		{
			if (need_trace[try_trace])
			{
				need_trace[try_trace]=2;			// going to trace it
				// replicate the ray being traced into all 4 rays
				tmprays.direction.x=ReplicateX4(rays.direction.X(try_trace));
				tmprays.direction.y=ReplicateX4(rays.direction.Y(try_trace));
				tmprays.direction.z=ReplicateX4(rays.direction.Z(try_trace));
				// now, see if any of the other remaining rays can be handled at the same time.
				for(int try2=try_trace+1;try2<4;try2++)
					if (need_trace[try2])
					{
						if (
							SameSign(rays.direction.X(try2),
									 rays.direction.X(try_trace)) &&
							SameSign(rays.direction.Y(try2),
									 rays.direction.Y(try_trace)) &&
							SameSign(rays.direction.Z(try2),
									 rays.direction.Z(try_trace)))
						{
							need_trace[try2]=2;
							tmprays.direction.X(try2) = rays.direction.X(try2);
							tmprays.direction.Y(try2) = rays.direction.Y(try2);
							tmprays.direction.Z(try2) = rays.direction.Z(try2);
						}
					}
				// ok, now trace between 1 and 3 rays, and output the results
				RayTracingResult tmpresults;
				msk=tmprays.CalculateDirectionSignMask();
				assert(msk!=-1);
				Trace4Rays(tmprays,TMin,TMax,msk,&tmpresults,skip_id, pCallback);
				// now, move results to proper place
				for(int i=0;i<4;i++)
					if (need_trace[i]==2)
					{
						need_trace[i]=0;
						rslt_out->HitIds[i]=tmpresults.HitIds[i];
						SubFloat(rslt_out->HitDistance, i) = SubFloat(tmpresults.HitDistance, i);
						rslt_out->surface_normal.X(i) = tmpresults.surface_normal.X(i);
						rslt_out->surface_normal.Y(i) = tmpresults.surface_normal.Y(i);
						rslt_out->surface_normal.Z(i) = tmpresults.surface_normal.Z(i);
					}
				
			}
		}
	}
}


void RayTracingEnvironment::Trace4Rays(const FourRays &rays, fltx4 TMin, fltx4 TMax,
									   int DirectionSignMask, RayTracingResult *rslt_out,
									   int32 skip_id, ITransparentTriangleCallback *pCallback)
{
	rays.Check();

	memset(rslt_out->HitIds,0xff,sizeof(rslt_out->HitIds));

	rslt_out->HitDistance=ReplicateX4(1.0e23);

	rslt_out->surface_normal.DuplicateVector(Vector(0.,0.,0.));
	FourVectors OneOverRayDir=rays.direction;
	OneOverRayDir.MakeReciprocalSaturate();
	
	// now, clip rays against bounding box
	for(int c=0;c<3;c++)
	{
		fltx4 isect_min_t=
			MulSIMD(SubSIMD(ReplicateX4(m_MinBound[c]),rays.origin[c]),OneOverRayDir[c]);
		fltx4 isect_max_t=
			MulSIMD(SubSIMD(ReplicateX4(m_MaxBound[c]),rays.origin[c]),OneOverRayDir[c]);
		TMin=MaxSIMD(TMin,MinSIMD(isect_min_t,isect_max_t));
		TMax=MinSIMD(TMax,MaxSIMD(isect_min_t,isect_max_t));
	}
	fltx4 active=CmpLeSIMD(TMin,TMax);					// mask of which rays are active
	if (! IsAnyNegative(active) )
		return;												// missed bounding box

	int32 mailboxids[MAILBOX_HASH_SIZE];					// used to avoid redundant triangle tests
	memset(mailboxids,0xff,sizeof(mailboxids));				// !!speed!! keep around?

	int front_idx[3],back_idx[3];							// based on ray direction, whether to
															// visit left or right node first

	if (DirectionSignMask & 1)
	{
		back_idx[0]=0;
		front_idx[0]=1;
	}
		else
	{
		back_idx[0]=1;
		front_idx[0]=0;
	}
	if (DirectionSignMask & 2)
	{
		back_idx[1]=0;
		front_idx[1]=1;
	}
	else
	{
		back_idx[1]=1;
		front_idx[1]=0;
	}
	if (DirectionSignMask & 4)
	{
		back_idx[2]=0;
		front_idx[2]=1;
	}
	else
	{
		back_idx[2]=1;
		front_idx[2]=0;
	}
		
	NodeToVisit NodeQueue[MAX_NODE_STACK_LEN];
	CacheOptimizedKDNode const *CurNode=&(OptimizedKDTree[0]);
	NodeToVisit *stack_ptr=&NodeQueue[MAX_NODE_STACK_LEN];
	while(1)
	{
		while (CurNode->NodeType() != KDNODE_STATE_LEAF)		// traverse until next leaf
		{	   
			int split_plane_number=CurNode->NodeType();
			CacheOptimizedKDNode const *FrontChild=&(OptimizedKDTree[CurNode->LeftChild()]);
			
			fltx4 dist_to_sep_plane=						// dist=(split-org)/dir
				MulSIMD(
					SubSIMD(ReplicateX4(CurNode->SplittingPlaneValue),
							   rays.origin[split_plane_number]),OneOverRayDir[split_plane_number]);
			active=CmpLeSIMD(TMin,TMax);			// mask of which rays are active

			// now, decide how to traverse children. can either do front,back, or do front and push
			// back.
			fltx4 hits_front=AndSIMD(active,CmpGeSIMD(dist_to_sep_plane,TMin));
			if (! IsAnyNegative(hits_front))
			{
				// missed the front. only traverse back
				//printf("only visit back %d\n",CurNode->LeftChild()+back_idx[split_plane_number]);
				CurNode=FrontChild+back_idx[split_plane_number];
				TMin=MaxSIMD(TMin, dist_to_sep_plane);

			}
			else
			{
				fltx4 hits_back=AndSIMD(active,CmpLeSIMD(dist_to_sep_plane,TMax));
				if (! IsAnyNegative(hits_back) )
				{
					// missed the back - only need to traverse front node
					//printf("only visit front %d\n",CurNode->LeftChild()+front_idx[split_plane_number]);
					CurNode=FrontChild+front_idx[split_plane_number];
					TMax=MinSIMD(TMax, dist_to_sep_plane);
				}
				else
				{
					// at least some rays hit both nodes.
					// must push far, traverse near
 					//printf("visit %d,%d\n",CurNode->LeftChild()+front_idx[split_plane_number],
 					//	   CurNode->LeftChild()+back_idx[split_plane_number]);
					assert(stack_ptr>NodeQueue);
					--stack_ptr;
					stack_ptr->node=FrontChild+back_idx[split_plane_number];
					stack_ptr->TMin=MaxSIMD(TMin,dist_to_sep_plane);
					stack_ptr->TMax=TMax;
					CurNode=FrontChild+front_idx[split_plane_number];
					TMax=MinSIMD(TMax,dist_to_sep_plane);
				}
			}
		}
		// hit a leaf! must do intersection check
		int ntris=CurNode->NumberOfTrianglesInLeaf();
		if (ntris)
		{
			int32 const *tlist=&(TriangleIndexList[CurNode->TriangleIndexStart()]);
			do
			{
				int tnum=*(tlist++);
				//printf("try tri %d\n",tnum);
				// check mailbox
				int mbox_slot=tnum & (MAILBOX_HASH_SIZE-1);
				TriIntersectData_t const *tri = &( OptimizedTriangleList[tnum].m_Data.m_IntersectData );
				if ( ( mailboxids[mbox_slot] != tnum ) && ( tri->m_nTriangleID != skip_id ) )
				{
					n_intersection_calculations++;
					mailboxids[mbox_slot] = tnum;
					// compute plane intersection


					FourVectors N;
					N.x = ReplicateX4( tri->m_flNx );
					N.y = ReplicateX4( tri->m_flNy );
					N.z = ReplicateX4( tri->m_flNz );

					fltx4 DDotN = rays.direction * N;
					// mask off zero or near zero (ray parallel to surface)
					fltx4 did_hit = OrSIMD( CmpGtSIMD( DDotN,FourEpsilons ),
											CmpLtSIMD( DDotN, FourNegativeEpsilons ) );

					fltx4 numerator=SubSIMD( ReplicateX4( tri->m_flD ), rays.origin * N );

					fltx4 isect_t=DivSIMD( numerator,DDotN );
					// now, we have the distance to the plane. lets update our mask
					did_hit = AndSIMD( did_hit, CmpGtSIMD( isect_t, FourZeros ) );
					//did_hit=AndSIMD(did_hit,CmpLtSIMD(isect_t,TMax));
					did_hit = AndSIMD( did_hit, CmpLtSIMD( isect_t, rslt_out->HitDistance ) );

					if ( ! IsAnyNegative( did_hit ) )
						continue;

					// now, check 3 edges
					fltx4 hitc1 = AddSIMD( rays.origin[tri->m_nCoordSelect0],
										MulSIMD( isect_t, rays.direction[ tri->m_nCoordSelect0] ) );
					fltx4 hitc2 = AddSIMD( rays.origin[tri->m_nCoordSelect1],
										   MulSIMD( isect_t, rays.direction[tri->m_nCoordSelect1] ) );
					
					// do barycentric coordinate check
					fltx4 B0 = MulSIMD( ReplicateX4( tri->m_ProjectedEdgeEquations[0] ), hitc1 );

					B0 = AddSIMD(
						B0,
						MulSIMD( ReplicateX4( tri->m_ProjectedEdgeEquations[1] ), hitc2 ) );
					B0 = AddSIMD(
						B0, ReplicateX4( tri->m_ProjectedEdgeEquations[2] ) );

					did_hit = AndSIMD( did_hit, CmpGeSIMD( B0, FourZeros ) );

					fltx4 B1 = MulSIMD( ReplicateX4( tri->m_ProjectedEdgeEquations[3] ), hitc1 );
					B1 = AddSIMD(
						B1,
						MulSIMD( ReplicateX4( tri->m_ProjectedEdgeEquations[4]), hitc2 ) );

					B1 = AddSIMD(
						B1, ReplicateX4( tri->m_ProjectedEdgeEquations[5] ) );
					
					did_hit = AndSIMD( did_hit, CmpGeSIMD( B1, FourZeros ) );

					fltx4 B2 = AddSIMD( B1, B0 );
					did_hit = AndSIMD( did_hit, CmpLeSIMD( B2, Four_Ones ) );

					if ( ! IsAnyNegative( did_hit ) )
						continue;

					// if the triangle is transparent
					if ( tri->m_nFlags & FCACHETRI_TRANSPARENT )
					{
						if ( pCallback )
						{
							// assuming a triangle indexed as v0, v1, v2
							// the projected edge equations are set up such that the vert opposite the first
							// equation is v2, and the vert opposite the second equation is v0
							// Therefore we pass them back in 1, 2, 0 order
							// Also B2 is currently B1 + B0 and needs to be 1 - (B1+B0) in order to be a real
							// barycentric coordinate.  Compute that now and pass it to the callback
							fltx4 b2 = SubSIMD( Four_Ones, B2 );
							if ( pCallback->VisitTriangle_ShouldContinue( *tri, rays, &did_hit, &B1, &b2, &B0, tnum ) )
							{
								did_hit = Four_Zeros;
							}
						}
					}
					// now, set the hit_id and closest_hit fields for any enabled rays
					fltx4 replicated_n = ReplicateIX4(tnum);
					StoreAlignedSIMD((float *) rslt_out->HitIds,
								 OrSIMD(AndSIMD(replicated_n,did_hit),
										   AndNotSIMD(did_hit,LoadAlignedSIMD(
															 (float *) rslt_out->HitIds))));
					rslt_out->HitDistance=OrSIMD(AndSIMD(isect_t,did_hit),
									 AndNotSIMD(did_hit,rslt_out->HitDistance));

					rslt_out->surface_normal.x=OrSIMD(
						AndSIMD(N.x,did_hit),
						AndNotSIMD(did_hit,rslt_out->surface_normal.x));
					rslt_out->surface_normal.y=OrSIMD(
						AndSIMD(N.y,did_hit),
						AndNotSIMD(did_hit,rslt_out->surface_normal.y));
					rslt_out->surface_normal.z=OrSIMD(
						AndSIMD(N.z,did_hit),
						AndNotSIMD(did_hit,rslt_out->surface_normal.z));
					
				}
			} while (--ntris);
			// now, check if all rays have terminated
			fltx4 raydone=CmpLeSIMD(TMax,rslt_out->HitDistance);
			if (! IsAnyNegative(raydone))
			{
				return;
			}
		}
		
 		if (stack_ptr==&NodeQueue[MAX_NODE_STACK_LEN])
		{
			return;
		}
		// pop stack!
		CurNode=stack_ptr->node;
		TMin=stack_ptr->TMin;
		TMax=stack_ptr->TMax;
		stack_ptr++;
	}
}


int RayTracingEnvironment::MakeLeafNode(int first_tri, int last_tri)
{
	CacheOptimizedKDNode ret;
	ret.Children=KDNODE_STATE_LEAF+(TriangleIndexList.Count()<<2);
	ret.SetNumberOfTrianglesInLeafNode(1+(last_tri-first_tri));
	for(int tnum=first_tri;tnum<=last_tri;tnum++)
		TriangleIndexList.AddToTail(tnum);
	OptimizedKDTree.AddToTail(ret);
	return OptimizedKDTree.Count()-1;
}


void RayTracingEnvironment::CalculateTriangleListBounds(int32 const *tris,int ntris,
														Vector &minout, Vector &maxout)
{
	minout = Vector( 1.0e23, 1.0e23, 1.0e23);
	maxout = Vector( -1.0e23, -1.0e23, -1.0e23);
	for(int i=0; i<ntris; i++)
	{
		CacheOptimizedTriangle const &tri=OptimizedTriangleList[tris[i]];
		for(int v=0; v<3; v++)
			for(int c=0; c<3; c++)
			{
				minout[c]=min(minout[c],tri.Vertex(v)[c]);
							  maxout[c]=max(maxout[c],tri.Vertex(v)[c]);
			}
	}
}


// Both the "quick" and regular kd tree building algorithms here use the "surface area heuristic":
// the relative probability of hitting the "left" subvolume (Vl) from a split is equal to that
// subvolume's surface area divided by its parent's surface area (Vp) : P(Vl | V)=SA(Vl)/SA(Vp).
// The same holds for the right subvolume, Vp. Nl is the number of triangles in the left volume,
// and Nr in the right volume. if Ct is the cost of traversing one tree node, and Ci is the cost of
// intersection with the primitive, than the cost of splitting is estimated as:
//
//    Ct+Ci*((SA(Vl)/SA(V))*Nl+(SA(Vr)/SA(V)*Nr)).
// and the cost of not splitting is
//    Ci*N
//
//  This both provides a metric to minimize when computing how and where to split, and also a
//  termination criterion.
//
// the "quick" method just splits down the middle, while the slow method splits at the best
// discontinuity of the cost formula. The quick method splits along the longest axis ; the 
// regular algorithm tries all 3 to find which one results in the minimum cost
// 
// both methods use the additional optimization of "growing" empty nodes - if the split results in
// one side being devoid of triangles, the empty side is "grown" as much as possible.
//

#define COST_OF_TRAVERSAL 75								// approximate #operations
#define COST_OF_INTERSECTION 167							// approximate #operations


float RayTracingEnvironment::CalculateCostsOfSplit(
	int split_plane,int32 const *tri_list,int ntris,
	Vector MinBound,Vector MaxBound, float &split_value,
	int &nleft, int &nright, int &nboth)
{
	// determine the costs of splitting on a given axis, and label triangles with respect to
	// that axis by storing the value in coordselect0. It will also return the number of
	// tris in the left, right, and nboth groups, in order to facilitate memory
	nleft=nboth=nright=0;
	
	// now, label each triangle. Since we have not converted the triangles into
	// intersection fromat yet, we can use the CoordSelect0 field of each as a temp.
	nleft=0;
	nright=0;
	nboth=0;
	float min_coord=1.0e23,max_coord=-1.0e23;

	for(int t=0;t<ntris;t++)
	{
		CacheOptimizedTriangle &tri=OptimizedTriangleList[tri_list[t]];
		// determine max and min coordinate values for later optimization
		for(int v=0;v<3;v++)
		{
			min_coord = min( min_coord, tri.Vertex(v)[split_plane] );
			max_coord = max( max_coord, tri.Vertex(v)[split_plane] );
		}
		switch(tri.ClassifyAgainstAxisSplit(split_plane,split_value))
		{
			case PLANECHECK_NEGATIVE:
				nleft++;
				tri.m_Data.m_GeometryData.m_nTmpData0 = PLANECHECK_NEGATIVE;
				break;

			case PLANECHECK_POSITIVE:
				nright++;
				tri.m_Data.m_GeometryData.m_nTmpData0 = PLANECHECK_POSITIVE;
				break;

			case PLANECHECK_STRADDLING:
				nboth++;
				tri.m_Data.m_GeometryData.m_nTmpData0 = PLANECHECK_STRADDLING;
				break;
		}
	}
	// now, if the split resulted in one half being empty, "grow" the empty half
	if (nleft && (nboth==0) && (nright==0))
		split_value=max_coord;
	if (nright && (nboth==0) && (nleft==0))
		split_value=min_coord;

	// now, perform surface area/cost check to determine whether this split was worth it
	Vector LeftMins=MinBound;
	Vector LeftMaxes=MaxBound;
	Vector RightMins=MinBound;
	Vector RightMaxes=MaxBound;
	LeftMaxes[split_plane]=split_value;
	RightMins[split_plane]=split_value;
	float SA_L=BoxSurfaceArea(LeftMins,LeftMaxes);
	float SA_R=BoxSurfaceArea(RightMins,RightMaxes);
	float ISA=1.0/BoxSurfaceArea(MinBound,MaxBound);
	float cost_of_split=COST_OF_TRAVERSAL+COST_OF_INTERSECTION*(nboth+
		(SA_L*ISA*(nleft))+(SA_R*ISA*(nright)));
	return cost_of_split;
}


#define NEVER_SPLIT 0

void RayTracingEnvironment::RefineNode(int node_number,int32 const *tri_list,int ntris,
									   Vector MinBound,Vector MaxBound, int depth)
{
	if (ntris<3)											// never split empty lists
	{
		// no point in continuing
		OptimizedKDTree[node_number].Children=KDNODE_STATE_LEAF+(TriangleIndexList.Count()<<2);
		OptimizedKDTree[node_number].SetNumberOfTrianglesInLeafNode(ntris);

#ifdef DEBUG_RAYTRACE
		OptimizedKDTree[node_number].vecMins = MinBound;
		OptimizedKDTree[node_number].vecMaxs = MaxBound;
#endif

		for(int t=0;t<ntris;t++)
			TriangleIndexList.AddToTail(tri_list[t]);
		return;
	}

	float best_cost=1.0e23;
	int best_nleft=0,best_nright=0,best_nboth=0;
	float best_splitvalue=0;
	int split_plane=0;

	int tri_skip=1+(ntris/10);								// don't try all trinagles as split
															// points when there are a lot of them
	for(int axis=0;axis<3;axis++)
	{
		for(int ts=-1;ts<ntris;ts+=tri_skip)
		{
			for(int tv=0;tv<3;tv++)
			{
				int trial_nleft,trial_nright,trial_nboth;
				float trial_splitvalue;
				if (ts==-1)
					trial_splitvalue=0.5*(MinBound[axis]+MaxBound[axis]);
				else
				{
					// else, split at the triangle vertex if possible
					CacheOptimizedTriangle &tri=OptimizedTriangleList[tri_list[ts]];
					trial_splitvalue = tri.Vertex(tv)[axis];
					if ((trial_splitvalue>MaxBound[axis]) || (trial_splitvalue<MinBound[axis]))
						continue;							// don't try this vertex - not inside
					
				}
//				printf("ts=%d tv=%d tp=%f\n",ts,tv,trial_splitvalue);
				float trial_cost=
					CalculateCostsOfSplit(axis,tri_list,ntris,MinBound,MaxBound,trial_splitvalue,
										  trial_nleft,trial_nright, trial_nboth);
// 				printf("try %d cost=%f nl=%d nr=%d nb=%d sp=%f\n",axis,trial_cost,trial_nleft,trial_nright, trial_nboth,
// 					   trial_splitvalue);
				if (trial_cost<best_cost)
				{
					split_plane=axis;
					best_cost=trial_cost;
					best_nleft=trial_nleft;
					best_nright=trial_nright;
					best_nboth=trial_nboth;
					best_splitvalue=trial_splitvalue;
					// save away the axis classification of each triangle
					for(int t=0 ; t < ntris; t++)
					{
						CacheOptimizedTriangle &tri=OptimizedTriangleList[tri_list[t]];
						tri.m_Data.m_GeometryData.m_nTmpData1 = tri.m_Data.m_GeometryData.m_nTmpData0;
					}
				}
				if (ts==-1)
					break;
			}
		}

	}
	float cost_of_no_split=COST_OF_INTERSECTION*ntris;
	if ( (cost_of_no_split<=best_cost) || NEVER_SPLIT || (depth>MAX_TREE_DEPTH))
	{
		// no benefit to splitting. just make this a leaf node
		OptimizedKDTree[node_number].Children=KDNODE_STATE_LEAF+(TriangleIndexList.Count()<<2);
		OptimizedKDTree[node_number].SetNumberOfTrianglesInLeafNode(ntris);
#ifdef DEBUG_RAYTRACE
		OptimizedKDTree[node_number].vecMins = MinBound;
		OptimizedKDTree[node_number].vecMaxs = MaxBound;
#endif
		for(int t=0;t<ntris;t++)
			TriangleIndexList.AddToTail(tri_list[t]);
	}
	else
	{
// 		printf("best split was %d at %f (mid=%f,n=%d, sk=%d)\n",split_plane,best_splitvalue,
// 			   0.5*(MinBound[split_plane]+MaxBound[split_plane]),ntris,tri_skip);
		// its worth splitting!
		// we will achieve the splitting without sorting by using a selection algorithm.
		int32 *new_triangle_list;
		new_triangle_list=new int32[ntris];

		// now, perform surface area/cost check to determine whether this split was worth it
		Vector LeftMins=MinBound;
		Vector LeftMaxes=MaxBound;
		Vector RightMins=MinBound;
		Vector RightMaxes=MaxBound;
		LeftMaxes[split_plane]=best_splitvalue;
		RightMins[split_plane]=best_splitvalue;
		
		int n_left_output=0;
		int n_both_output=0;
		int n_right_output=0;
		for(int t=0;t<ntris;t++)
		{
			CacheOptimizedTriangle &tri=OptimizedTriangleList[tri_list[t]];
			switch( tri.m_Data.m_GeometryData.m_nTmpData1 )
			{
				case PLANECHECK_NEGATIVE:
//					printf("%d goes left\n",t);
					new_triangle_list[n_left_output++]=tri_list[t];
					break;
				case PLANECHECK_POSITIVE:
					n_right_output++;
//					printf("%d goes right\n",t);
					new_triangle_list[ntris-n_right_output]=tri_list[t];
					break;
				case PLANECHECK_STRADDLING:
//					printf("%d goes both\n",t);
					new_triangle_list[best_nleft+n_both_output]=tri_list[t];
					n_both_output++;
					break;

					
			}
		}
		int left_child=OptimizedKDTree.Count();
		int right_child=left_child+1;
// 		printf("node %d split on axis %d at %f, nl=%d nr=%d nb=%d lc=%d rc=%d\n",node_number,
// 			   split_plane,best_splitvalue,best_nleft,best_nright,best_nboth,
// 			   left_child,right_child);
		OptimizedKDTree[node_number].Children=split_plane+(left_child<<2);
		OptimizedKDTree[node_number].SplittingPlaneValue=best_splitvalue;
#ifdef DEBUG_RAYTRACE
		OptimizedKDTree[node_number].vecMins = MinBound;
		OptimizedKDTree[node_number].vecMaxs = MaxBound;
#endif
		CacheOptimizedKDNode newnode;
		OptimizedKDTree.AddToTail(newnode);
		OptimizedKDTree.AddToTail(newnode);
		// now, recurse!
		if ( (ntris<20) && ((best_nleft==0) || (best_nright==0)) )
			depth+=100;
		RefineNode(left_child,new_triangle_list,best_nleft+best_nboth,LeftMins,LeftMaxes,depth+1);
		RefineNode(right_child,new_triangle_list+best_nleft,best_nright+best_nboth,
				   RightMins,RightMaxes,depth+1);
		delete[] new_triangle_list;
	}	
}


void RayTracingEnvironment::SetupAccelerationStructure(void)
{
	CacheOptimizedKDNode root;
	OptimizedKDTree.AddToTail(root);
	int32 *root_triangle_list=new int32[OptimizedTriangleList.Count()];
	for(int t=0;t<OptimizedTriangleList.Count();t++)
		root_triangle_list[t]=t;
	CalculateTriangleListBounds(root_triangle_list,OptimizedTriangleList.Count(),m_MinBound,
								m_MaxBound);
	RefineNode(0,root_triangle_list,OptimizedTriangleList.Count(),m_MinBound,m_MaxBound,0);
	delete[] root_triangle_list;

	// now, convert all triangles to "intersection format"
	for(int i=0;i<OptimizedTriangleList.Count();i++)
		OptimizedTriangleList[i].ChangeIntoIntersectionFormat();
}



void RayTracingEnvironment::AddInfinitePointLight(Vector position, Vector intensity)
{
	LightDesc_t mylight(position,intensity);
	LightList.AddToTail(mylight);
	
}