From 5c73e21b426ed381a1ae8d1bcac6fc78e5952b8f Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@gmail.com>
Date: Sun, 14 Jun 2009 18:18:19 +0000
Subject: Add a transformation matrix to objects.

---
 libdimension/dimension/object.h |  3 +++
 libdimension/object.c           |  6 +++++-
 libdimension/raytrace.c         | 10 +++++++---
 tests/raytrace.c                |  1 +
 4 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/libdimension/dimension/object.h b/libdimension/dimension/object.h
index bd660a0..589ac29 100644
--- a/libdimension/dimension/object.h
+++ b/libdimension/dimension/object.h
@@ -38,6 +38,9 @@ struct dmnsn_object {
   /* Generic pointer for object info */
   void *ptr;
 
+  /* Transformation matrix */
+  dmnsn_matrix trans;
+
   /* Callback functions */
   dmnsn_object_intersections_fn *intersections_fn;
   dmnsn_object_inside_fn        *inside_fn;
diff --git a/libdimension/object.c b/libdimension/object.c
index 39064f3..75a82b6 100644
--- a/libdimension/object.c
+++ b/libdimension/object.c
@@ -24,7 +24,11 @@
 dmnsn_object *
 dmnsn_new_object()
 {
-  return malloc(sizeof(dmnsn_object));
+  dmnsn_object *object = malloc(sizeof(dmnsn_object));
+  if (object) {
+    object->trans = dmnsn_identity_matrix();
+  }
+  return object;
 }
 
 void
diff --git a/libdimension/raytrace.c b/libdimension/raytrace.c
index 469ac66..316157a 100644
--- a/libdimension/raytrace.c
+++ b/libdimension/raytrace.c
@@ -68,7 +68,7 @@ dmnsn_raytrace_scene_thread(void *arg)
 {
   unsigned int i, j, k;
   dmnsn_object *object;
-  dmnsn_line ray;
+  dmnsn_line ray, ray_trans;
   dmnsn_raytrace_thread_payload *payload = (dmnsn_raytrace_thread_payload *)arg;
   dmnsn_scene *scene = payload->scene;
   dmnsn_array *intersections;
@@ -83,11 +83,15 @@ dmnsn_raytrace_scene_thread(void *arg)
 
         /* Get the ray corresponding to the (i,j)th pixel */
         ray = (*scene->camera->ray_fn)(scene->camera, scene->canvas, i, j);
-        
+
         for (k = 0; k < scene->objects->length; ++k) {
           dmnsn_array_get(scene->objects, k, &object);
+
+          /* Transform the ray according to the object */
+          ray_trans = dmnsn_matrix_line_mul(object->trans, ray);
+
           /* Test for an intersection with an object */
-          intersections = (*object->intersections_fn)(object, ray);
+          intersections = (*object->intersections_fn)(object, ray_trans);
           if (intersections->length > 0) {
             /* Mark intersections white */
             dmnsn_set_pixel(scene->canvas, i, j,
diff --git a/tests/raytrace.c b/tests/raytrace.c
index de1bc89..ec13782 100644
--- a/tests/raytrace.c
+++ b/tests/raytrace.c
@@ -59,6 +59,7 @@ int main() {
   scene->background = color;
 
   cube = dmnsn_new_cube();
+  cube->trans = dmnsn_rotation_matrix(dmnsn_vector_construct(0.75, 0.0, 0.0));
   dmnsn_array_push(scene->objects, &cube);
 
   dmnsn_raytrace_scene(scene);
-- 
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