Implement sky spheres.

21 files changed, 362 insertions, 29 deletions

diff --git a/dimension/common.terminals b/dimension/common.terminals
index 5a0d778..4e8e6d1 100644
--- a/dimension/common.terminals
+++ b/dimension/common.terminals
@@ -394,7 +394,7 @@
 %token DMNSN_T_SINH                     "sinh"
 %token DMNSN_T_SIZE
 %token DMNSN_T_SKY                      "sky"
-%token DMNSN_T_SKY_SPHERE
+%token DMNSN_T_SKY_SPHERE               "sky_sphere"
 %token DMNSN_T_SLICE
 %token DMNSN_T_SLOPE
 %token DMNSN_T_SLOPE_MAP
diff --git a/dimension/grammar.epilogue b/dimension/grammar.epilogue
index 0eace5e..77a782a 100644
--- a/dimension/grammar.epilogue
+++ b/dimension/grammar.epilogue
@@ -126,6 +126,7 @@ dmnsn_astnode_string(dmnsn_astnode_type astnode_type)
   dmnsn_astnode_map(DMNSN_AST_MAX_TRACE_LEVEL,   "max_trace_level");
 
   dmnsn_astnode_map(DMNSN_AST_BACKGROUND, "background");
+  dmnsn_astnode_map(DMNSN_AST_SKY_SPHERE, "sky_sphere");
 
   dmnsn_astnode_map(DMNSN_AST_CAMERA,      "camera");
   dmnsn_astnode_map(DMNSN_AST_PERSPECTIVE, "perspective");
diff --git a/dimension/grammar.nonterminals b/dimension/grammar.nonterminals
index 9ab8ee1..912b660 100644
--- a/dimension/grammar.nonterminals
+++ b/dimension/grammar.nonterminals
@@ -31,3 +31,5 @@
 /* Atmospheric effects */
 %type <astnode> ATMOSPHERIC_EFFECT
 %type <astnode> BACKGROUND
+%type <astnode> SKY_SPHERE
+%type <astnode> SKY_SPHERE_ITEMS
diff --git a/dimension/grammar.rules b/dimension/grammar.rules
index 0e9d6f1..8b110c0 100644
--- a/dimension/grammar.rules
+++ b/dimension/grammar.rules
@@ -94,9 +94,31 @@ GLOBAL_CHARSET: "ascii" {
 /* Atmospheric effects */
 
 ATMOSPHERIC_EFFECT: BACKGROUND
+                  | SKY_SPHERE
 ;
 
 BACKGROUND: "background" "{" COLOR "}" {
             $$ = dmnsn_new_astnode1(DMNSN_AST_BACKGROUND, @$, $3);
           }
 ;
+
+SKY_SPHERE: "sky_sphere" "{"
+              SKY_SPHERE_ITEMS
+            "}"
+          {
+            $$ = $3;
+          }
+;
+
+SKY_SPHERE_ITEMS: /* empty */ {
+                  $$ = dmnsn_new_astnode(DMNSN_AST_SKY_SPHERE, @$);
+                }
+                | SKY_SPHERE_ITEMS PIGMENT {
+                  $$ = $1;
+                  dmnsn_array_push($$.children, &$2);
+                }
+                | SKY_SPHERE_ITEMS TRANSFORMATION {
+                  $$ = $1;
+                  dmnsn_array_push($$.children, &$2);
+                }
+;
diff --git a/dimension/lexer.l b/dimension/lexer.l
index 5e1afa2..c5eeca7 100644
--- a/dimension/lexer.l
+++ b/dimension/lexer.l
@@ -258,6 +258,7 @@ unsigned long wchar;
 "sin"                   RETURN_TOKEN(DMNSN_T_SIN);
 "sinh"                  RETURN_TOKEN(DMNSN_T_SINH);
 "sky"                   RETURN_TOKEN(DMNSN_T_SKY);
+"sky_sphere"            RETURN_TOKEN(DMNSN_T_SKY_SPHERE);
 "sphere"                RETURN_TOKEN(DMNSN_T_SPHERE);
 "sqrt"                  RETURN_TOKEN(DMNSN_T_SQRT);
 "strcmp"                RETURN_TOKEN(DMNSN_T_STRCMP);
diff --git a/dimension/parse.h b/dimension/parse.h
index 38e4eef..7bff5ba 100644
--- a/dimension/parse.h
+++ b/dimension/parse.h
@@ -40,6 +40,7 @@ typedef enum {
   DMNSN_AST_MAX_INTERSECTIONS,
 
   DMNSN_AST_BACKGROUND,
+  DMNSN_AST_SKY_SPHERE,
 
   DMNSN_AST_CAMERA,
   DMNSN_AST_PERSPECTIVE,
diff --git a/dimension/realize.c b/dimension/realize.c
index d4b45cb..2f74ce0 100644
--- a/dimension/realize.c
+++ b/dimension/realize.c
@@ -680,6 +680,37 @@ dmnsn_realize_pigment(dmnsn_astnode astnode)
   return pigment;
 }
 
+static dmnsn_sky_sphere *
+dmnsn_realize_sky_sphere(dmnsn_astnode astnode)
+{
+  dmnsn_assert(astnode.type == DMNSN_AST_SKY_SPHERE, "Expected a sky sphere.");
+
+  dmnsn_sky_sphere *sky_sphere = dmnsn_new_sky_sphere();
+
+  DMNSN_ARRAY_FOREACH (dmnsn_astnode *, item, astnode.children) {
+    switch (item->type) {
+    case DMNSN_AST_PIGMENT:
+      {
+        dmnsn_pigment *pigment = dmnsn_realize_pigment(*item);
+        dmnsn_array_push(sky_sphere->pigments, &pigment);
+        break;
+      }
+
+    case DMNSN_AST_TRANSFORMATION:
+      sky_sphere->trans = dmnsn_matrix_mul(
+        dmnsn_realize_transformation(*item),
+        sky_sphere->trans
+      );
+      break;
+
+    default:
+      dmnsn_assert(false, "Invalid sky sphere item.");
+    }
+  }
+
+  return sky_sphere;
+}
+
 static dmnsn_finish *
 dmnsn_realize_reflection(dmnsn_astnode astnode)
 {
@@ -1295,6 +1326,10 @@ dmnsn_realize_astree(const dmnsn_astree *astree)
       dmnsn_array_get(astnode->children, 0, &child);
       scene->background = dmnsn_realize_color(child);
       break;
+    case DMNSN_AST_SKY_SPHERE:
+      dmnsn_delete_sky_sphere(scene->sky_sphere);
+      scene->sky_sphere = dmnsn_realize_sky_sphere(*astnode);
+      break;
 
     case DMNSN_AST_CAMERA:
       dmnsn_delete_camera(scene->camera);
diff --git a/libdimension/Makefile.am b/libdimension/Makefile.am
index 542e684..86caa57 100644
--- a/libdimension/Makefile.am
+++ b/libdimension/Makefile.am
@@ -47,6 +47,7 @@ nobase_include_HEADERS = dimension.h                                           \
                          dimension/progress.h                                  \
                          dimension/raytrace.h                                  \
                          dimension/scene.h                                     \
+                         dimension/sky_sphere.h                                \
                          dimension/texture.h                                   \
                          dimension/timer.h
 
@@ -90,6 +91,7 @@ libdimension_la_SOURCES = $(nobase_include_HEADERS)                            \
                           raytrace.c                                           \
                           reflective.c                                         \
                           scene.c                                              \
+                          sky_sphere.c                                         \
                           solid_pigment.c                                      \
                           sphere.c                                             \
                           texture.c                                            \
diff --git a/libdimension/color.c b/libdimension/color.c
index e91ebc1..6d2078f 100644
--- a/libdimension/color.c
+++ b/libdimension/color.c
@@ -46,6 +46,13 @@ const dmnsn_color dmnsn_white = {
   .filter = 0.0,
   .trans  = 0.0
 };
+const dmnsn_color dmnsn_clear = {
+  .R = 0.0,
+  .G = 0.0,
+  .B = 0.0,
+  .filter = 0.0,
+  .trans  = 1.0
+};
 const dmnsn_color dmnsn_red = {
   .R = 1.0,
   .G = 0.0,
diff --git a/libdimension/dimension.h b/libdimension/dimension.h
index 55b3b87..d4ce61e 100644
--- a/libdimension/dimension.h
+++ b/libdimension/dimension.h
@@ -79,6 +79,7 @@ typedef void dmnsn_free_fn(void *ptr);
 #include <dimension/lights.h>
 #include <dimension/camera.h>
 #include <dimension/cameras.h>
+#include <dimension/sky_sphere.h>
 #include <dimension/scene.h>
 #include <dimension/raytrace.h>
 
diff --git a/libdimension/dimension/color.h b/libdimension/dimension/color.h
index 26ab4bb..e214b66 100644
--- a/libdimension/dimension/color.h
+++ b/libdimension/dimension/color.h
@@ -79,6 +79,7 @@ typedef struct {
 /* Standard colors */
 extern const dmnsn_color dmnsn_black;   /**< Black.   */
 extern const dmnsn_color dmnsn_white;   /**< White.   */
+extern const dmnsn_color dmnsn_clear;   /**< Clear.   */
 extern const dmnsn_color dmnsn_red;     /**< Red.     */
 extern const dmnsn_color dmnsn_green;   /**< Green.   */
 extern const dmnsn_color dmnsn_blue;    /**< Blue.    */
diff --git a/libdimension/dimension/scene.h b/libdimension/dimension/scene.h
index 489e4e5..0889359 100644
--- a/libdimension/dimension/scene.h
+++ b/libdimension/dimension/scene.h
@@ -45,6 +45,7 @@ typedef struct dmnsn_scene {
   /* World attributes */
   dmnsn_color background;         /**< Background color. */
   dmnsn_color ambient;            /**< Global ambient color. */
+  dmnsn_sky_sphere *sky_sphere;   /**< Sky sphere. */
   dmnsn_texture *default_texture; /**< Default object texture. */
 
   /** Camera. */
@@ -85,4 +86,10 @@ dmnsn_scene *dmnsn_new_scene(void);
  */
 void dmnsn_delete_scene(dmnsn_scene *scene);
 
+/**
+ * Initialize a scene.
+ * @param[in,out] scene  The scene to initalize.
+ */
+void dmnsn_scene_init(dmnsn_scene *scene);
+
 #endif /* DIMENSION_SCENE_H */
diff --git a/libdimension/dimension/sky_sphere.h b/libdimension/dimension/sky_sphere.h
new file mode 100644
index 0000000..5edacb0
--- /dev/null
+++ b/libdimension/dimension/sky_sphere.h
@@ -0,0 +1,63 @@
+/*************************************************************************
+ * Copyright (C) 2010 Tavian Barnes <tavianator@gmail.com>               *
+ *                                                                       *
+ * This file is part of The Dimension Library.                           *
+ *                                                                       *
+ * The Dimension Library is free software; you can redistribute it and/  *
+ * or modify it under the terms of the GNU Lesser General Public License *
+ * as published by the Free Software Foundation; either version 3 of the *
+ * License, or (at your option) any later version.                       *
+ *                                                                       *
+ * The Dimension Library is distributed in the hope that it will be      *
+ * useful, but WITHOUT ANY WARRANTY; without even the implied warranty   *
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  *
+ * Lesser General Public License for more details.                       *
+ *                                                                       *
+ * You should have received a copy of the GNU Lesser General Public      *
+ * License along with this program.  If not, see                         *
+ * <http://www.gnu.org/licenses/>.                                       *
+ *************************************************************************/
+
+/**
+ * @file
+ * Sky spheres.
+ */
+
+#ifndef DIMENSION_SKY_SPHERE_H
+#define DIMENSION_SKY_SPHERE_H
+
+/** A sky sphere. */
+typedef struct dmnsn_sky_sphere {
+  /** An array of pigments in inside-to-outside order. */
+  dmnsn_array *pigments;
+  dmnsn_matrix trans;
+} dmnsn_sky_sphere;
+
+/**
+ * Create a sky sphere.
+ * @return A new blank sky sphere.
+ */
+dmnsn_sky_sphere *dmnsn_new_sky_sphere();
+
+/**
+ * Delete a sky sphere.
+ * @param[in,out] sky_sphere  The sky sphere to delete.
+ */
+void dmnsn_delete_sky_sphere(dmnsn_sky_sphere *sky_sphere);
+
+/**
+ * Initialize a sky sphere.
+ * @param[in,out] sky_sphere  The sky sphere to initialize.
+ */
+void dmnsn_sky_sphere_init(dmnsn_sky_sphere *sky_sphere);
+
+/**
+ * Evaluate the color of the sky sphere.
+ * @param[in] sky_sphere  The sky sphere to evaluate.
+ * @param[in] d           The direction to look.
+ * @return The color of the sky in the direction of \p d.
+ */
+dmnsn_color dmnsn_sky_sphere_color(const dmnsn_sky_sphere *sky_sphere,
+                                   dmnsn_vector d);
+
+#endif /* DIMENSION_SKY_SPHERE_H */
diff --git a/libdimension/raytrace.c b/libdimension/raytrace.c
index e6596e4..3534331 100644
--- a/libdimension/raytrace.c
+++ b/libdimension/raytrace.c
@@ -77,13 +77,11 @@ dmnsn_raytrace_scene_thread(void *ptr)
 {
   dmnsn_raytrace_payload *payload = ptr;
 
+  /* Pre-calculate bounding box transformations, etc. */
+  dmnsn_scene_init(payload->scene);
+
   /* Time the bounding tree construction */
   payload->scene->bounding_timer = dmnsn_new_timer();
-    /* Pre-calculate bounding box transformations, etc. */
-    DMNSN_ARRAY_FOREACH (dmnsn_object **, object, payload->scene->objects) {
-      dmnsn_object_init(*object);
-    }
-
     payload->prtree = dmnsn_new_prtree(payload->scene->objects);
   dmnsn_complete_timer(payload->scene->bounding_timer);
 
@@ -210,21 +208,16 @@ dmnsn_raytrace_scene_impl(dmnsn_progress *progress, dmnsn_scene *scene,
   /* Iterate through each pixel */
   for (size_t y = index; y < scene->canvas->height; y += threads) {
     for (size_t x = 0; x < scene->canvas->width; ++x) {
-      /* Set the pixel to the background color */
-      dmnsn_color color = scene->background;
-
-      if (scene->quality) {
-        /* Get the ray corresponding to the (x,y)'th pixel */
-        dmnsn_line ray = dmnsn_camera_ray(
-          scene->camera,
-          ((double)x)/(scene->canvas->width - 1),
-          ((double)y)/(scene->canvas->height - 1)
-        );
+      /* Get the ray corresponding to the (x,y)'th pixel */
+      dmnsn_line ray = dmnsn_camera_ray(
+        scene->camera,
+        ((double)x)/(scene->canvas->width - 1),
+        ((double)y)/(scene->canvas->height - 1)
+      );
 
-        /* Shoot a ray */
-        state.reclevel = scene->reclimit;
-        color = dmnsn_raytrace_shoot(&state, ray);
-      }
+      /* Shoot a ray */
+      state.reclevel = scene->reclimit;
+      dmnsn_color color = dmnsn_raytrace_shoot(&state, ray);
 
       dmnsn_set_pixel(scene->canvas, x, y, color);
     }
@@ -272,6 +265,22 @@ dmnsn_raytrace_scene_impl(dmnsn_progress *progress, dmnsn_scene *scene,
    ? (state)->intersection->interior->ior       \
    : 1.0)
 
+/** Calculate the background color. */
+static dmnsn_color
+dmnsn_raytrace_background(dmnsn_raytrace_state *state, dmnsn_line ray)
+{
+  dmnsn_color color = state->scene->background;
+  if (state->scene->sky_sphere
+      && (state->scene->quality & DMNSN_RENDER_PIGMENT))
+  {
+    dmnsn_color sky = dmnsn_sky_sphere_color(state->scene->sky_sphere,
+                                             dmnsn_vector_normalize(ray.n));
+    color = dmnsn_color_add(dmnsn_color_filter(color, sky), sky);
+  }
+
+  return color;
+}
+
 /** Calculate the base pigment at the intersection. */
 static void
 dmnsn_raytrace_pigment(dmnsn_raytrace_state *state)
@@ -465,12 +474,11 @@ dmnsn_raytrace_shoot(dmnsn_raytrace_state *state, dmnsn_line ray)
     return dmnsn_black;
   --state->reclevel;
 
-  dmnsn_intersection intersection;
-  bool intersected
-    = dmnsn_prtree_intersection(state->prtree, ray, &intersection);
+  /* Calculate the background color */
+  dmnsn_color color = dmnsn_raytrace_background(state, ray);
 
-  dmnsn_color color = state->scene->background;
-  if (intersected) {
+  dmnsn_intersection intersection;
+  if (dmnsn_prtree_intersection(state->prtree, ray, &intersection)) {
     state->intersection = &intersection;
     state->r = dmnsn_line_point(state->intersection->ray,
                                 state->intersection->t);
diff --git a/libdimension/scene.c b/libdimension/scene.c
index 9eca7b7..c43a93a 100644
--- a/libdimension/scene.c
+++ b/libdimension/scene.c
@@ -34,6 +34,7 @@ dmnsn_new_scene()
 
   scene->background      = dmnsn_black;
   scene->ambient         = dmnsn_white;
+  scene->sky_sphere      = NULL;
   scene->default_texture = dmnsn_new_texture();
   scene->camera          = NULL;
   scene->canvas          = NULL;
@@ -68,6 +69,19 @@ dmnsn_delete_scene(dmnsn_scene *scene)
     dmnsn_delete_canvas(scene->canvas);
     dmnsn_delete_camera(scene->camera);
     dmnsn_delete_texture(scene->default_texture);
+    dmnsn_delete_sky_sphere(scene->sky_sphere);
     dmnsn_free(scene);
   }
 }
+
+void
+dmnsn_scene_init(dmnsn_scene *scene)
+{
+  if (scene->sky_sphere) {
+    dmnsn_sky_sphere_init(scene->sky_sphere);
+  }
+
+  DMNSN_ARRAY_FOREACH (dmnsn_object **, object, scene->objects) {
+    dmnsn_object_init(*object);
+  }
+}
diff --git a/libdimension/sky_sphere.c b/libdimension/sky_sphere.c
new file mode 100644
index 0000000..bb38c16
--- /dev/null
+++ b/libdimension/sky_sphere.c
@@ -0,0 +1,72 @@
+/*************************************************************************
+ * Copyright (C) 2009-2010 Tavian Barnes <tavianator@gmail.com>          *
+ *                                                                       *
+ * This file is part of The Dimension Library.                           *
+ *                                                                       *
+ * The Dimension Library is free software; you can redistribute it and/  *
+ * or modify it under the terms of the GNU Lesser General Public License *
+ * as published by the Free Software Foundation; either version 3 of the *
+ * License, or (at your option) any later version.                       *
+ *                                                                       *
+ * The Dimension Library is distributed in the hope that it will be      *
+ * useful, but WITHOUT ANY WARRANTY; without even the implied warranty   *
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  *
+ * Lesser General Public License for more details.                       *
+ *                                                                       *
+ * You should have received a copy of the GNU Lesser General Public      *
+ * License along with this program.  If not, see                         *
+ * <http://www.gnu.org/licenses/>.                                       *
+ *************************************************************************/
+
+/**
+ * @file
+ * Sky spheres.
+ */
+
+#include "dimension.h"
+
+dmnsn_sky_sphere *
+dmnsn_new_sky_sphere()
+{
+  dmnsn_sky_sphere *sky_sphere = dmnsn_malloc(sizeof(dmnsn_sky_sphere));
+  sky_sphere->pigments = dmnsn_new_array(sizeof(dmnsn_pigment *));
+  sky_sphere->trans = dmnsn_identity_matrix();
+  return sky_sphere;
+}
+
+void
+dmnsn_delete_sky_sphere(dmnsn_sky_sphere *sky_sphere)
+{
+  if (sky_sphere) {
+    DMNSN_ARRAY_FOREACH (dmnsn_pigment **, pigment, sky_sphere->pigments) {
+      dmnsn_delete_pigment(*pigment);
+    }
+    dmnsn_free(sky_sphere);
+  }
+}
+
+void
+dmnsn_sky_sphere_init(dmnsn_sky_sphere *sky_sphere)
+{
+  DMNSN_ARRAY_FOREACH (dmnsn_pigment **, pigment, sky_sphere->pigments) {
+    (*pigment)->trans = dmnsn_matrix_mul(sky_sphere->trans, (*pigment)->trans);
+    dmnsn_pigment_init(*pigment);
+  }
+}
+
+dmnsn_color
+dmnsn_sky_sphere_color(const dmnsn_sky_sphere *sky_sphere, dmnsn_vector d)
+{
+  dmnsn_color color = dmnsn_black;
+  color.trans = 1.0;
+
+  DMNSN_ARRAY_FOREACH (const dmnsn_pigment **, pigment, sky_sphere->pigments) {
+    dmnsn_pigment_fn *pigment_fn = (*pigment)->pigment_fn;
+    if (pigment_fn) {
+      dmnsn_color sky = (*pigment_fn)(*pigment, d);
+      color = dmnsn_color_add(dmnsn_color_filter(color, sky), sky);
+    }
+  }
+
+  return color;
+}
diff --git a/tests/dimension/demo.pov b/tests/dimension/demo.pov
index 0740ecb..8088f45 100644
--- a/tests/dimension/demo.pov
+++ b/tests/dimension/demo.pov
@@ -29,7 +29,17 @@ camera {
 }
 
 background {
-  color rgbf <0, 0.1, 0.2, 0.1>
+  color transmit 1
+}
+
+sky_sphere {
+  pigment {
+    gradient y
+    color_map {
+      [0.0   color rgb <1, 0.5, 0>]
+      [0.35  color rgbf <0, 0.1, 0.2, 0.1>]
+    }
+  }
 }
 
 light_source {
diff --git a/tests/dimension/demo.sh b/tests/dimension/demo.sh
index 4e26bdc..a741268 100755
--- a/tests/dimension/demo.sh
+++ b/tests/dimension/demo.sh
@@ -32,7 +32,22 @@ demo_exp=$(echo -n \
       (rotation (vector (integer 0) (integer 53) (integer 0)
                         (integer 0) (integer 0)))))
   (background
-    (vector (integer 0) (float 0.1) (float 0.2) (float 0.1) (integer 0)))
+    (vector (integer 0) (integer 0) (integer 0) (integer 0) (integer 1)))
+  (sky_sphere
+    (pigment
+      (pattern
+        (gradient (vector (integer 0) (integer 1)
+                  (integer 0) (integer 0) (integer 0))))
+      (pigment-modifiers
+        (color_map
+          (color_map-entry
+            (float 0)
+            (vector (integer 1) (float 0.5) (integer 0)
+                    (integer 0) (integer 0)))
+          (color_map-entry
+            (float 0.35)
+            (vector (integer 0) (float 0.1) (float 0.2)
+                    (float 0.1) (integer 0)))))))
   (light_source
     (vector (integer -15) (integer 20) (integer 10) (integer 0) (integer 0))
     (vector (integer 1) (integer 1) (integer 1) (integer 0) (integer 0))
diff --git a/tests/dimension/integer-overflow.pov b/tests/dimension/integer-overflow.pov
new file mode 100644
index 0000000..670d659
--- /dev/null
+++ b/tests/dimension/integer-overflow.pov
@@ -0,0 +1,25 @@
+/*************************************************************************
+ * Copyright (C) 2009-2010 Tavian Barnes <tavianator@gmail.com>          *
+ *                                                                       *
+ * This file is part of The Dimension Test Suite.                        *
+ *                                                                       *
+ * The Dimension Test Suite is free software; you can redistribute it    *
+ * and/or modify it under the terms of the GNU General Public License as *
+ * published by the Free Software Foundation; either version 3 of the    *
+ * License, or (at your option) any later version.                       *
+ *                                                                       *
+ * The Dimension Test Suite is distributed in the hope that it will be   *
+ * useful, but WITHOUT ANY WARRANTY; without even the implied warranty   *
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  *
+ * General Public License for more details.                              *
+ *                                                                       *
+ * You should have received a copy of the GNU General Public License     *
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
+ *************************************************************************/
+
+// Test integer overflow handling -- overflows should convert to floats
+
+torus {
+  10000000000000000000,
+  abs(-2147483647 - 1)*abs(-9223372036854775807 - 1)*((-2147483647 - 2)*(2147483647 + 1))*((-9223372036854775807.0 - 2)*(9223372036854775807.0 + 1))*(65536*65536)*(4294967296*4294967296.0)
+}
diff --git a/tests/dimension/integer-overflow.sh b/tests/dimension/integer-overflow.sh
new file mode 100755
index 0000000..737c0e2
--- /dev/null
+++ b/tests/dimension/integer-overflow.sh
@@ -0,0 +1,35 @@
+#!/bin/sh
+
+#########################################################################
+# Copyright (C) 2009-2010 Tavian Barnes <tavianator@gmail.com>          #
+#                                                                       #
+# This file is part of The Dimension Test Suite.                        #
+#                                                                       #
+# The Dimension Test Suite is free software; you can redistribute it    #
+# and/or modify it under the terms of the GNU General Public License as #
+# published by the Free Software Foundation; either version 3 of the    #
+# License, or (at your option) any later version.                       #
+#                                                                       #
+# The Dimension Test Suite is distributed in the hope that it will be   #
+# useful, but WITHOUT ANY WARRANTY; without even the implied warranty   #
+# of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  #
+# General Public License for more details.                              #
+#                                                                       #
+# You should have received a copy of the GNU General Public License     #
+# along with this program.  If not, see <http://www.gnu.org/licenses/>. #
+#########################################################################
+
+integer_overflow=$(${top_builddir}/dimension/dimension --parse ${srcdir}/integer-overflow.pov)
+integer_overflow_exp="$(echo -n \
+'((object
+    (torus
+      (float 1e+19)
+      (float 6.15656e+113))
+    object-modifiers))' \
+| tr '\n' ' ' | sed -r 's/[[:space:]]+/ /g')"
+
+if [ "$integer_overflow" != "$integer_overflow_exp" ]; then
+  echo "integer-overflow.pov parsed as \"$integer_overflow\"" >&2
+  echo "                   -- expected \"$integer_overflow_exp\"" >&2
+  exit 1
+fi
diff --git a/tests/libdimension/render.c b/tests/libdimension/render.c
index 440333c..31518bf 100644
--- a/tests/libdimension/render.c
+++ b/tests/libdimension/render.c
@@ -66,8 +66,19 @@ dmnsn_new_test_scene(void)
   scene->camera->trans = trans;
 
   /* Background color */
-  scene->background = dmnsn_color_from_sRGB((dmnsn_sRGB){ 0.0, 0.1, 0.2 });
-  scene->background.filter = 0.1;
+  scene->background = dmnsn_clear;
+
+  /* Sky sphere */
+  scene->sky_sphere = dmnsn_new_sky_sphere();
+  dmnsn_pattern *sky_gradient = dmnsn_new_gradient_pattern(dmnsn_y);
+  dmnsn_color_map *sky_gradient_color_map = dmnsn_new_color_map();
+  dmnsn_add_color_map_entry(sky_gradient_color_map, 0.0, dmnsn_orange);
+  dmnsn_color background = dmnsn_color_from_sRGB((dmnsn_sRGB){ 0.0, 0.1, 0.2 });
+  background.filter = 0.1;
+  dmnsn_add_color_map_entry(sky_gradient_color_map, 0.35, background);
+  dmnsn_pigment *sky_pigment
+    = dmnsn_new_color_map_pigment(sky_gradient, sky_gradient_color_map);
+  dmnsn_array_push(scene->sky_sphere->pigments, &sky_pigment);
 
   /* Light source */
   dmnsn_light *light = dmnsn_new_point_light(