Fix the light position to be outside of the bounds of the shadow casters.

2 files changed, 13 insertions, 1 deletions

diff --git a/glass.c b/glass.c
index 36bb3fe..d79ad73 100644
--- a/glass.c
+++ b/glass.c
@@ -95,7 +95,7 @@ struct revolved_object ring;
 GLuint normalmap_tex, heightmap_tex;
 static GLboolean display_shadow_map = GL_FALSE;
 
-static const GLUvec4 light_start_world = {{0.0, 5.0, 15.0, 1.0}};
+static const GLUvec4 light_start_world = {{0.0, 10.0, 25.0, 1.0}};
 static const GLUvec4 x_axis = {{1.0, 0.0, 0.0, 1.0}};
 static const GLUvec4 y_axis = {{0.0, 1.0, 0.0, 1.0}};
 static const GLUvec4 z_axis = {{0.0, 0.0, 1.0, 1.0}};
diff --git a/shadow_map.c b/shadow_map.c
index 59e7650..a0df0ee 100644
--- a/shadow_map.c
+++ b/shadow_map.c
@@ -49,6 +49,8 @@ calculate_light_projection(void)
 {
 	GLUvec4 light_up;
 	GLUmat4 temp;
+	GLUvec4 light_to_rings;
+	float light_distance_to_rings;
 
 	/* Wrong.  So wrong. */
 	light_up.values[0] = 1.0;
@@ -61,6 +63,16 @@ calculate_light_projection(void)
 	print_GLUvec4("ring_center", &ring_bounding_sphere_center_world);
 	print_GLUvec4("light_up   ", &light_up);
 	*/
+
+	/* Our shadow mapping can't handle lights inside the frustum of the
+	 * shadow casters.
+	 */
+	gluSub4v_4v(&light_to_rings,
+		    &ring_bounding_sphere_center_world, &light_world);
+	light_distance_to_rings = gluLength4v(&light_to_rings);
+
+	assert(light_distance_to_rings > ring_bounding_sphere_radius);
+
 	/* Transform for looking from they eye's point of view at the pile of
 	 * rings.
 	 */