Save off the obj_to_world transforms for each ring.

1 files changed, 17 insertions, 5 deletions

diff --git a/glass.c b/glass.c
index ab214a8..9b31fc9 100644
--- a/glass.c
+++ b/glass.c
@@ -43,6 +43,7 @@
 
 #define DEFAULT_WIDTH	600
 #define DEFAULT_HEIGHT	700
+#define NUM_RINGS	27
 
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0]))
 
@@ -97,6 +98,7 @@ static GLUvec4 eye_center_world = {{0.0, 1.0, 2.0, 1.0}};
 static GLUvec4 light_eye;
 GLUmat4 projection;
 GLUmat4 world_to_eye;
+GLUmat4 ring_obj_to_world[NUM_RINGS];
 
 static time_t start_tv_sec = 0;
 static float start_time, cur_time, last_fps_time = 0;
@@ -187,12 +189,12 @@ do_ring_drawelements(void)
 }
 
 static void
-install_transform(int instance)
+calc_new_ring_transforms(int instance)
 {
 	int x_index = (instance / 3) / 3 - 1;
 	int y_index = (instance / 3) % 3 - 1;
 	int z_index = instance % 3;
-	GLUmat4 mv, mvp, obj_to_world, temp;
+	GLUmat4 obj_to_world, temp;
 
 	/* Have the ring spinning on its axis slowly. */
 	obj_to_world = gluRotate4v(&z_axis, cur_time * 2 * M_PI / 20);
@@ -221,10 +223,16 @@ install_transform(int instance)
 	temp = gluTranslate3(x_index * 5.0,
 			     10 + y_index * 5.0,
 			     7.0 + z_index * 5.0);
-	obj_to_world = gluMult4m_4m(&temp, &obj_to_world);
+	ring_obj_to_world[instance] = gluMult4m_4m(&temp, &obj_to_world);
+}
+
+static void
+install_transform(int instance)
+{
+	GLUmat4 mv, mvp;
 
 	/* Generate the whole mvp */
-	mv = gluMult4m_4m(&world_to_eye, &obj_to_world);
+	mv = gluMult4m_4m(&world_to_eye, &ring_obj_to_world[instance]);
 	mvp = gluMult4m_4m(&projection, &mv);
 
 	glUniformMatrix4fv(uniforms[UNIFORM_MV].location, 1, 0,
@@ -245,7 +253,7 @@ draw_rings(void)
 
 		glBindVertexArray(ring.array_obj);
 		glBindBuffer(GL_ELEMENT_ARRAY_BUFFER_ARB, ring.vbo);
-		for (instance = 0; instance < 27; instance++) {
+		for (instance = 0; instance < NUM_RINGS; instance++) {
 			install_transform(instance);
 			do_ring_drawelements();
 		}
@@ -255,6 +263,8 @@ draw_rings(void)
 static void
 draw(void)
 {
+	int instance;
+
 	glClearColor(0.0, 0.0, 0.8, 0.0);
 	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
@@ -262,6 +272,8 @@ draw(void)
 	glEnable(GL_DEPTH_TEST);
 
 	update_light_position();
+	for (instance = 0; instance < NUM_RINGS; instance++)
+		calc_new_ring_transforms(instance);
 
 	glViewport(0, 0, win_width, win_height);