Modularize the libdimension codebase.

1 files changed, 347 insertions, 0 deletions

diff --git a/libdimension/model/objects/triangle_fan.c b/libdimension/model/objects/triangle_fan.c
new file mode 100644
index 0000000..93768a9
--- /dev/null
+++ b/libdimension/model/objects/triangle_fan.c
@@ -0,0 +1,347 @@
+/*************************************************************************
+ * Copyright (C) 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
+ * Triangle fans.  See
+ * http://tavianator.com/2014/05/a-beautiful-raymesh-intersection-algorithm/
+ * for a description of the intersection algorithm.
+ */
+
+#include "internal.h"
+#include "dimension/model.h"
+
+/// Triangle fan type.
+typedef struct {
+  dmnsn_object object;
+  size_t ncoeffs;
+  double coeffs[][6];
+} dmnsn_triangle_fan;
+
+/// Change basis from one triangle to the next.
+static inline dmnsn_vector
+dmnsn_change_basis(const double coeffs[6], dmnsn_vector v)
+{
+  return dmnsn_new_vector(
+    coeffs[0]*v.x + coeffs[1]*v.z + v.y,
+    coeffs[2]*v.x + coeffs[3]*v.z,
+    coeffs[4]*v.x + coeffs[5]*v.z
+  );
+}
+
+/// Change basis from one triangle to the next for a normal vector.
+static inline dmnsn_vector
+dmnsn_change_normal_basis(const double coeffs[6], dmnsn_vector n)
+{
+  return dmnsn_new_vector(
+    coeffs[0]*n.x + coeffs[2]*n.y + coeffs[4]*n.z,
+    n.x,
+    coeffs[1]*n.x + coeffs[3]*n.y + coeffs[5]*n.z
+  );
+}
+
+/// Change basis from one triangle to the next for a ray
+static inline dmnsn_ray
+dmnsn_change_ray_basis(const double coeffs[6], dmnsn_ray l)
+{
+  return dmnsn_new_ray(dmnsn_change_basis(coeffs, l.x0), dmnsn_change_basis(coeffs, l.n));
+}
+
+/// Store the compressed incremental matrix.
+static inline void
+dmnsn_compress_coeffs(double coeffs[6], dmnsn_matrix incremental)
+{
+  coeffs[0] = incremental.n[0][0];
+  coeffs[1] = incremental.n[0][2];
+  coeffs[2] = incremental.n[1][0];
+  coeffs[3] = incremental.n[1][2];
+  coeffs[4] = incremental.n[2][0];
+  coeffs[5] = incremental.n[2][2];
+}
+
+/// Decompress the incremental matrix.
+static inline dmnsn_matrix
+dmnsn_decompress_coeffs(const double coeffs[6])
+{
+  dmnsn_matrix incremental = dmnsn_new_matrix(
+    coeffs[0], 1.0, coeffs[1], 0.0,
+    coeffs[2], 0.0, coeffs[3], 0.0,
+    coeffs[4], 0.0, coeffs[5], 0.0
+  );
+  return incremental;
+}
+
+/// Make a change-of-basis matrix for a triangle.
+static inline dmnsn_matrix
+dmnsn_triangle_basis(dmnsn_vector a, dmnsn_vector ab, dmnsn_vector ac)
+{
+  dmnsn_vector normal = dmnsn_vector_cross(ab, ac);
+  return dmnsn_new_matrix4(ab, ac, normal, a);
+}
+
+/// Optimized ray/triangle intersection test.
+static inline bool
+dmnsn_ray_triangle_intersection(dmnsn_ray l, double *t, double *u, double *v)
+{
+  *t = -l.x0.z/l.n.z;
+  *u = l.x0.x + (*t)*l.n.x;
+  *v = l.x0.y + (*t)*l.n.y;
+  return *t >= 0.0 && *u >= 0.0 && *v >= 0.0 && *u + *v <= 1.0;
+}
+
+/// Triangle fan intersection callback.
+DMNSN_HOT static bool
+dmnsn_triangle_fan_intersection_fn(const dmnsn_object *object, dmnsn_ray l, dmnsn_intersection *intersection)
+{
+  const dmnsn_triangle_fan *fan = (const dmnsn_triangle_fan *)object;
+
+  double t, u, v;
+
+  double best_t = INFINITY;
+  if (dmnsn_ray_triangle_intersection(l, &t, &u, &v)) {
+    best_t = t;
+  }
+
+  dmnsn_vector normal = dmnsn_z;
+  dmnsn_vector best_normal = normal;
+
+  for (size_t i = 0; i < fan->ncoeffs; ++i) {
+    const double *coeffs = fan->coeffs[i];
+    l = dmnsn_change_ray_basis(coeffs, l);
+    normal = dmnsn_change_normal_basis(coeffs, normal);
+
+    if (dmnsn_ray_triangle_intersection(l, &t, &u, &v) && t < best_t) {
+      best_t = t;
+      best_normal = normal;
+    }
+  }
+
+  if (!isinf(best_t)) {
+    intersection->t = t;
+    intersection->normal = best_normal;
+    return true;
+  }
+
+  return false;
+}
+
+/// Triangle fan inside callback.
+static bool
+dmnsn_triangle_fan_inside_fn(const dmnsn_object *object, dmnsn_vector point)
+{
+  return false;
+}
+
+/// Computes the bounding box for the first triangle
+static inline dmnsn_aabb
+dmnsn_bound_first_triangle(dmnsn_matrix trans)
+{
+  dmnsn_vector a = dmnsn_transform_point(trans, dmnsn_zero);
+  dmnsn_vector b = dmnsn_transform_point(trans, dmnsn_x);
+  dmnsn_vector c = dmnsn_transform_point(trans, dmnsn_y);
+
+  dmnsn_aabb box = dmnsn_new_aabb(a, a);
+  box = dmnsn_aabb_swallow(box, b);
+  box = dmnsn_aabb_swallow(box, c);
+
+  return box;
+}
+
+/// Triangle fan bounding callback.
+static dmnsn_aabb
+dmnsn_triangle_fan_bounding_fn(const dmnsn_object *object, dmnsn_matrix trans)
+{
+  const dmnsn_triangle_fan *fan = (const dmnsn_triangle_fan *)object;
+
+  dmnsn_aabb box = dmnsn_bound_first_triangle(trans);
+
+  for (size_t i = 0; i < fan->ncoeffs; ++i) {
+    dmnsn_matrix incremental = dmnsn_decompress_coeffs(fan->coeffs[i]);
+    trans = dmnsn_matrix_mul(trans, dmnsn_matrix_inverse(incremental));
+    dmnsn_vector vertex = dmnsn_transform_point(trans, dmnsn_y);
+    box = dmnsn_aabb_swallow(box, vertex);
+  }
+
+  return box;
+}
+
+/// Triangle fan vtable.
+static dmnsn_object_vtable dmnsn_triangle_fan_vtable = {
+  .intersection_fn = dmnsn_triangle_fan_intersection_fn,
+  .inside_fn = dmnsn_triangle_fan_inside_fn,
+  .bounding_fn = dmnsn_triangle_fan_bounding_fn,
+};
+
+/// Smooth triangle fan type.
+typedef struct dmnsn_smooth_triangle_fan {
+  dmnsn_object object;
+  dmnsn_vector na, nab, nac;
+  size_t ncoeffs;
+  double coeffs[][9]; ///< 0-6 is same as dmnsn_triangle_fan, 6-9 is the normal
+} dmnsn_smooth_triangle_fan;
+
+/// Smooth triangle fan intersection callback.
+DMNSN_HOT static bool
+dmnsn_smooth_triangle_fan_intersection_fn(const dmnsn_object *object, dmnsn_ray l, dmnsn_intersection *intersection)
+{
+  const dmnsn_smooth_triangle_fan *fan = (const dmnsn_smooth_triangle_fan *)object;
+
+  dmnsn_vector nab = fan->nab;
+  dmnsn_vector nac = fan->nac;
+
+  double t, u, v;
+
+  double best_t = INFINITY;
+  dmnsn_vector best_normal;
+  if (dmnsn_ray_triangle_intersection(l, &t, &u, &v)) {
+    best_t = t;
+    best_normal = dmnsn_vector_add(dmnsn_vector_mul(u, nab), dmnsn_vector_mul(v, nac));
+  }
+
+  for (size_t i = 0; i < fan->ncoeffs; ++i) {
+    const double *coeffs = fan->coeffs[i];
+    l = dmnsn_change_ray_basis(coeffs, l);
+    nab = nac;
+    nac = dmnsn_new_vector(coeffs[6], coeffs[7], coeffs[8]);
+
+    if (dmnsn_ray_triangle_intersection(l, &t, &u, &v) && t < best_t) {
+      best_t = t;
+      best_normal = dmnsn_vector_add(dmnsn_vector_mul(u, nab), dmnsn_vector_mul(v, nac));
+    }
+  }
+
+  if (!isinf(best_t)) {
+    intersection->t = t;
+    intersection->normal = dmnsn_vector_add(fan->na, best_normal);
+    return true;
+  }
+
+  return false;
+}
+
+/// Smooth triangle fan bounding callback.
+static dmnsn_aabb
+dmnsn_smooth_triangle_fan_bounding_fn(const dmnsn_object *object, dmnsn_matrix trans)
+{
+  const dmnsn_smooth_triangle_fan *fan = (const dmnsn_smooth_triangle_fan *)object;
+
+  dmnsn_aabb box = dmnsn_bound_first_triangle(trans);
+
+  for (size_t i = 0; i < fan->ncoeffs; ++i) {
+    dmnsn_matrix incremental = dmnsn_decompress_coeffs(fan->coeffs[i]);
+    trans = dmnsn_matrix_mul(trans, dmnsn_matrix_inverse(incremental));
+    dmnsn_vector vertex = dmnsn_transform_point(trans, dmnsn_y);
+    box = dmnsn_aabb_swallow(box, vertex);
+  }
+
+  return box;
+}
+
+/// Smooth triangle fan vtable.
+static dmnsn_object_vtable dmnsn_smooth_triangle_fan_vtable = {
+  .intersection_fn = dmnsn_smooth_triangle_fan_intersection_fn,
+  .inside_fn = dmnsn_triangle_fan_inside_fn,
+  .bounding_fn = dmnsn_smooth_triangle_fan_bounding_fn,
+};
+
+dmnsn_object *
+dmnsn_new_triangle_fan(dmnsn_pool *pool, dmnsn_vector vertices[], size_t nvertices)
+{
+  dmnsn_assert(nvertices >= 3, "Not enough vertices for one triangle");
+
+  size_t ncoeffs = nvertices - 3;
+  dmnsn_triangle_fan *fan = dmnsn_palloc(pool, sizeof(dmnsn_triangle_fan) + ncoeffs*sizeof(double[6]));
+  fan->ncoeffs = ncoeffs;
+
+  dmnsn_object *object = &fan->object;
+  dmnsn_init_object(object);
+  object->vtable = &dmnsn_triangle_fan_vtable;
+
+  // Compute the initial matrix and the coefficients
+  dmnsn_vector a = vertices[0];
+  dmnsn_vector ab = dmnsn_vector_sub(vertices[1], a);
+  dmnsn_vector ac = dmnsn_vector_sub(vertices[2], a);
+  dmnsn_matrix P = dmnsn_triangle_basis(a, ab, ac);
+  object->intrinsic_trans = P;
+
+  for (size_t i = 0; i < ncoeffs; ++i) {
+    ab = ac;
+    ac = dmnsn_vector_sub(vertices[i + 3], a);
+
+    dmnsn_matrix newP = dmnsn_triangle_basis(a, ab, ac);
+    dmnsn_matrix incremental = dmnsn_matrix_mul(dmnsn_matrix_inverse(newP), P);
+    dmnsn_compress_coeffs(fan->coeffs[i], incremental);
+
+    P = newP;
+  }
+
+  return object;
+}
+
+dmnsn_object *
+dmnsn_new_smooth_triangle_fan(dmnsn_pool *pool, dmnsn_vector vertices[], dmnsn_vector normals[], size_t nvertices)
+{
+  dmnsn_assert(nvertices >= 3, "Not enough vertices for one triangle");
+
+  size_t ncoeffs = nvertices - 3;
+  dmnsn_smooth_triangle_fan *fan = dmnsn_palloc(pool, sizeof(dmnsn_smooth_triangle_fan) + ncoeffs*sizeof(double[9]));
+  fan->ncoeffs = ncoeffs;
+
+  dmnsn_object *object = &fan->object;
+  dmnsn_init_object(object);
+  object->vtable = &dmnsn_smooth_triangle_fan_vtable;
+
+  // Compute the initial matrix
+  dmnsn_vector a = vertices[0];
+  dmnsn_vector ab = dmnsn_vector_sub(vertices[1], a);
+  dmnsn_vector ac = dmnsn_vector_sub(vertices[2], a);
+  dmnsn_matrix P = dmnsn_triangle_basis(a, ab, ac);
+  dmnsn_matrix Pabc = P;
+  object->intrinsic_trans = P;
+
+  // Transform the first three normals
+  dmnsn_vector na = dmnsn_vector_normalized(dmnsn_transform_normal(P, normals[0]));
+  dmnsn_vector nb = dmnsn_vector_normalized(dmnsn_transform_normal(P, normals[1]));
+  dmnsn_vector nc = dmnsn_vector_normalized(dmnsn_transform_normal(P, normals[2]));
+  fan->na = na;
+  fan->nab = dmnsn_vector_sub(nb, na);
+  fan->nac = dmnsn_vector_sub(nc, na);
+
+  // Compute the coefficients
+  for (size_t i = 0; i < ncoeffs; ++i) {
+    ab = ac;
+    ac = dmnsn_vector_sub(vertices[i + 3], a);
+
+    dmnsn_matrix newP = dmnsn_triangle_basis(a, ab, ac);
+    dmnsn_matrix incremental = dmnsn_matrix_mul(dmnsn_matrix_inverse(newP), P);
+    double *coeffs = fan->coeffs[i];
+    dmnsn_compress_coeffs(coeffs, incremental);
+
+    nc = dmnsn_vector_normalized(dmnsn_transform_normal(Pabc, normals[i + 3]));
+    dmnsn_vector nac = dmnsn_vector_sub(nc, na);
+    coeffs[6] = nac.x;
+    coeffs[7] = nac.y;
+    coeffs[8] = nac.z;
+
+    P = newP;
+  }
+
+  return object;
+}