Translucency support.

6 files changed, 137 insertions, 49 deletions

diff --git a/libdimension/color.c b/libdimension/color.c
index 0ec9e0b..f309d09 100644
--- a/libdimension/color.c
+++ b/libdimension/color.c
@@ -27,41 +27,61 @@ const dmnsn_CIE_XYZ dmnsn_whitepoint = { .X = 0.9504060171449392,
                                          .Z = 1.089062231497274 };
 
 /* Standard colors */
-const dmnsn_color dmnsn_black = { .X = 0.0, .Y = 0.0, .Z = 0.0 };
+const dmnsn_color dmnsn_black = {
+  .X = 0.0,
+  .Y = 0.0,
+  .Z = 0.0,
+  .filter = 0.0,
+  .trans  = 0.0
+};
 const dmnsn_color dmnsn_white = {
   .X = 0.9504060171449392,
   .Y = 0.9999085943425312,
-  .Z = 1.089062231497274
+  .Z = 1.089062231497274,
+  .filter = 0.0,
+  .trans  = 0.0
 };
 const dmnsn_color dmnsn_red = {
   .X = 0.4123808838268995,
   .Y = 0.2126198631048975,
-  .Z = 0.0193434956789248
+  .Z = 0.0193434956789248,
+  .filter = 0.0,
+  .trans  = 0.0
 };
 const dmnsn_color dmnsn_green = {
   .X = 0.3575728355732478,
   .Y = 0.7151387878413206,
-  .Z = 0.1192121694056356
+  .Z = 0.1192121694056356,
+  .filter = 0.0,
+  .trans  = 0.0
 };
 const dmnsn_color dmnsn_blue = {
   .X = 0.1804522977447919,
   .Y = 0.0721499433963131,
-  .Z = 0.950506566412713
+  .Z = 0.950506566412713,
+  .filter = 0.0,
+  .trans  = 0.0
 };
 const dmnsn_color dmnsn_magenta = {
   .X = 0.5928331815716914,
   .Y = 0.2847698065012106,
-  .Z = 0.9698500620916378
+  .Z = 0.9698500620916378,
+  .filter = 0.0,
+  .trans  = 0.0
 };
 const dmnsn_color dmnsn_yellow = {
   .X = 0.7699537194001473,
   .Y = 0.9277586509462181,
-  .Z = 0.1385556650845604
+  .Z = 0.1385556650845604,
+  .filter = 0.0,
+  .trans  = 0.0
 };
 const dmnsn_color dmnsn_cyan = {
   .X = 0.5380251333180397,
   .Y = 0.7872887312376337,
-  .Z = 1.069718735818349
+  .Z = 1.069718735818349,
+  .filter = 0.0,
+  .trans  = 0.0
 };
 
 /* Convert a CIE XYZ color to a dmnsn_color (actually a no-op) */
@@ -335,8 +355,10 @@ dmnsn_color_add(dmnsn_color color1, dmnsn_color color2)
 
   dmnsn_color ret = dmnsn_color_from_Lab(Lab, dmnsn_whitepoint);
   /* Weighted average of transparencies by intensity */
-  ret.filter = (Lab1.L*color1.filter + Lab2.L*color2.filter)/Lab.L;
-  ret.trans  = (Lab1.L*color1.trans  + Lab2.L*color2.trans)/Lab.L;
+  if (Lab.L) {
+    ret.filter = (Lab1.L*color1.filter + Lab2.L*color2.filter)/Lab.L;
+    ret.trans  = (Lab1.L*color1.trans  + Lab2.L*color2.trans)/Lab.L;
+  }
 
   return ret;
 }
@@ -357,6 +379,16 @@ dmnsn_color_mul(double n, dmnsn_color color)
   return ret;
 }
 
+/* Filters `color' through `filter' */
+dmnsn_color
+dmnsn_color_filter(dmnsn_color color, dmnsn_color filter)
+{
+  dmnsn_color transmitted = dmnsn_color_mul(filter.trans, color);
+  dmnsn_color filtered = dmnsn_color_mul(filter.filter,
+                                         dmnsn_color_illuminate(filter, color));
+  return dmnsn_color_add(transmitted, filtered);
+}
+
 /* Illuminates `color' with `light' */
 dmnsn_color
 dmnsn_color_illuminate(dmnsn_color light, dmnsn_color color)
diff --git a/libdimension/dimension/color.h b/libdimension/dimension/color.h
index ad50334..10fa1a7 100644
--- a/libdimension/dimension/color.h
+++ b/libdimension/dimension/color.h
@@ -90,6 +90,7 @@ dmnsn_sRGB    dmnsn_sRGB_from_color(dmnsn_color color);
 /* Perceptual color manipulation */
 dmnsn_color dmnsn_color_add(dmnsn_color color1, dmnsn_color color2);
 dmnsn_color dmnsn_color_mul(double n, dmnsn_color color);
+dmnsn_color dmnsn_color_filter(dmnsn_color color, dmnsn_color filter);
 dmnsn_color dmnsn_color_illuminate(dmnsn_color light, dmnsn_color color);
 double dmnsn_color_difference(dmnsn_color color1, dmnsn_color color2);
 
diff --git a/libdimension/dimension/scene.h b/libdimension/dimension/scene.h
index 8108b2b..25e52fe 100644
--- a/libdimension/dimension/scene.h
+++ b/libdimension/dimension/scene.h
@@ -31,6 +31,7 @@ typedef enum {
   DMNSN_RENDER_PIGMENT,
   DMNSN_RENDER_LIGHTS,
   DMNSN_RENDER_FINISH,
+  DMNSN_RENDER_TRANSLUCENCY,
   DMNSN_RENDER_FULL
 } dmnsn_quality;
 
diff --git a/libdimension/objects.c b/libdimension/objects.c
index b5e4a32..845edfa 100644
--- a/libdimension/objects.c
+++ b/libdimension/objects.c
@@ -73,6 +73,10 @@ dmnsn_sphere_intersection_fn(const dmnsn_object *sphere, dmnsn_line line)
       intersection->t       = t;
       intersection->normal  = dmnsn_line_point(line, t);
       intersection->texture = sphere->texture;
+
+      /* Flip the normal if we're inside the sphere */
+      if (dmnsn_vector_dot(line.n, intersection->normal) > 0.0)
+        intersection->normal = dmnsn_vector_negate(intersection->normal);
     }
   }
 
@@ -128,7 +132,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
         && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
     {
       t = t_temp;
-      normal = dmnsn_vector_construct(-1.0, 0.0, 0.0);
+      normal = dmnsn_vector_construct(-copysign(line.n.x, 1.0), 0.0, 0.0);
     }
 
     /* x = 1.0 */
@@ -138,7 +142,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
         && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
     {
       t = t_temp;
-      normal = dmnsn_vector_construct(1.0, 0.0, 0.0);
+      normal = dmnsn_vector_construct(-copysign(line.n.x, 1.0), 0.0, 0.0);
     }
   }
 
@@ -150,7 +154,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
         && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
     {
       t = t_temp;
-      normal = dmnsn_vector_construct(0.0, -1.0, 0.0);
+      normal = dmnsn_vector_construct(0.0, -copysign(line.n.y, 1.0), 0.0);
     }
 
     /* y = 1.0 */
@@ -160,7 +164,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
         && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
     {
       t = t_temp;
-      normal = dmnsn_vector_construct(0.0, 1.0, 0.0);
+      normal = dmnsn_vector_construct(0.0, -copysign(line.n.y, 1.0), 0.0);
     }
   }
 
@@ -172,7 +176,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
         && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
     {
       t = t_temp;
-      normal = dmnsn_vector_construct(0.0, 0.0, -1.0);
+      normal = dmnsn_vector_construct(0.0, 0.0, -copysign(line.n.z, 1.0));
     }
 
     /* z = 1.0 */
@@ -182,7 +186,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
         && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
     {
       t = t_temp;
-      normal = dmnsn_vector_construct(0.0, 0.0, 1.0);
+      normal = dmnsn_vector_construct(0.0, 0.0, -copysign(line.n.z, 1.0));
     }
   }
 
diff --git a/libdimension/png.c b/libdimension/png.c
index 20190d8..1ad8a1a 100644
--- a/libdimension/png.c
+++ b/libdimension/png.c
@@ -96,8 +96,14 @@ dmnsn_png_optimizer_fn(dmnsn_canvas *canvas, dmnsn_canvas_optimizer optimizer,
     pixel[2] = sRGB.B*UINT16_MAX;
   }
 
-  /* color.filter + color.trans is in [0.0, 1.0] by definition */
-  pixel[3] = (color.filter + color.trans)*UINT16_MAX;
+  double alpha = color.filter + color.trans;
+  if (alpha <= 0.0) {
+    pixel[3] = 0;
+  } else if (alpha >= 1.0) {
+    pixel[3] = UINT16_MAX;
+  } else {
+    pixel[3] = alpha*UINT16_MAX;
+  }
 }
 
 /* Payload to store function arguments for thread callbacks */
@@ -359,8 +365,14 @@ dmnsn_png_write_canvas_impl(dmnsn_progress *progress,
         row[4*x + 2] = sRGB.B*UINT16_MAX;
       }
 
-      /* color.filter + color.trans is in [0.0, 1.0] by definition */
-      row[4*x + 3] = (color.filter + color.trans)*UINT16_MAX;
+      double alpha = color.filter + color.trans;
+      if (alpha <= 0.0) {
+        row[4*x + 3] = 0;
+      } else if (alpha >= 1.0) {
+        row[4*x + 3] = UINT16_MAX;
+      } else {
+        row[4*x + 3] = alpha*UINT16_MAX;
+      }
     }
 
     /* Write the row */
diff --git a/libdimension/raytrace.c b/libdimension/raytrace.c
index 7608d85..1024a7e 100644
--- a/libdimension/raytrace.c
+++ b/libdimension/raytrace.c
@@ -316,28 +316,31 @@ dmnsn_raytrace_lighting(dmnsn_intersection *intersection, dmnsn_scene *scene,
     );
 
     /* Search for an object in the way of the light source */
-    dmnsn_intersection *shadow_caster
-      = dmnsn_kD_splay_search(kD_splay_tree, shadow_ray);
-    bool lit = !shadow_caster || shadow_caster->t > 1.0;
-    dmnsn_delete_intersection(shadow_caster);
-
-    if (scene->quality >= DMNSN_RENDER_FINISH && finish) {
-      dmnsn_color light_color = dmnsn_black;
-      if (lit)
-        light_color = (*light->light_fn)(light, x0);
-
-      dmnsn_vector ray    = dmnsn_vector_normalize(shadow_ray.n);
-      dmnsn_vector normal = intersection->normal;
-      dmnsn_vector viewer
-        = dmnsn_vector_normalize(dmnsn_vector_negate(intersection->ray.n));
-
-      /* Get this light's color contribution to the object */
-      dmnsn_color contrib = (*finish->finish_fn)(finish,
-                                                 light_color, color,
-                                                 ray, normal, viewer);
-      illum = dmnsn_color_add(contrib, illum);
-    } else if (lit) {
-      illum = color;
+    bool lit = dmnsn_vector_dot(shadow_ray.n, intersection->normal) > 0.0;
+    if (lit) {
+      dmnsn_intersection *shadow_caster
+        = dmnsn_kD_splay_search(kD_splay_tree, shadow_ray);
+      lit = (!shadow_caster || shadow_caster->t > 1.0);
+      dmnsn_delete_intersection(shadow_caster);
+    }
+
+    if (lit) {
+      if (scene->quality >= DMNSN_RENDER_FINISH && finish) {
+        dmnsn_color light_color = (*light->light_fn)(light, x0);
+
+        dmnsn_vector ray    = dmnsn_vector_normalize(shadow_ray.n);
+        dmnsn_vector normal = intersection->normal;
+        dmnsn_vector viewer
+          = dmnsn_vector_normalize(dmnsn_vector_negate(intersection->ray.n));
+
+        /* Get this light's color contribution to the object */
+        dmnsn_color contrib = (*finish->finish_fn)(finish,
+                                                   light_color, color,
+                                                   ray, normal, viewer);
+        illum = dmnsn_color_add(contrib, illum);
+      } else {
+        illum = color;
+      }
     }
   }
 
@@ -347,24 +350,59 @@ dmnsn_raytrace_lighting(dmnsn_intersection *intersection, dmnsn_scene *scene,
 /* Shoot a ray, and calculate the color, using `color' as the background */
 static dmnsn_color
 dmnsn_raytrace_shoot(dmnsn_line ray, dmnsn_scene *scene,
-                     dmnsn_kD_splay_tree *kD_splay_tree, dmnsn_color color)
+                     dmnsn_kD_splay_tree *kD_splay_tree, dmnsn_color background)
 {
   dmnsn_intersection *intersection = dmnsn_kD_splay_search(kD_splay_tree, ray);
 
+  dmnsn_color color = background;
   if (intersection) {
-    /* Default to black if we aren't rendering pigments */
-    color = dmnsn_black;
-
+    /* Get the pigment of the object */
+    dmnsn_color pigment = dmnsn_black;
     if (scene->quality >= DMNSN_RENDER_PIGMENT) {
-      color = dmnsn_raytrace_pigment(intersection, scene);
+      pigment = dmnsn_raytrace_pigment(intersection, scene);
     }
+    color = pigment;
+    color.filter = 0.0;
+    color.trans  = 0.0;
 
+    /* Account for finishes and shadows */
+    dmnsn_color illum = pigment;
     if (scene->quality >= DMNSN_RENDER_LIGHTS) {
-      color = dmnsn_raytrace_lighting(intersection,
+      illum = dmnsn_raytrace_lighting(intersection,
                                       scene,
                                       kD_splay_tree,
-                                      color);
+                                      pigment);
+    }
+    color = illum;
+    color.filter = 0.0;
+    color.trans  = 0.0;
+
+    /* Account for translucency */
+    dmnsn_color trans = illum;
+    if (scene->quality >= DMNSN_RENDER_TRANSLUCENCY
+        && (pigment.filter || pigment.trans))
+    {
+      trans = dmnsn_color_mul(1.0 - pigment.filter - pigment.trans, illum);
+      trans.filter = 0.0;
+      trans.trans  = 0.0;
+
+      dmnsn_line trans_ray = dmnsn_line_construct(
+        dmnsn_vector_add(
+          dmnsn_line_point(ray, intersection->t),
+          dmnsn_vector_mul(1.0e-9, ray.n)
+        ),
+        ray.n
+      );
+      trans_ray.n  = ray.n;
+
+      dmnsn_color rec = dmnsn_raytrace_shoot(trans_ray,
+                                             scene,
+                                             kD_splay_tree,
+                                             background);
+      dmnsn_color filtered = dmnsn_color_filter(rec, pigment);
+      trans = dmnsn_color_add(trans, filtered);
     }
+    color = trans;
 
     dmnsn_delete_intersection(intersection);
   }