Ignore moving from the back to the front of a quad

git-svn-id: svn://cook.msm.cam.ac.uk:745/thrust3d/thrust3d@89 84d2e878-0bd5-11dd-ad15-13eda11d74c5

1 files changed, 8 insertions, 4 deletions

diff --git a/src/physics.c b/src/physics.c
index 6d3ed49..ce0b9bc 100644
--- a/src/physics.c
+++ b/src/physics.c
@@ -138,13 +138,10 @@ int physics_will_collide_face(double sx, double sy, double sz, double vx, double
 	
 }
 
+/* Check for collision with all faces in a primitive */
 static int physics_check_collide_all_faces(ModelInstance *obj, ModelInstance *other, Uint32 dt, int a,
 						double sx, double sy, double sz, double vx, double vy, double vz) {
 
-	const double nx = other->model->primitives[a]->normals[0];
-	const double ny = other->model->primitives[a]->normals[1];
-	const double nz = other->model->primitives[a]->normals[2];
-	
 	switch ( other->model->primitives[a]->type ) {
 	
 		case PRIMITIVE_QUADS : {
@@ -158,6 +155,13 @@ static int physics_check_collide_all_faces(ModelInstance *obj, ModelInstance *ot
 				int q;
 				double ttc;
 				
+				const double nx = other->model->primitives[a]->normals[3*(4*f)+0];
+				const double ny = other->model->primitives[a]->normals[3*(4*f)+1];
+				const double nz = other->model->primitives[a]->normals[3*(4*f)+2];
+				
+				/* Skip if moving from the back to the front of this quad */
+				if ( nx*vx + ny*vy + nz*vz > 0.0 ) continue;
+				
 				for ( q=0; q<4; q++ ) {
 					face[3*q + 0] = other->x + other->model->primitives[a]->vertices[3*((4*f)+q) + 0];
 					face[3*q + 1] = other->y + other->model->primitives[a]->vertices[3*((4*f)+q) + 1];