color trace(ray * primary) {
if (primary->depth > 0) {
VNorm(&primary->d);
reset_intersection(primary->intstruct);
intersect_objects(primary);
return shader(primary);
}
/* if ray is truncated, return the background as its color */
return primary->scene->background;
}
color shader(ray * incident) {
color col, diffuse, phongcol;
vector N, L, hit;
ray shadowray;
flt inten, t, Llen;
object * obj;
int numints, i;
point_light * li;
numints=closest_intersection(&t, &obj, incident->intstruct);
/* find the number of intersections */
/* and return the closest one. */
if (numints < 1) {
/* if there weren't any object intersections then return the */
/* background color for the pixel color. */
return incident->scene->background;
}
if (obj->tex->islight) { /* if the current object is a light, then we */
return obj->tex->col; /* will only use the objects ambient color */
}
RAYPNT(hit, (*incident), t) /* find the point of intersection from t */
obj->methods->normal(obj, &hit, incident, &N); /* find the surface normal */
/* execute the object's texture function */
col = obj->tex->texfunc(&hit, obj->tex, incident);
diffuse.r = 0.0;
diffuse.g = 0.0;
diffuse.b = 0.0;
phongcol = diffuse;
if ((obj->tex->diffuse > 0.0) || (obj->tex->phong > 0.0)) {
for (i=0; i<numlights; i++) { /* loop for light contributions */
li=lightlist[i]; /* set li=to the current light */
VSUB(li->ctr, hit, L) /* find the light vector */
/* calculate the distance to the light from the hit point */
Llen = sqrt(L.x*L.x + L.y*L.y + L.z*L.z) + EPSILON;
L.x /= Llen; /* normalize the light direction vector */
L.y /= Llen;
L.z /= Llen;
VDOT(inten, N, L) /* light intensity */
/* add in diffuse lighting for this light if we're facing it */
if (inten > 0.0) {
/* test for a shadow */
shadowray.intstruct = incident->intstruct;
shadowray.flags = RT_RAY_SHADOW | RT_RAY_BOUNDED;
incident->serial++;
shadowray.serial = incident->serial;
shadowray.mbox = incident->mbox;
shadowray.o = hit;
shadowray.d = L;
shadowray.maxdist = Llen;
shadowray.s = hit;
shadowray.e = li->ctr;
shadowray.scene = incident->scene;
reset_intersection(incident->intstruct);
intersect_objects(&shadowray);
if (!shadow_intersection(incident->intstruct, Llen)) {
/* XXX now that opacity is in the code, have to be more careful */
ColorAddS(&diffuse, &li->tex->col, inten);
/* phong type specular highlights */
if (obj->tex->phong > 0.0) {
flt phongval;
phongval = shade_phong(incident, &hit, &N, &L, obj->tex->phongexp);
if (obj->tex->phongtype)
ColorAddS(&phongcol, &col, phongval);
else
ColorAddS(&phongcol, &(li->tex->col), phongval);
}
}
}
}
}
ColorScale(&diffuse, obj->tex->diffuse);
col.r *= (diffuse.r + obj->tex->ambient); /* do a product of the */
col.g *= (diffuse.g + obj->tex->ambient); /* diffuse intensity with */
col.b *= (diffuse.b + obj->tex->ambient); /* object color + ambient */
if (obj->tex->phong > 0.0) {
ColorAccum(&col, &phongcol);
}
/* spawn reflection rays if necessary */
/* note: this will overwrite the old intersection list */
if (obj->tex->specular > 0.0) {
color specol;
specol = shade_reflection(incident, &hit, &N, obj->tex->specular);
ColorAccum(&col, &specol);
}
/* spawn transmission rays / refraction */
/* note: this will overwrite the old intersection list */
if (obj->tex->opacity < 1.0) {
color transcol;
transcol = shade_transmission(incident, &hit, 1.0 - obj->tex->opacity);
ColorAccum(&col, &transcol);
}
return col; /* return the color of the shaded pixel... */
}