Modularize the libdimension codebase.

1 files changed, 548 insertions, 0 deletions

diff --git a/libdimension/render/render.c b/libdimension/render/render.c
new file mode 100644
index 0000000..842b41e
--- /dev/null
+++ b/libdimension/render/render.c
@@ -0,0 +1,548 @@
+/*************************************************************************
+ * Copyright (C) 2010-2014 Tavian Barnes <tavianator@tavianator.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
+ * The ray-tracing algorithm.
+ */
+
+#include "internal/bvh.h"
+#include "internal/concurrency.h"
+#include "dimension/render.h"
+#include <stdlib.h>
+
+////////////////////////////////////
+// Boilerplate for multithreading //
+////////////////////////////////////
+
+/// Payload type for passing arguments to worker threads.
+typedef struct {
+  dmnsn_future *future;
+  dmnsn_scene *scene;
+  dmnsn_bvh *bvh;
+} dmnsn_render_payload;
+
+// Ray-trace a scene
+void
+dmnsn_render(dmnsn_scene *scene)
+{
+  dmnsn_future *future = dmnsn_render_async(scene);
+  if (dmnsn_future_join(future) != 0) {
+    dmnsn_error("Error occured while ray-tracing.");
+  }
+}
+
+/// Background thread callback.
+static int dmnsn_render_scene_thread(void *ptr);
+
+// Ray-trace a scene in the background
+dmnsn_future *
+dmnsn_render_async(dmnsn_scene *scene)
+{
+  dmnsn_future *future = dmnsn_new_future();
+
+  dmnsn_render_payload *payload = DMNSN_MALLOC(dmnsn_render_payload);
+  payload->future = future;
+  payload->scene  = scene;
+
+  dmnsn_new_thread(future, dmnsn_render_scene_thread, payload);
+
+  return future;
+}
+
+/// Worker thread callback.
+static int dmnsn_render_scene_concurrent(void *ptr, unsigned int thread,
+                                            unsigned int nthreads);
+
+// Thread callback -- set up the multithreaded engine
+static int
+dmnsn_render_scene_thread(void *ptr)
+{
+  dmnsn_render_payload *payload = ptr;
+
+  // Pre-calculate bounding box transformations, etc.
+  dmnsn_scene_initialize(payload->scene);
+
+  // Time the bounding tree construction
+  dmnsn_timer_start(&payload->scene->bounding_timer);
+    payload->bvh = dmnsn_new_bvh(payload->scene->objects, DMNSN_BVH_PRTREE);
+  dmnsn_timer_stop(&payload->scene->bounding_timer);
+
+  // Set up the future object
+  dmnsn_future_set_total(payload->future, payload->scene->canvas->height);
+
+  // Time the render itself
+  dmnsn_timer_start(&payload->scene->render_timer);
+    int ret = dmnsn_execute_concurrently(payload->future,
+                                         dmnsn_render_scene_concurrent,
+                                         payload, payload->scene->nthreads);
+  dmnsn_timer_stop(&payload->scene->render_timer);
+
+  dmnsn_delete_bvh(payload->bvh);
+  dmnsn_free(payload);
+
+  return ret;
+}
+
+///////////////////////////
+// Ray-tracing algorithm //
+///////////////////////////
+
+/// The current state of the ray-tracing engine.
+typedef struct dmnsn_rtstate {
+  const struct dmnsn_rtstate *parent;
+
+  const dmnsn_scene *scene;
+  const dmnsn_intersection *intersection;
+  const dmnsn_texture *texture;
+  const dmnsn_interior *interior;
+  const dmnsn_bvh *bvh;
+  unsigned int reclevel;
+
+  dmnsn_vector r;
+  dmnsn_vector pigment_r;
+  dmnsn_vector viewer;
+  dmnsn_vector reflected;
+
+  bool is_shadow_ray;
+  dmnsn_vector light_ray;
+  dmnsn_color light_color;
+
+  dmnsn_tcolor pigment;
+  dmnsn_tcolor color;
+
+  double ior;
+
+  dmnsn_color adc_value;
+} dmnsn_rtstate;
+
+/// Compute a ray-tracing state from an intersection.
+static inline void
+dmnsn_rtstate_initialize(dmnsn_rtstate *state,
+                         const dmnsn_intersection *intersection);
+/// Main helper for dmnsn_render_scene_concurrent - shoot a ray.
+static dmnsn_tcolor dmnsn_ray_shoot(dmnsn_rtstate *state, dmnsn_ray ray);
+
+// Actually ray-trace a scene
+static int
+dmnsn_render_scene_concurrent(void *ptr, unsigned int thread, unsigned int nthreads)
+{
+  const dmnsn_render_payload *payload = ptr;
+  dmnsn_future *future = payload->future;
+  dmnsn_scene *scene = payload->scene;
+  dmnsn_bvh *bvh = payload->bvh;
+
+  dmnsn_rtstate state = {
+    .parent = NULL,
+    .scene  = scene,
+    .bvh = bvh,
+  };
+
+  // Iterate through each pixel
+  for (size_t y = thread; y < scene->canvas->height; y += nthreads) {
+    for (size_t x = 0; x < scene->canvas->width; ++x) {
+      // Get the ray corresponding to the (x,y)'th pixel
+      dmnsn_ray ray = dmnsn_camera_ray(
+        scene->camera,
+        ((double)(x + scene->region_x))/(scene->outer_width - 1),
+        ((double)(y + scene->region_y))/(scene->outer_height - 1)
+      );
+
+      // Shoot a ray
+      state.reclevel = scene->reclimit;
+      state.ior = 1.0;
+      state.adc_value = dmnsn_white;
+      dmnsn_tcolor tcolor = dmnsn_ray_shoot(&state, ray);
+      dmnsn_canvas_set_pixel(scene->canvas, x, y, tcolor);
+    }
+
+    dmnsn_future_increment(future);
+  }
+
+  return 0;
+}
+
+// Compute rtstate fields
+static inline void
+dmnsn_rtstate_initialize(dmnsn_rtstate *state,
+                         const dmnsn_intersection *intersection)
+{
+  state->intersection = intersection;
+  state->texture      = intersection->object->texture;
+  state->interior     = intersection->object->interior;
+
+  state->r = dmnsn_ray_point(intersection->ray, intersection->t);
+  state->pigment_r = dmnsn_transform_point(
+    intersection->object->pigment_trans,
+    state->r
+  );
+  state->viewer = dmnsn_vector_normalized(
+    dmnsn_vector_negate(intersection->ray.n)
+  );
+  state->reflected = dmnsn_vector_sub(
+    dmnsn_vector_mul(
+      2*dmnsn_vector_dot(state->viewer, intersection->normal),
+      intersection->normal),
+    state->viewer
+  );
+
+  state->is_shadow_ray = false;
+}
+
+/// Calculate the background color.
+static void dmnsn_trace_background(dmnsn_rtstate *state, dmnsn_ray ray);
+/// Calculate the base pigment at the intersection.
+static void dmnsn_trace_pigment(dmnsn_rtstate *state);
+/// Handle light, shadow, and shading.
+static void dmnsn_trace_lighting(dmnsn_rtstate *state);
+/// Trace a reflected ray.
+static void dmnsn_trace_reflection(dmnsn_rtstate *state);
+/// Trace a transmitted ray.
+static void dmnsn_trace_transparency(dmnsn_rtstate *state);
+
+// Shoot a ray, and calculate the color
+static dmnsn_tcolor
+dmnsn_ray_shoot(dmnsn_rtstate *state, dmnsn_ray ray)
+{
+  if (state->reclevel == 0
+      || dmnsn_color_intensity(state->adc_value) < state->scene->adc_bailout)
+  {
+    return DMNSN_TCOLOR(dmnsn_black);
+  }
+
+  --state->reclevel;
+
+  dmnsn_intersection intersection;
+  bool reset = state->reclevel == state->scene->reclimit - 1;
+  dmnsn_bvh_intersection(state->bvh, ray, &intersection, reset);
+  if (dmnsn_bvh_intersection(state->bvh, ray, &intersection, reset)) {
+    // Found an intersection
+    dmnsn_rtstate_initialize(state, &intersection);
+
+    dmnsn_trace_pigment(state);
+    if (state->scene->quality & DMNSN_RENDER_LIGHTS) {
+      dmnsn_trace_lighting(state);
+    }
+    if (state->scene->quality & DMNSN_RENDER_REFLECTION) {
+      dmnsn_trace_reflection(state);
+    }
+    if (state->scene->quality & DMNSN_RENDER_TRANSPARENCY) {
+      dmnsn_trace_transparency(state);
+    }
+  } else {
+    // No intersection, return the background color
+    dmnsn_trace_background(state, ray);
+  }
+
+  return state->color;
+}
+
+static void
+dmnsn_trace_background(dmnsn_rtstate *state, dmnsn_ray ray)
+{
+  dmnsn_pigment *background = state->scene->background;
+  if (state->scene->quality & DMNSN_RENDER_PIGMENT) {
+    dmnsn_vector r = dmnsn_vector_normalized(ray.n);
+    state->color = dmnsn_pigment_evaluate(background, r);
+  } else {
+    state->color = background->quick_color;
+  }
+}
+
+static void
+dmnsn_trace_pigment(dmnsn_rtstate *state)
+{
+  dmnsn_pigment *pigment = state->texture->pigment;
+  if (state->scene->quality & DMNSN_RENDER_PIGMENT) {
+    state->pigment = dmnsn_pigment_evaluate(pigment, state->pigment_r);
+  } else {
+    state->pigment = pigment->quick_color;
+  }
+  state->color = state->pigment;
+}
+
+/// Determine the amount of specular highlight.
+static inline dmnsn_color
+dmnsn_evaluate_specular(const dmnsn_rtstate *state)
+{
+  const dmnsn_finish *finish = &state->texture->finish;
+  if (finish->specular) {
+    return finish->specular->specular_fn(
+      finish->specular, state->light_color, state->pigment.c,
+      state->light_ray, state->intersection->normal, state->viewer
+    );
+  } else {
+    return dmnsn_black;
+  }
+}
+
+/// Determine the amount of reflected light.
+static inline dmnsn_color
+dmnsn_evaluate_reflection(const dmnsn_rtstate *state,
+                          dmnsn_color light, dmnsn_vector direction)
+{
+  const dmnsn_reflection *reflection = state->texture->finish.reflection;
+  if (reflection && (state->scene->quality & DMNSN_RENDER_REFLECTION)) {
+    return reflection->reflection_fn(
+      reflection, light, state->pigment.c, direction,
+      state->intersection->normal
+    );
+  } else {
+    return dmnsn_black;
+  }
+}
+
+/// Determine the amount of transmitted light.
+static inline dmnsn_color
+dmnsn_evaluate_transparency(const dmnsn_rtstate *state, dmnsn_color light)
+{
+  if (state->pigment.T >= dmnsn_epsilon
+      && (state->scene->quality & DMNSN_RENDER_TRANSPARENCY))
+  {
+    return dmnsn_tcolor_filter(light, state->pigment);
+  } else {
+    return dmnsn_black;
+  }
+}
+
+/// Get a light's diffuse contribution to the object
+static inline dmnsn_color
+dmnsn_evaluate_diffuse(const dmnsn_rtstate *state)
+{
+  const dmnsn_finish *finish = &state->texture->finish;
+  if (finish->diffuse) {
+    return finish->diffuse->diffuse_fn(
+      finish->diffuse, state->light_color, state->pigment.c,
+      state->light_ray, state->intersection->normal
+    );
+  } else {
+    return dmnsn_black;
+  }
+}
+
+/// Get the color of a light ray at an intersection point.
+static bool
+dmnsn_trace_light_ray(dmnsn_rtstate *state, const dmnsn_light *light)
+{
+  dmnsn_ray shadow_ray = dmnsn_new_ray(
+    state->r,
+    light->direction_fn(light, state->r)
+  );
+  // Add epsilon to avoid hitting ourselves with the shadow ray
+  shadow_ray = dmnsn_ray_add_epsilon(shadow_ray);
+
+  // Check if we're casting a shadow on ourself
+  if ((dmnsn_vector_dot(shadow_ray.n, state->intersection->normal)
+       * dmnsn_vector_dot(state->viewer, state->intersection->normal) < 0.0)
+      && (!state->is_shadow_ray || state->pigment.T < dmnsn_epsilon))
+  {
+    return false;
+  }
+
+  state->light_ray = dmnsn_vector_normalized(shadow_ray.n);
+  state->light_color = light->illumination_fn(light, state->r);
+
+  // Test for shadow ray intersections
+  dmnsn_intersection shadow_caster;
+  bool in_shadow = dmnsn_bvh_intersection(state->bvh, shadow_ray,
+                                          &shadow_caster, false);
+  if (!in_shadow || !light->shadow_fn(light, shadow_caster.t)) {
+    return true;
+  }
+
+  if (state->reclevel > 0
+      && dmnsn_color_intensity(state->adc_value) >= state->scene->adc_bailout
+      && (state->scene->quality & DMNSN_RENDER_TRANSPARENCY)) {
+    dmnsn_rtstate shadow_state = *state;
+    dmnsn_rtstate_initialize(&shadow_state, &shadow_caster);
+    dmnsn_trace_pigment(&shadow_state);
+
+    if (shadow_state.pigment.T >= dmnsn_epsilon) {
+      --shadow_state.reclevel;
+      shadow_state.adc_value = dmnsn_evaluate_transparency(
+        &shadow_state, shadow_state.adc_value
+      );
+      shadow_state.is_shadow_ray = true;
+      if (dmnsn_trace_light_ray(&shadow_state, light)) {
+        state->light_color = shadow_state.light_color;
+
+        // Handle reflection
+        dmnsn_color reflected = dmnsn_evaluate_reflection(
+          &shadow_state, state->light_color, state->light_ray
+        );
+        state->light_color = dmnsn_color_sub(state->light_color, reflected);
+
+        // Handle transparency
+        state->light_color = dmnsn_evaluate_transparency(
+          &shadow_state, state->light_color
+        );
+
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
+static void
+dmnsn_trace_lighting(dmnsn_rtstate *state)
+{
+  // Calculate the ambient color
+  state->color = DMNSN_TCOLOR(dmnsn_black);
+  const dmnsn_finish *finish = &state->texture->finish;
+  if (finish->ambient) {
+    dmnsn_color ambient = finish->ambient->ambient;
+
+    // Handle reflection and transmittance of the ambient light
+    dmnsn_color reflected = dmnsn_evaluate_reflection(
+      state, ambient, state->intersection->normal
+    );
+    ambient = dmnsn_color_sub(ambient, reflected);
+    dmnsn_color transmitted = dmnsn_evaluate_transparency(state, ambient);
+    ambient = dmnsn_color_sub(ambient, transmitted);
+
+    state->color.c = dmnsn_color_illuminate(ambient, state->pigment.c);
+  }
+
+  // Iterate over each light
+  DMNSN_ARRAY_FOREACH (dmnsn_light **, light, state->scene->lights) {
+    if (dmnsn_trace_light_ray(state, *light)) {
+      if (state->scene->quality & DMNSN_RENDER_FINISH) {
+        dmnsn_color specular = dmnsn_evaluate_specular(state);
+        state->light_color = dmnsn_color_sub(state->light_color, specular);
+
+        dmnsn_color reflected = dmnsn_evaluate_reflection(
+          state, state->light_color, state->reflected
+        );
+        state->light_color = dmnsn_color_sub(state->light_color, reflected);
+
+        dmnsn_color transmitted = dmnsn_evaluate_transparency(
+          state, state->light_color
+        );
+        state->light_color = dmnsn_color_sub(state->light_color, transmitted);
+
+        dmnsn_color diffuse = dmnsn_evaluate_diffuse(state);
+
+        state->color.c = dmnsn_color_add(state->color.c, specular);
+        state->color.c = dmnsn_color_add(state->color.c, diffuse);
+      } else {
+        state->color.c = state->pigment.c;
+        break;
+      }
+    }
+  }
+}
+
+static void
+dmnsn_trace_reflection(dmnsn_rtstate *state)
+{
+  const dmnsn_reflection *reflection = state->texture->finish.reflection;
+  if (reflection) {
+    dmnsn_ray refl_ray = dmnsn_new_ray(state->r, state->reflected);
+    refl_ray = dmnsn_ray_add_epsilon(refl_ray);
+
+    dmnsn_rtstate recursive_state = *state;
+
+    // Calculate ADC value
+    recursive_state.adc_value = dmnsn_evaluate_reflection(
+      state, state->adc_value, state->reflected
+    );
+
+    // Shoot the reflected ray
+    dmnsn_color rec = dmnsn_ray_shoot(&recursive_state, refl_ray).c;
+    dmnsn_color reflected = dmnsn_evaluate_reflection(
+      state, rec, state->reflected
+    );
+
+    state->color.c = dmnsn_color_add(state->color.c, reflected);
+  }
+}
+
+static void
+dmnsn_trace_transparency(dmnsn_rtstate *state)
+{
+  if (state->pigment.T >= dmnsn_epsilon) {
+    const dmnsn_interior *interior = state->interior;
+
+    dmnsn_ray trans_ray = dmnsn_new_ray(state->r, state->intersection->ray.n);
+    trans_ray = dmnsn_ray_add_epsilon(trans_ray);
+
+    dmnsn_vector r = dmnsn_vector_normalized(trans_ray.n);
+    dmnsn_vector n = state->intersection->normal;
+
+    dmnsn_rtstate recursive_state = *state;
+
+    // Calculate new refractive index
+    if (dmnsn_vector_dot(r, n) < 0.0) {
+      // We are entering an object
+      recursive_state.ior = interior->ior;
+      recursive_state.parent = state;
+    } else {
+      // We are leaving an object
+      recursive_state.ior = state->parent ? state->parent->ior : 1.0;
+      recursive_state.parent = state->parent ? state->parent->parent : NULL;
+    }
+
+    // Calculate transmitted ray direction
+    double iorr = state->ior/recursive_state.ior; // ior ratio
+    double c1 = -dmnsn_vector_dot(r, n);
+    double c2 = 1.0 - iorr*iorr*(1.0 - c1*c1);
+    if (c2 <= 0.0) {
+      // Total internal reflection
+      return;
+    }
+    c2 = sqrt(c2);
+    if (c1 >= 0.0) {
+      trans_ray.n = dmnsn_vector_add(
+        dmnsn_vector_mul(iorr, r),
+        dmnsn_vector_mul(iorr*c1 - c2, n)
+      );
+    } else {
+      trans_ray.n = dmnsn_vector_add(
+        dmnsn_vector_mul(iorr, r),
+        dmnsn_vector_mul(iorr*c1 + c2, n)
+      );
+    }
+
+    // Calculate ADC value
+    recursive_state.adc_value = dmnsn_evaluate_transparency(
+      state, state->adc_value
+    );
+    dmnsn_color adc_reflected = dmnsn_evaluate_reflection(
+      state, recursive_state.adc_value, state->reflected
+    );
+    recursive_state.adc_value = dmnsn_color_sub(
+      recursive_state.adc_value, adc_reflected
+    );
+
+    // Shoot the transmitted ray
+    dmnsn_color rec = dmnsn_ray_shoot(&recursive_state, trans_ray).c;
+    dmnsn_color filtered = dmnsn_evaluate_transparency(state, rec);
+
+    // Conserve energy
+    dmnsn_color reflected = dmnsn_evaluate_reflection(
+      state, filtered, state->reflected
+    );
+    filtered = dmnsn_color_sub(filtered, reflected);
+
+    state->color.c = dmnsn_color_add(state->color.c, filtered);
+  }
+}