/* Compute form-factors from the shooting patch to every elements */
static void ComputeFormfactors(unsigned long shootPatch)
{
unsigned long i;
TVector3f up[5];
TPoint3f lookat[5];
TPoint3f center;
TVector3f normal, tangentU, tangentV, vec;
int face;
double norm;
TPatch* sp;
double* fp;
TElement* ep;
/* get the center of shootPatch */
sp = &(params->patches[shootPatch]);
center = sp->center;
normal = sp->normal;
/* rotate the hemi-cube along the normal axis of the patch randomly */
/* this will reduce the hemi-cube aliasing artifacts */
do {
vec.x = RandomFloat;
vec.y = RandomFloat;
vec.z = RandomFloat;
/* get a tangent vector */
CrossVector(tangentU, normal, vec);
NormalizeVector(norm, tangentU);
} while (norm==0); /* bad choice of the random vector */
/* compute tangentV */
CrossVector(tangentV, normal, tangentU);
/* assign the lookats and ups for each hemicube face */
AddVector(lookat[0], center, normal);
up[0] = tangentU;
AddVector(lookat[1], center, tangentU);
up[1] = normal;
AddVector(lookat[2], center, tangentV);
up[2] = normal;
SubVector(lookat[3], center, tangentU);
up[3] = normal;
SubVector(lookat[4], center, tangentV);
up[4] = normal;
/* position the hemicube slightly above the center of the shooting patch */
ScaleVector(normal, params->worldSize*0.0001);
AddVector(hemicube.view.camera, center, normal);
/* clear the formfactors */
fp = formfactors;
for (i=params->nElements; i--; fp++)
*fp = 0.0;
for (face=0; face < 5; face++)
{
hemicube.view.lookat = lookat[face];
hemicube.view.up = up[face];
/* draw elements */
BeginDraw(&(hemicube.view), kBackgroundItem);
for (i=0; i< params->nElements; i++)
DrawElement(¶ms->elements[i], i);
/* color element i with its index */
EndDraw();
/* get formfactors */
if (face==0)
SumFactors(formfactors, hemicube.view.xRes, hemicube.view.yRes,
hemicube.view.buffer, hemicube.topFactors);
else
SumFactors(formfactors, hemicube.view.xRes, hemicube.view.yRes/2,
hemicube.view.buffer, hemicube.sideFactors);
}
/* compute reciprocal form-factors */
ep = params->elements;
fp = formfactors;
for (i=params->nElements; i--; ep++, fp++)
{
*fp *= sp->area / ep->area;
/* This is a potential source of hemi-cube aliasing */
/* To do this right, we need to subdivide the shooting patch
and reshoot. For now we just clip it to unity */
if ((*fp) > 1.0) *fp = 1.0;
}
}
/* Compute form-factors from the shooting patch to every elements */
static void ComputeFormfactors(unsigned long shootPatch)
{
unsigned long i;
TVector3f up[5];
TPoint3f lookat[5];
TPoint3f center;
TVector3f normal, tangentU, tangentV, vec;
int face;
double norm;
TPatch* sp;
double* fp;
TElement* ep;
double plane_eq[4];
/* get the center of shootPatch */
sp = &(params->patches[shootPatch]);
center = sp->center;
normal = sp->normal;
plane_eq[0] = (double)normal.x;
plane_eq[1] = (double)normal.y;
plane_eq[2] = (double)normal.z;
plane_eq[3] = (double)-(normal.x*center.x + normal.y*center.y +
normal.z*center.z);
/* rotate the hemi-cube along the normal axis of the patch randomly */
/* this will reduce the hemi-cube aliasing artifacts */
do {
vec.x = RandomFloat;
vec.y = RandomFloat;
vec.z = RandomFloat;
/* get a tangent vector */
CrossVector(tangentU, normal, vec);
NormalizeVector(norm, tangentU);
} while (norm==0); /* bad choice of the random vector */
/* compute tangentV */
CrossVector(tangentV, normal, tangentU);
/* assign the lookats and ups for each hemicube face */
AddVector(lookat[0], center, normal);
up[0] = tangentU;
AddVector(lookat[1], center, tangentU);
up[1] = normal;
AddVector(lookat[2], center, tangentV);
up[2] = normal;
SubVector(lookat[3], center, tangentU);
up[3] = normal;
SubVector(lookat[4], center, tangentV);
up[4] = normal;
/* position the hemicube slightly above the center of the shooting patch */
ScaleVector(normal, params->worldSize*0.00000001);
AddVector(hemicube.view.camera, center, normal);
/* clear the formfactors */
fp = formfactors;
for (i=params->nElements; i--; fp++)
*fp = 0.0;
for (face=0; face < 5; face++)
{
hemicube.view.lookat = lookat[face];
hemicube.view.up = up[face];
/* draw elements */
if (bits_for_RGB == 24) { /* a 24-bit display */
BeginHCDraw(&(hemicube.view), kBackgroundItem, plane_eq);
for (i=0; i< params->nElements; i++)
DrawHCElement(¶ms->elements[i], i);
/* color element i with its index */
EndHCDraw(&(hemicube.view));
} else if (bits_for_RGB == 8) { /* an 8-bit display */
/* this is a quick hack to make it work for 8-bit
displays maybe a better way could be found ??? */
part_of_id = 1; /* processing first half of polygon ids */
BeginHCDraw(&(hemicube.view), 255, plane_eq);
for (i=0; i< params->nElements; i++)
DrawHCElement(¶ms->elements[i], i);
/* color element i with its index */
EndHCDraw(&(hemicube.view));
part_of_id = 2; /* second half of polygon ids */
BeginHCDraw(&(hemicube.view), 255, plane_eq);
for (i=0; i< params->nElements; i++)
DrawHCElement(¶ms->elements[i], i);
/* color element i with its index */
EndHCDraw(&(hemicube.view));
} else {
printf("Unexpected bits per RGB colour, exiting");
//exit(0);
}
/* get formfactors */
if (face==0)
SumFactors(formfactors, hemicube.view.xRes, hemicube.view.yRes,
hemicube.view.buffer, hemicube.topFactors,0);
else
SumFactors(formfactors, hemicube.view.xRes, hemicube.view.yRes,
hemicube.view.buffer, hemicube.sideFactors,
hemicube.view.yRes/2);
}
/* compute reciprocal form-factors */
ep = params->elements;
fp = formfactors;
for (i=params->nElements; i--; ep++, fp++)
{
*fp *= sp->area / ep->area;
/* This is a potential source of hemi-cube aliasing */
/* To do this right, we need to subdivide the shooting patch
and reshoot. For now we just clip it to unity */
if ((*fp) > 1.0) *fp = 1.0;
}
}
