Rewriting BaseWindingForPlane() in polylib.c from the ground up. The behavior

[xonotic/netradiant.git] / tools / quake3 / common / polylib.c

diff --git a/tools/quake3/common/polylib.c b/tools/quake3/common/polylib.c
index 75caec6bcd4c93046bbc167994427131abf12d9c..839f7ea5d1ee3071fa7aa26539cb601ceadce9f7 100644 (file)
--- a/tools/quake3/common/polylib.c
+++ b/tools/quake3/common/polylib.c
@@ -207,6 +207,83 @@ BaseWindingForPlane
 =================
 */
 winding_t *BaseWindingForPlane (vec3_t normal, vec_t dist)
 =================
 */
 winding_t *BaseWindingForPlane (vec3_t normal, vec_t dist)

+{
+       // The goal in this function is to replicate the exact behavior that was in the original
+       // BaseWindingForPlane() function (see below).  The only thing we're going to change is the
+       // accuracy of the operation.  The original code gave a preference for the vup vector to start
+       // out as (0, 0, 1), unless the normal had a dominant Z value, in which case vup started out
+       // as (1, 0, 0).  After that, vup was "bent" [along the plane defined by normal and vup] to
+       // become perpendicular to normal.  After that the vright vector was computed as the cross
+       // product of vup and normal.
+
+       // Once these vectors are calculated, I'm constructing the winding points in exactly the same
+       // way as was done in the original function.  Orientation is the same.
+
+       // Note that the 4 points in the returned winding_t may actually not be necessary (3 might
+       // be enough).  However, I want to minimize the chance of ANY bugs popping up due to any
+       // change in behavior of this function.  Therefore, behavior stays exactly the same, except
+       // for precision of math.  Performance might be better in the new function as well.
+
+       int             x, i;
+       vec_t           max, v;
+       vec3_t          vright, vup, org;
+       winding_t       *w;
+
+       max = -BOGUS_RANGE;
+       x = -1;
+       for (i = 0; i < 3; i++) {
+               v = fabs(normal[i]);
+               if (v > max) {
+                       x = i;
+                       max = v;
+               }
+       }
+       if (x == -1) Error("BaseWindingForPlane: no axis found");
+
+       switch (x) {
+               case 0: // Fall through to next case.
+               case 1:
+                       vright[0] = -normal[1];
+                       vright[1] = normal[0];
+                       vright[2] = 0;
+                       break;
+               case 2:
+                       vright[0] = 0;
+                       vright[1] = -normal[2];
+                       vright[2] = normal[1];
+                       break;
+       }
+       CrossProduct(normal, vright, vup);
+
+       // IMPORTANT NOTE: vright and vup are NOT unit vectors at this point.
+       // However, normal, vup, and vright are pairwise perpendicular.
+
+       VectorSetLength(vup, MAX_WORLD_COORD * 2, vup);
+       VectorSetLength(vright, MAX_WORLD_COORD * 2, vright);
+       VectorScale(normal, dist, org);
+
+       w = AllocWinding(4);
+
+       VectorSubtract(org, vright, w->p[0]);
+       VectorAdd(w->p[0], vup, w->p[0]);
+
+       VectorAdd(org, vright, w->p[1]);
+       VectorAdd(w->p[1], vup, w->p[1]);
+
+       VectorAdd(org, vright, w->p[2]);
+       VectorSubtract(w->p[2], vup, w->p[2]);
+
+       VectorSubtract(org, vright, w->p[3]);
+       VectorSubtract(w->p[3], vup, w->p[3]);
+
+       w->numpoints = 4;
+
+       return w;
+}
+
+// Old function, not used but here for reference.  Please do not modify it.
+// (You may remove it at some point.)
+winding_t *_BaseWindingForPlane_orig_(vec3_t normal, vec_t dist)

 {
        int             i, x;
        vec_t   max, v;
 {
        int             i, x;
        vec_t   max, v;