poly edge crossing FOUR (ouch, that was unexpected) cube faces partially taken

care of. I have to fill in the incomplete faces (hmm, that will be interesting)
and figure out why one corner in one of my test cases is sometimes set and
sometimes not. Hmm, might be confused buy the enter/leave info from that edge.

source/gl_sky_clip.c

@@ -135,7 +135,7 @@ determine_face (vec3_t v)
 		y = x - ___ v
 		        v.n
 */
-static void
+static int
 find_intersect (int face1, vec3_t x1, int face2, vec3_t x2, vec3_t y)
 {
 	vec3_t n;					// normal to the plane formed by the eye and
@@ -144,12 +144,14 @@ find_intersect (int face1, vec3_t x1, int face2, vec3_t x2, vec3_t y)
 								// always on an axis plane.
 	vec3_t v = {0, 0, 0};		// direction vector of cube edge. always +ve
 	vec_t x_n, v_n;				// x.n and v.n
+	int axis;
 	vec3_t t;
 
 	x[face1 % 3] = 1024 * (1 - 2 * (face1 / 3));
 	x[face2 % 3] = 1024 * (1 - 2 * (face2 / 3));
 
-	v[3 - ((face1 % 3) + (face2 % 3))] = 1;
+	axis = 3 - ((face1 % 3) + (face2 % 3));
+	v[axis] = 1;
 
 	CrossProduct (x1, x2, n);
 
@@ -157,6 +159,8 @@ find_intersect (int face1, vec3_t x1, int face2, vec3_t x2, vec3_t y)
 	v_n = DotProduct (v, n);
 	VectorScale (v, x_n / v_n, t);
 	VectorSubtract (x, t, y);
+
+	return axis;
 }
 
 /*
@@ -350,13 +354,18 @@ fixup_center_face (struct box_def *box, int c_face)
 	the edge :). The poly edge is going from face 1 to face 2 (for
 	enter/leave purposes).
 */
-static void
+static int
 cross_cube_edge (struct box_def *box, int face1, vec3_t v1, int face2,
 				 vec3_t v2)
 {
 	vec3_t l;
+	int axis;
 
-	find_intersect (face1, v1, face2, v2, l);
+	axis = find_intersect (face1, v1, face2, v2, l);
+	if (l[axis] > 1024)
+		return axis;
+	else if (l[axis] < -1024)
+		return axis + 3;
 
 	box[face1].leave_vertex = box[face1].poly.numverts;
 	add_vertex(box, face1, l);
@@ -364,6 +373,8 @@ cross_cube_edge (struct box_def *box, int face1, vec3_t v1, int face2,
 	enter_face (box, face1, face2);
 	box[face2].enter_vertex = box[face2].poly.numverts;
 	add_vertex(box, face2, l);
+
+	return -1;
 }
 
 static void
@@ -409,6 +420,15 @@ fix_missed_vertexen (struct box_def *box, int *faces, int face_count)
 	}
 }
 
+static void
+visit_cube_face(int *visited_faces, int *faces_flags, int *face_count, int face)
+{
+	if (!faces_flags[face]) {
+		faces_flags[face] = 1;
+		visited_faces[(*face_count)++] = face;
+	}
+}
+
 void
 R_DrawSkyBoxPoly (glpoly_t *poly)
 {
@@ -443,29 +463,42 @@ R_DrawSkyBoxPoly (glpoly_t *poly)
 		VectorSubtract (poly->verts[i], r_refdef.vieworg, v);
 		face = determine_face (v);
 		if (face != prev_face) {
-			if ((face % 3) == (prev_face % 3)) {
+			int x_face = -1;
-				vec3_t x;
+			if ((face % 3) == (prev_face % 3)
-				int x_face;
+				|| (x_face = cross_cube_edge (box, prev_face, last_v,
+											  face, v)) >= 0) {
+				vec3_t x, y;
+				int y_face;
 
 				VectorAdd (v, last_v, x);
 				VectorScale (x, 0.5, x);
-				x_face = determine_face (x);
+				if (x_face == -1) {
-
+					x_face = determine_face (x);
-				if (!faces_flags[x_face]) {
-					faces_flags[x_face] = 1;
-					visited_faces[face_count++] = x_face;
 				}
 
-				cross_cube_edge (box, prev_face, last_v, x_face, x);
+				if ((y_face = cross_cube_edge (box, prev_face, last_v,
-				cross_cube_edge (box, x_face, x, face, v);
+											   x_face, x)) >= 0) {
-			} else {
+					VectorAdd (last_v, x, y);
-				cross_cube_edge (box, prev_face, last_v, face, v);
+					VectorScale (y, 0.5, y);
+					cross_cube_edge (box, prev_face, last_v, y_face, y);
+					cross_cube_edge (box, y_face, y, x_face, x);
+
+					visit_cube_face (visited_faces, faces_flags, &face_count, y_face);
+				}
+
+				visit_cube_face (visited_faces, faces_flags, &face_count, x_face);
+
+				if ((y_face = cross_cube_edge (box, x_face, x, face, v)) >= 0) {
+					VectorAdd (x, v, y);
+					VectorScale (y, 0.5, y);
+					cross_cube_edge (box, x_face, x, y_face, y);
+					cross_cube_edge (box, y_face, y, face, v);
+
+					visit_cube_face (visited_faces, faces_flags, &face_count, y_face);
+				}
 			}
 		}
-		if (!faces_flags[face]) {
+		visit_cube_face (visited_faces, faces_flags, &face_count, face);
-			faces_flags[face] = 1;
-			visited_faces[face_count++] = face;
-		}
 		add_vertex(box, face, v);
 
 		VectorCopy (v, last_v);