short RasterMapRaw::_GetFieldAtXY(unsigned int lx,
unsigned int ly) {
unsigned int ix = CombinedDivAndMod(lx);
unsigned int iy = CombinedDivAndMod(ly);
if ((ly>=(unsigned int)TerrainInfo.Rows)
||(lx>=(unsigned int)TerrainInfo.Columns)) {
return TERRAIN_INVALID;
}
short *tm = TerrainMem+ly*TerrainInfo.Columns+lx;
// perform piecewise linear interpolation
int h1 = *tm; // (x,y)
if (!ix && !iy) {
return h1;
}
if (lx+1 >= (unsigned int)TerrainInfo.Columns) {
return h1;
}
if (ly+1 >= (unsigned int)TerrainInfo.Rows) {
return h1;
}
int h3 = tm[TerrainInfo.Columns+1]; // (x+1, y+1)
if (ix>iy) {
// lower triangle
int h2 = tm[1]; // (x+1,y)
return (short)(h1+((ix*(h2-h1)-iy*(h2-h3))>>8));
} else {
short
RasterBuffer::GetInterpolated(unsigned lx, unsigned ly) const
{
// check x in range, and decompose fraction part
const unsigned int ix = CombinedDivAndMod(lx);
if (lx >= GetWidth())
return TERRAIN_INVALID;
// check y in range, and decompose fraction part
const unsigned int iy = CombinedDivAndMod(ly);
if (ly >= GetHeight())
return TERRAIN_INVALID;
return GetInterpolated(lx, ly, ix, iy);
}
