void sreFrustum::CalculateShadowCasterVolume(const Vector4D& lightpos, int nu_frustum_planes) {
nu_frustum_planes = maxf(nu_frustum_planes, SRE_NU_FRUSTUM_PLANES);
// Note: for beam lights, this might be inaccurate.
if (lightpos.w == 1.0f && Intersects(lightpos.GetPoint3D(), frustum_world)) {
// If the point light position is inside the view frustum, we only need to consider the
// set of visible objects.
shadow_caster_volume.nu_planes = nu_frustum_planes;
for (int i = 0; i < nu_frustum_planes; i++)
shadow_caster_volume.plane[i] = frustum_world.plane[i];
goto end;
}
// Calculate the convex hull enclosing the view frustum and the light source.
shadow_caster_volume.nu_planes = 0;
// Calculate the dot products between the frustum planes and the light source.
float dot[6] DST_ALIGNED(16);
// The SIMD-accelerated version check for 16-bytes aligned arrays, which is hard to
// guarantee in this case; otherwise, no SIMD will be used.
#if 1
dstCalculateDotProductsNx1(nu_frustum_planes, &frustum_world.plane[0],
lightpos, &dot[0]);
#else
for (int i = 0; i < nu_frustum_planes; i++)
dot[i] = Dot(frustum_world.plane[i], lightpos);
#endif
// For each frustum plane, add it if it is part of the convex hull.
for (int i = 0; i < nu_frustum_planes; i++)
if (dot[i] > 0) {
shadow_caster_volume.plane[shadow_caster_volume.nu_planes] = frustum_world.plane[i];
shadow_caster_volume.nu_planes++;
}
// printf("Shadow caster volume planes: from frustum: %d\n", shadow_caster_volume.nu_planes);
if (shadow_caster_volume.nu_planes == 0 && lightpos.w == 1.0f) {
// Special case: the point light source is behind the camera and there is no far plane.
// As a result, there is no plane from the frustum with a positive dot product. In
// this case, construct a volume consisting of the lightsource and four planes parallel
// to the frustum side planes but starting at the lightsource.
for (int i = 0; i < 4; i++) {
// Copy the normal.
shadow_caster_volume.plane[i] = frustum_world.plane[i];
// Calculate the distance such that the lightsource is in the plane.
shadow_caster_volume.plane[i].w = - Dot(frustum_world.plane[i].GetVector3D(),
lightpos.GetPoint3D());
}
shadow_caster_volume.nu_planes = 4;
goto end;
}
// For each pair of adjacent frustum planes, if one has a positive dot product and the other
// does not, calculate a new plane defined by the edge between those two frustum planes and
// the position of the light source, making sure the plane's normal direction faces inward.
// For directional lights, the plane runs parallel to the direction of the light.
nu_shadow_caster_edges = 0;
int n;
if (nu_frustum_planes == 5)
n = 8;
else
n = 12;
for (int i = 0; i < n; i++)
if ((dot[adjacent_plane[i].plane0] > 0 && dot[adjacent_plane[i].plane1] <= 0) ||
(dot[adjacent_plane[i].plane0] <= 0 && dot[adjacent_plane[i].plane1] > 0)) {
// printf("Setting plane from adjacent planes %d and %d using frustum vertices %d and %d\n",
// adjacent_plane[i].plane0, adjacent_plane[i].plane1, adjacent_plane[i].vertex0,
// adjacent_plane[i].vertex1);
if (lightpos.w == 1.0f)
shadow_caster_volume.plane[shadow_caster_volume.nu_planes] = dstPlaneFromPoints(
frustum_world.hull.vertex[adjacent_plane[i].vertex0],
frustum_world.hull.vertex[adjacent_plane[i].vertex1],
lightpos.GetPoint3D()
);
else {
shadow_caster_volume.plane[shadow_caster_volume.nu_planes] = dstPlaneFromPoints(
frustum_world.hull.vertex[adjacent_plane[i].vertex0],
frustum_world.hull.vertex[adjacent_plane[i].vertex1],
frustum_world.hull.vertex[adjacent_plane[i].vertex0] + lightpos.GetVector3D()
);
shadow_caster_edge[nu_shadow_caster_edges][0] = adjacent_plane[i].vertex0;
shadow_caster_edge[nu_shadow_caster_edges][1] = adjacent_plane[i].vertex1;
nu_shadow_caster_edges++;
}
// Make sure the normal is pointed inward, check by taking the dot product with the frustum
// "centroid".
shadow_caster_volume.plane[shadow_caster_volume.nu_planes].OrientPlaneTowardsPoint(
frustum_world.sphere.center);
shadow_caster_volume.nu_planes++;
}
end: ;
#if 0
printf("Light (%lf, %lf, %lf, %lf), %d planes in shadow caster volume.\n",
lightpos.x, lightpos.y, lightpos.z, lightpos.w, shadow_caster_volume.nu_planes);
for (int i = 0; i < shadow_caster_volume.nu_planes; i++)
printf("Plane %d: (%lf, %lf, %lf, %lf) ", i,
shadow_caster_volume.plane[i].x, shadow_caster_volume.plane[i].y,
shadow_caster_volume.plane[i].y, shadow_caster_volume.plane[i].w);
printf("\n");
#endif
}
