engine: common: fixed lightmap shifting caused by insufficent precision in Mod_CalcSurfaceExtents

engine/common/mod_bmodel.c

@@ -1020,8 +1020,8 @@ Fills in surf->texturemins[] and surf->extents[]
 */
 static void Mod_CalcSurfaceExtents( msurface_t *surf )
 {
-	float		mins[2], maxs[2], val;
+	double		mins[2], maxs[2], val;
-	float		lmmins[2], lmmaxs[2];
+	double		lmmins[2], lmmaxs[2];
 	int		bmins[2], bmaxs[2];
 	int		i, j, e, sample_size;
 	mextrasurf_t	*info = surf->info;
@@ -1049,14 +1049,14 @@ static void Mod_CalcSurfaceExtents( msurface_t *surf )
 
 		for( j = 0; j < 2; j++ )
 		{
-			val = DotProduct( v->position, surf->texinfo->vecs[j] ) + surf->texinfo->vecs[j][3];
+			val = DotProductPrecise( v->position, surf->texinfo->vecs[j] ) + surf->texinfo->vecs[j][3];
 			mins[j] = Q_min( val, mins[j] );
 			maxs[j] = Q_max( val, maxs[j] );
 		}
 
 		for( j = 0; j < 2; j++ )
 		{
-			val = DotProduct( v->position, info->lmvecs[j] ) + info->lmvecs[j][3];
+			val = DotProductPrecise( v->position, info->lmvecs[j] ) + info->lmvecs[j][3];
 			lmmins[j] = Q_min( val, lmmins[j] );
 			lmmaxs[j] = Q_max( val, lmmaxs[j] );
 		}

public/xash3d_mathlib.h

@@ -93,6 +93,7 @@ GNU General Public License for more details.
 #define DotProduct(x,y) ((x)[0]*(y)[0]+(x)[1]*(y)[1]+(x)[2]*(y)[2])
 #define DotProductAbs(x,y) (abs((x)[0]*(y)[0])+abs((x)[1]*(y)[1])+abs((x)[2]*(y)[2]))
 #define DotProductFabs(x,y) (fabs((x)[0]*(y)[0])+fabs((x)[1]*(y)[1])+fabs((x)[2]*(y)[2]))
+#define DotProductPrecise(x,y) ((double)(x)[0]*(double)(y)[0]+(double)(x)[1]*(double)(y)[1]+(double)(x)[2]*(double)(y)[2])
 #define CrossProduct(a,b,c) ((c)[0]=(a)[1]*(b)[2]-(a)[2]*(b)[1],(c)[1]=(a)[2]*(b)[0]-(a)[0]*(b)[2],(c)[2]=(a)[0]*(b)[1]-(a)[1]*(b)[0])
 #define Vector2Subtract(a,b,c) ((c)[0]=(a)[0]-(b)[0],(c)[1]=(a)[1]-(b)[1])
 #define VectorSubtract(a,b,c) ((c)[0]=(a)[0]-(b)[0],(c)[1]=(a)[1]-(b)[1],(c)[2]=(a)[2]-(b)[2])