bool Intersect(const Terrain &t, const WFMath::Point<3> &sPt, const WFMath::Vector<3>& dir,
WFMath::Point<3> &intersection, WFMath::Vector<3> &normal, float &par)
{
//FIXME early reject using segment max
//FIXME handle height point getting in a more optimal way
//FIXME early reject for vertical ray
// check if startpoint is below ground
if (HOT(t, sPt) < 0.0) return true;
float paraX=0.0, paraY=0.0; //used to store the parametric gap between grid crossings
float pX, pY; //the accumulators for the parametrics as we traverse the ray
float h1,h2,h3,h4,height;
WFMath::Point<3> last(sPt), next(sPt);
WFMath::Vector<3> nDir(dir);
nDir.normalize();
float dirLen = dir.mag();
//work out where the ray first crosses an X grid line
if (dir[0] != 0.0f) {
paraX = 1.0f/dir[0];
float crossX = (dir[0] > 0.0f) ? gridceil(last[0]) : gridfloor(last[0]);
pX = (crossX - last[0]) * paraX;
pX = std::min(pX, 1.0f);
}
else { //parallel: never crosses
pX = 1.0f;
}
//work out where the ray first crosses a Y grid line
if (dir[1] != 0.0f) {
paraY = 1.0f/dir[1];
float crossY = (dir[1] > 0.0f) ? gridceil(last[1]) : gridfloor(last[1]);
pY = (crossY - sPt[1]) * paraY;
pY = std::min(pY, 1.0f);
}
else { //parallel: never crosses
pY = 1.0f;
}
//ensure we traverse the ray forwards
paraX = std::abs(paraX);
paraY = std::abs(paraY);
bool endpoint = false;
//check each candidate tile for an intersection
while (1) {
last = next;
if (pX < pY) { // cross x grid line first
next = sPt + (pX * dir);
pX += paraX; // set x accumulator to current p
}
else { //cross y grid line first
next = sPt + (pY * dir);
if (pX == pY) {
pX += paraX; //unusual case where ray crosses corner
}
pY += paraY; // set y accumulator to current p
}
//FIXME these gets could be optimized a bit
float x= (dir[0] > 0) ? std::floor(last[0]) : std::floor(next[0]);
float y= (dir[1] > 0) ? std::floor(last[1]) : std::floor(next[1]);
h1 = t.get(x, y);
h2 = t.get(x, y+1);
h3 = t.get(x+1, y+1);
h4 = t.get(x+1, y);
height = std::max( std::max(h1, h2),
std::max(h3, h4));
if ( (last[2] < height) || (next[2] < height) ) {
// possible intersect with this tile
if (cellIntersect(h1, h2, h3, h4, x, y, nDir, dirLen, sPt,
intersection, normal, par)) {
return true;
}
}
if ((pX >= 1.0f) && (pY >= 1.0f)) {
if (endpoint) {
break;
}
else endpoint = true;
}
}
return false;
}
bool Intersect(const Terrain &t, const WFMath::Point<3> &pt)
{
return HOT(t, pt) <= 0.0;
}
bool Intersect(Terrain const &t, const WFMath::Point<3> &pt)
{
float h;
return HOT(t, pt, h) && h <= 0.0;
}
