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- GetClosestSpriteSectors: replace distance calculation with proper math.

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No need to sample multiple points along the wall if we can just properly calculate the actual distance. :)
This commit is contained in:
Christoph Oelckers 2021-11-16 21:36:46 +01:00
parent d2f0934726
commit 12c26976f0
2 changed files with 27 additions and 28 deletions
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23
source/core/gamefuncs.h
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@ -251,3 +251,26 @@ inline int sectnum(sectortype* sect)
return int(sect - sector);
}
inline double SquareDist(double lx1, double ly1, double lx2, double ly2)
{
double dx = lx2 - lx1;
double dy = ly2 - ly1;
return dx * dx + dy * dy;
}
inline double SquareDistToWall(double px, double py, const walltype* wal)
{
double lx1 = wal->x;
double ly1 = wal->y;
double lx2 = wal->point2Wall()->x;
double ly2 = wal->point2Wall()->y;
double wall_length = SquareDist(lx1, ly1, lx2, ly2);
if (wall_length == 0) return SquareDist(px, py, lx1, ly1);
double t = ((px - lx1) * (lx2 - lx1) + (py - ly1) * (ly2 - ly1)) / wall_length;
t = clamp(t, 0., 1.);
return SquareDist(px, py, lx1 + t * (lx2 - lx1), ly1 + t * (ly2 - ly1));
}

32
source/games/blood/src/gameutil.cpp
View file

@ -761,6 +761,7 @@ BitArray GetClosestSpriteSectors(int nSector, int x, int y, int nDist, TArray<in
BitArray sectorMap(numsectors); // this gets returned to the caller.
sectorMap.Zero();
sectorMap.Set(nSector);
double nDist4sq = 256. * nDist * nDist; // (nDist * 16)^2 - * 16 to account for Build's 28.4 fixed point format.
BFSSearch search(numsectors, nSector);
@ -778,35 +779,10 @@ BitArray GetClosestSpriteSectors(int nSector, int x, int y, int nDist, TArray<in
continue;
withinRange = CheckProximityWall(wal.point2, x, y, nDist);
}
else // new method
else // new method using proper math and no bad shortcut.
{
// Q: do this with proper math?
int x1 = wal.x, y1 = wal.y;
int x2 = wal.point2Wall()->x, y2 = wal.point2Wall()->y;
int point1Dist = approxDist(x - x1, y - y1); // setup edge distance needed for below loop (determines which point to shift closer to center)
int point2Dist = approxDist(x - x2, y - y2);
int nLength = approxDist(x1 - x2, y1 - y2);
const int nDist4 = nDist << 4;
nLength = ClipRange(nLength / (nDist4 + (nDist4 >> 1)), 1, 4); // always test midpoint at least once, and never split more than 4 times
for (int k = 0; true; k++) // check both points of wall and subdivide span into smaller chunks towards target
{
withinRange = (point1Dist < nDist4) || (point2Dist < nDist4); // check if both points of span is within radius
if (withinRange)
break;
if (k == nLength) // reached end
break;
const int xcenter = (x1 + x2) >> 1, ycenter = (y1 + y2) >> 1;
if (point1Dist < point2Dist) // shift closest side of wall towards target point, and refresh point distance values
{
x2 = xcenter, y2 = ycenter;
point2Dist = approxDist(x - x2, y - y2);
}
else
{
x1 = xcenter, y1 = ycenter;
point1Dist = approxDist(x - x1, y - y1);
}
}
double dist1 = SquareDistToWall(x, y, &wal);
withinRange = dist1 <= nDist4sq;
}
if (withinRange) // if new sector is within range, add it to the processing queue
{