// intersect a ray with the mesh
bool TXGrid3D::IntersectRay(const CVector3f& start, const CVector3f& end)
{
// pick rays
m_rays.push_back(TXRay(start, end));
CVector3f dir;
dir.Sub(start,end);
int idir[3] = {
fabs(dir.GetX()) < DBL_EPSILON ? 0 : (dir.GetX() > 0 ? 1 : -1),
fabs(dir.GetY()) < DBL_EPSILON ? 0 : (dir.GetY() > 0 ? 1 : -1),
fabs(dir.GetZ()) < DBL_EPSILON ? 0 : (dir.GetZ() > 0 ? 1 : -1) };
double dist = 0;
CVector3f pos;
pos.Sub(end, m_min);
int ix = (int)floor((end.GetX() - m_min.GetX())/m_xstep),
iy = (int)floor((end.GetY() - m_min.GetY())/m_ystep),
iz = (int)floor((end.GetZ() - m_min.GetZ())/m_zstep);
double tx = 1.0, ty = 1.0, tz = 1.0;
// first cell
ix = MIN(MAX(ix, 0), m_size-1);
iy = MIN(MAX(iy, 0), m_size-1);
iz = MIN(MAX(iz, 0), m_size-1);
// intersection test, from end to start
while ((dist < 1) && (ix >= 0) && (ix < m_size) &&(iy >= 0) && (iy < m_size) && (iz >= 0) && (iz < m_size))
{
int csz = m_grid[ix][iy][iz].size();
for (int i=0; i<csz; i++)
{
TXGridTriangle* gt = m_grid[ix][iy][iz][i];
double rpdot = dir.Dot(gt->m_n);
if (rpdot != 0)
{
CVector3f tmp;
tmp.Sub(gt->m_t->m_v[0]->m_pos,end);
double t = tmp.Dot(gt->m_n) / rpdot;
if (t > DBL_EPSILON && t < 1)
{
CVector3f pt;
pt.ScaleAdd(t,dir,end);
CVector3f pt0,pt1,pt2;
pt0.Sub(pt,gt->m_t->m_v[0]->m_pos);
pt1.Sub(pt,gt->m_t->m_v[1]->m_pos);
pt2.Sub(pt,gt->m_t->m_v[2]->m_pos);
if (pt0.Dot(gt->m_en1)> -DBL_EPSILON &&
pt1.Dot(gt->m_en2)>-DBL_EPSILON &&
pt2.Dot(gt->m_en3)>-DBL_EPSILON)
{
m_rays[m_rays.size()-1].m_p = t;
return true;
}
}
}
}
// next cell
if (idir[0] != 0)
tx = (m_min.GetX() + (ix+(idir[0]+1)/2)*m_xstep - end.GetX()) / dir.GetX();
if (idir[1] != 0)
ty = (m_min.GetY() + (iy+(idir[1]+1)/2)*m_ystep - end.GetY()) / dir.GetY();
if (idir[2] != 0)
tz = (m_min.GetZ() + (iz+(idir[2]+1)/2)*m_zstep - end.GetZ()) / dir.GetZ();
if ((tx <= ty) && (tx <= tz))
{
dist = tx, ix += idir[0];
if (ty == tx) iy += idir[1];
if (tz == tx) iz += idir[2];
}
else if (ty <= tz)
{
dist = ty, iy += idir[1];
if (tz == ty) iz += idir[2];
}
else dist = tz, iz += idir[2];
}
return false;
}
