// Foley & vanDam: Computer Graphics: Principles and Practice,
// 2nd Ed. pp 756ff.
Point3 SContext::RefractVector(float ior)
{
Point3 N = Normal();
float VN,nur,k;
VN = DotProd(-viewDir,N);
if (backFace) nur = ior;
else nur = (ior!=0.0f) ? 1.0f/ior: 1.0f;
k = 1.0f-nur*nur*(1.0f-VN*VN);
if (k<=0.0f) {
// Total internal reflection:
return ReflectVector();
}
else {
return (nur*VN-(float)sqrt(k))*N + nur*viewDir;
}
}
static void TraceLine( VECTOR *LinP, VECTOR *LinD, VECTOR *Color, int reccount )
{
VECTOR Pnt, Norm, LDir, NewDir, NewDir2, TmpCol, TmpCol2;
VECTOR TmpPnt, TmpNorm, D;
double t, A, cosfi;
TEXTURE *txt, *tmptxt;
int i, shadowcount, usedist;
Color->x = Color->y = Color->z = 0.0;
if( reccount > 0 ) {
/* Only use distributed tracing in higher nodes of the recursion tree */
usedist = ( (MAXREC-reccount) < DISTLEVELS ) ? 1 : 0;
/* Try intersection with objects */
t = IntersectObjs( LinP, LinD, &Pnt, &Norm, &txt );
/* Get light-intensity in intersection-point (store in cosfi) */
if( t > EPSILON ) {
LDir.x = Lightpos.x-Pnt.x; /* Get line to light from surface */
LDir.y = Lightpos.y-Pnt.y;
LDir.z = Lightpos.z-Pnt.z;
cosfi = LDir.x*Norm.x + LDir.y*Norm.y + LDir.z*Norm.z;
if(cosfi > 0.0) { /* If angle between lightline and normal < PI/2 */
shadowcount = 0;
if( usedist ) {
A = Lightr / VectorLength( &LDir );
for( i = 0; i < DISTRIB; i++ ) {
DistribVector( &D, &LDir, A, A );
NewDir = LDir;
NewDir.x += D.x; NewDir.y += D.y; NewDir.z += D.z;
/* Check for shadows (ignore hit info, may be used though) */
t = IntersectObjs( &Pnt, &NewDir, &TmpPnt, &TmpNorm, &tmptxt );
if( ( t < EPSILON ) || ( t > 1.0 ) ) shadowcount++;
}
} else {
t = IntersectObjs( &Pnt, &LDir, &TmpPnt, &TmpNorm, &tmptxt );
if( ( t < EPSILON ) || ( t > 1.0 ) ) shadowcount = DISTRIB;
}
if( shadowcount > 0 ) {
A = Norm.x*Norm.x + Norm.y*Norm.y + Norm.z*Norm.z;
A *= LDir.x*LDir.x + LDir.y*LDir.y + LDir.z*LDir.z;
cosfi = (cosfi/sqrt(A))*txt->diffuse*(double)shadowcount/DISTRIB;
} else {
cosfi = 0.0;
}
} else {
cosfi = 0.0;
}
Color->x = txt->color.x*(Ambient+cosfi);
Color->y = txt->color.y*(Ambient+cosfi);
Color->z = txt->color.z*(Ambient+cosfi);
if( txt->reflect > EPSILON ) {
ReflectVector( &NewDir, LinD, &Norm );
TmpCol.x = TmpCol.y = TmpCol.z = 0.0;
if( usedist && ( txt->roughness > EPSILON ) ) {
for( i = 0; i < DISTRIB; i++ ) {
DistribVector( &D, &NewDir, txt->roughness, txt->roughness );
NewDir2 = NewDir;
NewDir2.x += D.x; NewDir2.y += D.y; NewDir2.z += D.z;
TraceLine( &Pnt, &NewDir2, &TmpCol2, reccount-1 );
TmpCol.x += TmpCol2.x;
TmpCol.y += TmpCol2.y;
TmpCol.z += TmpCol2.z;
}
ScaleVector( &TmpCol, 1.0/DISTRIB );
} else {
TraceLine( &Pnt, &NewDir, &TmpCol, reccount-1 );
}
Color->x += TmpCol.x * txt->reflect;
Color->y += TmpCol.y * txt->reflect;
Color->z += TmpCol.z * txt->reflect;
}
} else {
/* Get sky-color (interpolate between horizon and zenit) */
A = sqrt( LinD->x*LinD->x + LinD->y*LinD->y );
if( A > 0.0 ) A = atan( fabs( LinD->z ) / A )*0.63661977;
else A = 1.0;
Color->x = Skycolor[1].x*A + Skycolor[0].x*(1.0-A);
Color->y = Skycolor[1].y*A + Skycolor[0].y*(1.0-A);
Color->z = Skycolor[1].z*A + Skycolor[0].z*(1.0-A);
}
/* Make sure that the color does not exceed the maximum level */
if(Color->x > 1.0) Color->x = 1.0;
if(Color->y > 1.0) Color->y = 1.0;
if(Color->z > 1.0) Color->z = 1.0;
}
}
