Convert from point to bounding box visibility test

[grits] / src / roam.c

diff --git a/src/roam.c b/src/roam.c
index 94416b96abbae7bd135ec73c240f791783a90072..3de5b5b7258ea938116827bf815ac2a1b5fee66e 100644 (file)
--- a/src/roam.c
+++ b/src/roam.c
@@ -326,19 +326,20 @@ static void roam_triangle_sync_neighbors(RoamTriangle *new, RoamTriangle *old, R
        else g_assert_not_reached();
 }
 
-static gboolean roam_point_visible(RoamPoint *triangle, RoamSphere *sphere)
-{
-       gint *view = sphere->view->view;
-       return triangle->px > view[0] && triangle->px < view[2] &&
-              triangle->py > view[1] && triangle->py < view[3] &&
-              triangle->pz > 0       && triangle->pz < 1;
-}
 static gboolean roam_triangle_visible(RoamTriangle *triangle, RoamSphere *sphere)
 {
-       /* Do this with a bounding box */
-       return roam_point_visible(triangle->p.l, sphere) ||
-              roam_point_visible(triangle->p.m, sphere) ||
-              roam_point_visible(triangle->p.r, sphere);
+       RoamPoint *l = triangle->p.l;
+       RoamPoint *m = triangle->p.m;
+       RoamPoint *r = triangle->p.r;
+       gdouble min_x = MIN(MIN(l->px, m->px), r->px);
+       gdouble max_x = MAX(MAX(l->px, m->px), r->px);
+       gdouble min_y = MIN(MIN(l->py, m->py), r->py);
+       gdouble max_y = MAX(MAX(l->py, m->py), r->py);
+       gint *view = sphere->view->view;
+       return !(max_x < view[0] || min_x > view[2] ||
+                max_y < view[1] || min_y > view[3]) &&
+                l->pz > 0 && m->pz > 0 && r->pz > 0 &&
+                l->pz < 1 && m->pz < 1 && r->pz < 1;
 }
 
 /**
@@ -356,7 +357,6 @@ void roam_triangle_update_errors(RoamTriangle *triangle, RoamSphere *sphere)
        roam_point_update_projection(triangle->p.m, sphere->view);
        roam_point_update_projection(triangle->p.r, sphere->view);
 
-       /* Not exactly correct, could be out on both sides (middle in) */
        if (!roam_triangle_visible(triangle, sphere)) {
                triangle->error = -1;
        } else {