From 89da144e4095ecece603a5d7adf29b7a8e493bb1 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@gmail.com>
Date: Mon, 9 Nov 2009 14:18:38 -0500
Subject: Store inverse object transformation in a separate field.

---
 dimension/realize.c             |  2 --
 libdimension/dimension/object.h |  2 +-
 libdimension/kD_splay_tree.c    | 25 +++++++++++++------------
 tests/libdimension/tests.c      |  8 ++------
 4 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/dimension/realize.c b/dimension/realize.c
index b5c4225..bb977a6 100644
--- a/dimension/realize.c
+++ b/dimension/realize.c
@@ -113,7 +113,6 @@ dmnsn_realize_box(dmnsn_astnode astnode)
                                                     (x2.z + x1.z)/2.0)),
     box->trans
   );
-  box->trans = dmnsn_matrix_inverse(box->trans);
 
   return box;
 }
@@ -151,7 +150,6 @@ dmnsn_realize_sphere(dmnsn_astnode astnode)
 
   sphere->trans = dmnsn_scale_matrix(dmnsn_vector_construct(r, r, r));
   sphere->trans = dmnsn_matrix_mul(dmnsn_translation_matrix(x0), sphere->trans);
-  sphere->trans = dmnsn_matrix_inverse(sphere->trans);
 
   return sphere;
 }
diff --git a/libdimension/dimension/object.h b/libdimension/dimension/object.h
index fd0eba1..0f53406 100644
--- a/libdimension/dimension/object.h
+++ b/libdimension/dimension/object.h
@@ -56,7 +56,7 @@ struct dmnsn_object {
   dmnsn_texture *texture;
 
   /* Transformation matrix */
-  dmnsn_matrix trans;
+  dmnsn_matrix trans, trans_inv;
 
   /* Bounding box */
   dmnsn_vector min, max;
diff --git a/libdimension/kD_splay_tree.c b/libdimension/kD_splay_tree.c
index 44fae7b..5c6289d 100644
--- a/libdimension/kD_splay_tree.c
+++ b/libdimension/kD_splay_tree.c
@@ -98,10 +98,11 @@ static void dmnsn_kD_splay_node_swallow(dmnsn_kD_splay_node *node,
 void
 dmnsn_kD_splay_insert(dmnsn_kD_splay_tree *tree, dmnsn_object *object)
 {
-  dmnsn_vector corner;
-  dmnsn_matrix trans_inv;
   dmnsn_kD_splay_node *node = dmnsn_new_kD_splay_node(), *parent = tree->root;
 
+  /* Store the inverse of the transformation matrix */
+  object->trans_inv = dmnsn_matrix_inverse(object->trans);
+
   node->contains = NULL;
   node->container = NULL;
   node->parent = NULL;
@@ -110,36 +111,36 @@ dmnsn_kD_splay_insert(dmnsn_kD_splay_tree *tree, dmnsn_object *object)
   /* Calculate the new bounding box by finding the minimum coordinate of the
      transformed corners of the object's original bounding box */
 
-  trans_inv = dmnsn_matrix_inverse(object->trans);
-  node->min = dmnsn_matrix_vector_mul(trans_inv, object->min);
+  node->min = dmnsn_matrix_vector_mul(object->trans, object->min);
   node->max = node->min;
 
+  dmnsn_vector corner;
   corner = dmnsn_vector_construct(object->min.x, object->min.y, object->max.z);
-  corner = dmnsn_matrix_vector_mul(trans_inv, corner);
+  corner = dmnsn_matrix_vector_mul(object->trans, corner);
   dmnsn_kD_splay_node_swallow(node, corner, corner);
 
   corner = dmnsn_vector_construct(object->min.x, object->max.y, object->min.z);
-  corner = dmnsn_matrix_vector_mul(trans_inv, corner);
+  corner = dmnsn_matrix_vector_mul(object->trans, corner);
   dmnsn_kD_splay_node_swallow(node, corner, corner);
 
   corner = dmnsn_vector_construct(object->min.x, object->max.y, object->max.z);
-  corner = dmnsn_matrix_vector_mul(trans_inv, corner);
+  corner = dmnsn_matrix_vector_mul(object->trans, corner);
   dmnsn_kD_splay_node_swallow(node, corner, corner);
 
   corner = dmnsn_vector_construct(object->max.x, object->min.y, object->min.z);
-  corner = dmnsn_matrix_vector_mul(trans_inv, corner);
+  corner = dmnsn_matrix_vector_mul(object->trans, corner);
   dmnsn_kD_splay_node_swallow(node, corner, corner);
 
   corner = dmnsn_vector_construct(object->max.x, object->min.y, object->max.z);
-  corner = dmnsn_matrix_vector_mul(trans_inv, corner);
+  corner = dmnsn_matrix_vector_mul(object->trans, corner);
   dmnsn_kD_splay_node_swallow(node, corner, corner);
 
   corner = dmnsn_vector_construct(object->max.x, object->max.y, object->min.z);
-  corner = dmnsn_matrix_vector_mul(trans_inv, corner);
+  corner = dmnsn_matrix_vector_mul(object->trans, corner);
   dmnsn_kD_splay_node_swallow(node, corner, corner);
 
   corner = dmnsn_vector_construct(object->max.x, object->max.y, object->max.z);
-  corner = dmnsn_matrix_vector_mul(trans_inv, corner);
+  corner = dmnsn_matrix_vector_mul(object->trans, corner);
   dmnsn_kD_splay_node_swallow(node, corner, corner);
 
   /* Now insert the node */
@@ -337,7 +338,7 @@ dmnsn_kD_splay_search_recursive(dmnsn_kD_splay_node *node, dmnsn_line ray,
       || dmnsn_ray_box_intersection(ray, node->min, node->max, t))
   {
     /* Transform the ray according to the object */
-    ray_trans = dmnsn_matrix_line_mul(node->object->trans, ray);
+    ray_trans = dmnsn_matrix_line_mul(node->object->trans_inv, ray);
 
     if (dmnsn_box_contains(ray_trans.x0, node->object->min, node->object->max)
         || dmnsn_ray_box_intersection(ray_trans, node->object->min,
diff --git a/tests/libdimension/tests.c b/tests/libdimension/tests.c
index 1257219..87cbb7b 100644
--- a/tests/libdimension/tests.c
+++ b/tests/libdimension/tests.c
@@ -86,9 +86,7 @@ dmnsn_new_default_scene()
     return NULL;
   }
 
-  sphere->trans = dmnsn_matrix_inverse(
-    dmnsn_scale_matrix(dmnsn_vector_construct(1.25, 1.25, 1.25))
-  );
+  sphere->trans = dmnsn_scale_matrix(dmnsn_vector_construct(1.25, 1.25, 1.25));
 
   dmnsn_object *cube = dmnsn_new_cube();
   if (!cube) {
@@ -109,9 +107,7 @@ dmnsn_new_default_scene()
     return NULL;
   }
 
-  cube->trans = dmnsn_matrix_inverse(
-    dmnsn_rotation_matrix(dmnsn_vector_construct(0.75, 0.0, 0.0))
-  );
+  cube->trans = dmnsn_rotation_matrix(dmnsn_vector_construct(0.75, 0.0, 0.0));
 
   /* Now make a light */
 
-- 
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