float CGround::LineGroundCol(float3 from, float3 to)
{
float savedLength = 0.0f;
if (from.z > float3::maxzpos && to.z < float3::maxzpos) {
// a special case since the camera in overhead mode can often do this
float3 dir = to - from;
float maxLength = dir.Length();
dir /= maxLength;
savedLength = -(from.z - float3::maxzpos) / dir.z;
from += dir * savedLength;
}
from.CheckInBounds();
float3 dir = to - from;
float maxLength = dir.Length();
dir /= maxLength;
if (from.x + dir.x * maxLength < 1.0f)
maxLength = (1.0f - from.x) / dir.x;
else if (from.x + dir.x * maxLength > float3::maxxpos)
maxLength = (float3::maxxpos - from.x) / dir.x;
if (from.z + dir.z * maxLength < 1.0f)
maxLength = (1.0f - from.z) / dir.z;
else if (from.z + dir.z * maxLength > float3::maxzpos)
maxLength = (float3::maxzpos - from.z) / dir.z;
to = from + dir * maxLength;
const float dx=to.x-from.x;
const float dz=to.z-from.z;
float xp=from.x;
float zp=from.z;
float ret;
float xn,zn;
bool keepgoing=true;
if((floor(from.x/SQUARE_SIZE)==floor(to.x/SQUARE_SIZE)) && (floor(from.z/SQUARE_SIZE)==floor(to.z/SQUARE_SIZE))) {
ret = LineGroundSquareCol(from,to,(int)floor(from.x/SQUARE_SIZE),(int)floor(from.z/SQUARE_SIZE));
if(ret>=0) {
return ret;
}
} else if(floor(from.x/SQUARE_SIZE)==floor(to.x/SQUARE_SIZE)) {
while(keepgoing) {
ret = LineGroundSquareCol(from,to,(int)floor(xp/SQUARE_SIZE),(int)floor(zp/SQUARE_SIZE));
if(ret>=0) {
return ret+savedLength;
}
keepgoing=fabs(zp-from.z)<fabs(dz);
if(dz>0)
zp+=SQUARE_SIZE;
else
zp-=SQUARE_SIZE;
}
// if you hit this the collision detection hit an infinite loop
assert(!keepgoing);
} else if(floor(from.z/SQUARE_SIZE)==floor(to.z/SQUARE_SIZE)) {
while(keepgoing) {
ret = LineGroundSquareCol(from,to,(int)floor(xp/SQUARE_SIZE),(int)floor(zp/SQUARE_SIZE));
if(ret>=0) {
return ret+savedLength;
}
keepgoing=fabs(xp-from.x)<fabs(dx);
if(dx>0)
xp+=SQUARE_SIZE;
else
xp-=SQUARE_SIZE;
}
// if you hit this the collision detection hit an infinite loop
assert(!keepgoing);
} else {
while(keepgoing) {
float xs, zs;
// Push value just over the edge of the square
// This is the best accuracy we can get with floats:
// add one digit and (xp*constant) reduces to xp itself
// This accuracy means that at (16384,16384) (lower right of 32x32 map)
// 1 in every 1/(16384*1e-7f/8)=4883 clicks on the map will be ignored.
if (dx>0) xs = floor(xp*1.0000001f/SQUARE_SIZE);
else xs = floor(xp*0.9999999f/SQUARE_SIZE);
if (dz>0) zs = floor(zp*1.0000001f/SQUARE_SIZE);
else zs = floor(zp*0.9999999f/SQUARE_SIZE);
ret = LineGroundSquareCol(from, to, (int)xs, (int)zs);
if(ret>=0) {
return ret+savedLength;
}
keepgoing=fabs(xp-from.x)<fabs(dx) && fabs(zp-from.z)<fabs(dz);
if(dx>0) {
// distance xp to right edge of square (xs,zs) divided by dx, xp += xn*dx puts xp on the right edge
xn=(xs*SQUARE_SIZE+SQUARE_SIZE-xp)/dx;
} else {
// distance xp to left edge of square (xs,zs) divided by dx, xp += xn*dx puts xp on the left edge
xn=(xs*SQUARE_SIZE-xp)/dx;
}
if(dz>0) {
// distance zp to bottom edge of square (xs,zs) divided by dz, zp += zn*dz puts zp on the bottom edge
zn=(zs*SQUARE_SIZE+SQUARE_SIZE-zp)/dz;
} else {
// distance zp to top edge of square (xs,zs) divided by dz, zp += zn*dz puts zp on the top edge
zn=(zs*SQUARE_SIZE-zp)/dz;
}
// xn and zn are always positive, minus signs are divided out above
// this puts (xp,zp) exactly on the first edge you see if you look from (xp,zp) in the (dx,dz) direction
if(xn<zn) {
xp+=xn*dx;
zp+=xn*dz;
} else {
xp+=zn*dx;
zp+=zn*dz;
}
}
}
return -1;
}
float CGround::LineGroundCol(float3 from, float3 to, bool synced)
{
const float* hm = readMap->GetSharedCornerHeightMap(synced);
const float3* nm = readMap->GetSharedFaceNormals(synced);
const float3 pfrom = from;
// only for performance -> skip part that can impossibly collide
// with the terrain, cause it is above map's current max height
ClampInMapHeight(from, to);
// handle special cases where the ray origin is out of bounds:
// need to move <from> to the closest map-edge along the ray
// (if both <from> and <to> are out of bounds, the ray might
// still hit)
// clamping <from> naively would change the direction of the
// ray, hence we save the distance along it that got skipped
ClampLineInMap(from, to);
if (from == to) {
// ClampLineInMap & ClampInMapHeight set `from == to == vec(-1,-1,-1)`
// in case the line is outside of the map
return -1.0f;
}
const float skippedDist = pfrom.distance(from);
if (synced) { //TODO do this in unsynced too once the map border rendering is finished?
// check if our start position is underground (assume ground is unpassable for cannons etc.)
const int sx = from.x / SQUARE_SIZE;
const int sz = from.z / SQUARE_SIZE;
if (from.y <= hm[sz * mapDims.mapxp1 + sx]) {
return 0.0f + skippedDist;
}
}
const float dx = to.x - from.x;
const float dz = to.z - from.z;
const int dirx = (dx > 0.0f) ? 1 : -1;
const int dirz = (dz > 0.0f) ? 1 : -1;
// Clamping is done cause LineGroundSquareCol() operates on the 2 triangles faces each heightmap
// square is formed of.
const float ffsx = Clamp(from.x / SQUARE_SIZE, 0.0f, (float)mapDims.mapx);
const float ffsz = Clamp(from.z / SQUARE_SIZE, 0.0f, (float)mapDims.mapy);
const float ttsx = Clamp(to.x / SQUARE_SIZE, 0.0f, (float)mapDims.mapx);
const float ttsz = Clamp(to.z / SQUARE_SIZE, 0.0f, (float)mapDims.mapy);
const int fsx = ffsx;
const int fsz = ffsz;
const int tsx = ttsx;
const int tsz = ttsz;
bool keepgoing = true;
if ((fsx == tsx) && (fsz == tsz)) {
// <from> and <to> are the same
const float ret = LineGroundSquareCol(hm, nm, from, to, fsx, fsz);
if (ret >= 0.0f) {
return (ret + skippedDist);
}
} else if (fsx == tsx) {
// ray is parallel to z-axis
int zp = fsz;
while (keepgoing) {
const float ret = LineGroundSquareCol(hm, nm, from, to, fsx, zp);
if (ret >= 0.0f) {
return (ret + skippedDist);
}
keepgoing = (zp != tsz);
zp += dirz;
}
} else if (fsz == tsz) {
// ray is parallel to x-axis
int xp = fsx;
while (keepgoing) {
const float ret = LineGroundSquareCol(hm, nm, from, to, xp, fsz);
if (ret >= 0.0f) {
return (ret + skippedDist);
}
keepgoing = (xp != tsx);
xp += dirx;
}
} else {
// general case
const float rdsx = SQUARE_SIZE / dx; // := 1 / (dx / SQUARE_SIZE)
const float rdsz = SQUARE_SIZE / dz;
// we need to shift the `test`-point in case of negative directions
// case: dir<0
// ___________
// | | | |
// |___|___|___|
// ^cur
// ^cur + dir
// > < range of int(cur + dir)
// ^wanted test point := cur - epsilon
// you can set epsilon=0 and then handle the `beyond end`-case (xn >= 1.0f && zn >= 1.0f) separate
// (we already need to do so cause of floating point precision limits, so skipping epsilon doesn't add
// any additional performance cost nor precision issue)
//
// case : dir>0
// in case of `dir>0` the wanted test point is idential with `cur + dir`
const float testposx = (dx > 0.0f) ? 0.0f : 1.0f;
const float testposz = (dz > 0.0f) ? 0.0f : 1.0f;
int curx = fsx;
int curz = fsz;
while (keepgoing) {
// do the collision test with the squares triangles
const float ret = LineGroundSquareCol(hm, nm, from, to, curx, curz);
if (ret >= 0.0f) {
return (ret + skippedDist);
}
// check if we reached the end already and need to stop the loop
const bool endReached = (curx == tsx && curz == tsz);
const bool beyondEnd = ((curx - tsx) * dirx > 0) || ((curz - tsz) * dirz > 0);
assert(!beyondEnd);
keepgoing = !endReached && !beyondEnd;
if (!keepgoing)
break;
// calculate the `normalized position` of the next edge in x & z direction
// `normalized position`:=n : x = from.x + n * (to.x - from.x) (with 0<= n <=1)
int nextx = curx + dirx;
int nextz = curz + dirz;
float xn = (nextx + testposx - ffsx) * rdsx;
float zn = (nextz + testposz - ffsz) * rdsz;
// handles the following 2 case:
// case1: (floor(to.x) == to.x) && (to.x < from.x)
// In this case we calculate xn at to.x but set curx = to.x - 1,
// and so we would be beyond the end of the ray.
// case2: floating point precision issues
if ((nextx - tsx) * dirx > 0) { xn=1337.0f; nextx=tsx; }
if ((nextz - tsz) * dirz > 0) { zn=1337.0f; nextz=tsz; }
// advance to the next nearest edge in either x or z dir, or in the case we reached the end make sure
// we set it to the exact square positions (floating point precision sometimes hinders us to hit it)
if (xn >= 1.0f && zn >= 1.0f) {
assert(curx != nextx || curz != nextz);
curx = nextx;
curz = nextz;
} else if (xn < zn) {
assert(curx != nextx);
curx = nextx;
} else {
assert(curz != nextz);
curz = nextz;
}
}
}
return -1.0f;
}
