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diff --git a/libdimension/model/objects/csg.c b/libdimension/model/objects/csg.c
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+/*************************************************************************
+ * 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
+ * Constructive solid geometry.
+ */
+
+#include "internal.h"
+#include "internal/bvh.h"
+#include "dimension/model.h"
+#include <stdlib.h>
+
+////////////
+// Unions //
+////////////
+
+typedef struct {
+ dmnsn_object object;
+ dmnsn_bvh *bvh;
+} dmnsn_csg_union;
+
+/// CSG union intersection callback.
+static bool
+dmnsn_csg_union_intersection_fn(const dmnsn_object *object,
+ dmnsn_ray ray,
+ dmnsn_intersection *intersection)
+{
+ const dmnsn_csg_union *csg = (const dmnsn_csg_union *)object;
+ return dmnsn_bvh_intersection(csg->bvh, ray, intersection, true);
+}
+
+/// CSG union inside callback.
+static bool
+dmnsn_csg_union_inside_fn(const dmnsn_object *object, dmnsn_vector point)
+{
+ const dmnsn_csg_union *csg = (const dmnsn_csg_union *)object;
+ return dmnsn_bvh_inside(csg->bvh, point);
+}
+
+/// CSG union precomputation callback.
+static void
+dmnsn_csg_union_precompute_fn(dmnsn_object *object)
+{
+ dmnsn_csg_union *csg = (dmnsn_csg_union *)object;
+ csg->object.trans_inv = dmnsn_identity_matrix();
+
+ dmnsn_bvh *bvh = dmnsn_new_bvh(csg->object.children, DMNSN_BVH_PRTREE);
+ csg->bvh = bvh;
+ csg->object.aabb = dmnsn_bvh_aabb(bvh);
+}
+
+/// CSG union vtable.
+static const dmnsn_object_vtable dmnsn_csg_union_vtable = {
+ .intersection_fn = dmnsn_csg_union_intersection_fn,
+ .inside_fn = dmnsn_csg_union_inside_fn,
+ .precompute_fn = dmnsn_csg_union_precompute_fn,
+};
+
+/// CSG union destruction callback.
+static void
+dmnsn_csg_union_cleanup(void *ptr)
+{
+ dmnsn_csg_union *csg = ptr;
+ dmnsn_delete_bvh(csg->bvh);
+}
+
+// Bulk-load a union
+dmnsn_object *
+dmnsn_new_csg_union(dmnsn_pool *pool, dmnsn_array *objects)
+{
+ dmnsn_csg_union *csg = DMNSN_PALLOC_TIDY(pool, dmnsn_csg_union, dmnsn_csg_union_cleanup);
+ csg->bvh = NULL;
+
+ dmnsn_object *object = &csg->object;
+ dmnsn_init_object(object);
+
+ object->vtable = &dmnsn_csg_union_vtable;
+ object->children = objects;
+ object->split_children = true;
+
+ return object;
+}
+
+/**
+ * Generic CSG intersection callback.
+ * @param[in] csg The CSG object.
+ * @param[in] ray The intersection ray.
+ * @param[out] intersection The intersection data.
+ * @param[in] inside1 Whether the first object is allowed inside the
+ * second object.
+ * @param[in] inside2 Whether the second object is allowed inside the
+ * first object.
+ * @return Whether \p ray intersected \p csg.
+ */
+static bool
+dmnsn_csg_intersection_fn(const dmnsn_object *csg, dmnsn_ray ray,
+ dmnsn_intersection *intersection,
+ bool inside1, bool inside2)
+{
+ const dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
+ const dmnsn_object *B = *(dmnsn_object **)dmnsn_array_last(csg->children);
+
+ dmnsn_intersection i1, i2;
+ bool is_i1 = dmnsn_object_intersection(A, ray, &i1);
+ bool is_i2 = dmnsn_object_intersection(B, ray, &i2);
+
+ double oldt = 0.0;
+ while (is_i1) {
+ i1.ray = ray;
+ i1.t += oldt;
+ oldt = i1.t + dmnsn_epsilon;
+
+ dmnsn_vector point = dmnsn_ray_point(i1.ray, i1.t);
+ if (inside2 ^ dmnsn_object_inside(B, point)) {
+ dmnsn_ray newray = ray;
+ newray.x0 = dmnsn_ray_point(ray, i1.t);
+ newray = dmnsn_ray_add_epsilon(newray);
+ is_i1 = dmnsn_object_intersection(A, newray, &i1);
+ } else {
+ break;
+ }
+ }
+
+ oldt = 0.0;
+ while (is_i2) {
+ i2.ray = ray;
+ i2.t += oldt;
+ oldt = i2.t + dmnsn_epsilon;
+
+ dmnsn_vector point = dmnsn_ray_point(i2.ray, i2.t);
+ if (inside1 ^ dmnsn_object_inside(A, point)) {
+ dmnsn_ray newray = ray;
+ newray.x0 = dmnsn_ray_point(ray, i2.t);
+ newray = dmnsn_ray_add_epsilon(newray);
+ is_i2 = dmnsn_object_intersection(B, newray, &i2);
+ } else {
+ break;
+ }
+ }
+
+ if (is_i1 && is_i2) {
+ if (i1.t < i2.t) {
+ *intersection = i1;
+ } else {
+ *intersection = i2;
+ }
+ } else if (is_i1) {
+ *intersection = i1;
+ } else if (is_i2) {
+ *intersection = i2;
+ } else {
+ return false;
+ }
+
+ return true;
+}
+
+///////////////////
+// Intersections //
+///////////////////
+
+/// CSG intersection intersection callback.
+static bool
+dmnsn_csg_intersection_intersection_fn(const dmnsn_object *csg,
+ dmnsn_ray ray,
+ dmnsn_intersection *intersection)
+{
+ return dmnsn_csg_intersection_fn(csg, ray, intersection, true, true);
+}
+
+/// CSG intersection inside callback.
+static bool
+dmnsn_csg_intersection_inside_fn(const dmnsn_object *csg, dmnsn_vector point)
+{
+ const dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
+ const dmnsn_object *B = *(dmnsn_object **)dmnsn_array_last(csg->children);
+ return dmnsn_object_inside(A, point) && dmnsn_object_inside(B, point);
+}
+
+/// CSG intersection precomputation callback.
+static void
+dmnsn_csg_intersection_precompute_fn(dmnsn_object *csg)
+{
+ dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
+ dmnsn_object *B = *(dmnsn_object **)dmnsn_array_last(csg->children);
+
+ csg->trans_inv = dmnsn_identity_matrix();
+ csg->aabb.min = dmnsn_vector_max(A->aabb.min, B->aabb.min);
+ csg->aabb.max = dmnsn_vector_min(A->aabb.max, B->aabb.max);
+}
+
+/// CSG intersection vtable.
+static const dmnsn_object_vtable dmnsn_csg_intersection_vtable = {
+ .intersection_fn = dmnsn_csg_intersection_intersection_fn,
+ .inside_fn = dmnsn_csg_intersection_inside_fn,
+ .precompute_fn = dmnsn_csg_intersection_precompute_fn,
+};
+
+dmnsn_object *
+dmnsn_new_csg_intersection(dmnsn_pool *pool, dmnsn_object *A, dmnsn_object *B)
+{
+ dmnsn_object *csg = dmnsn_new_object(pool);
+ csg->vtable = &dmnsn_csg_intersection_vtable;
+
+ csg->children = DMNSN_PALLOC_ARRAY(pool, dmnsn_object *);
+ dmnsn_array_push(csg->children, &A);
+ dmnsn_array_push(csg->children, &B);
+
+ return csg;
+}
+
+/////////////////
+// Differences //
+/////////////////
+
+/// CSG difference intersection callback.
+static bool
+dmnsn_csg_difference_intersection_fn(const dmnsn_object *csg,
+ dmnsn_ray ray,
+ dmnsn_intersection *intersection)
+{
+ return dmnsn_csg_intersection_fn(csg, ray, intersection, true, false);
+}
+
+/// CSG difference inside callback.
+static bool
+dmnsn_csg_difference_inside_fn(const dmnsn_object *csg, dmnsn_vector point)
+{
+ const dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
+ const dmnsn_object *B = *(dmnsn_object **)dmnsn_array_last(csg->children);
+ return dmnsn_object_inside(A, point) && !dmnsn_object_inside(B, point);
+}
+
+/// CSG difference precomputation callback.
+static void
+dmnsn_csg_difference_precompute_fn(dmnsn_object *csg)
+{
+ dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
+
+ csg->trans_inv = dmnsn_identity_matrix();
+ csg->aabb = A->aabb;
+}
+
+/// CSG difference vtable.
+static const dmnsn_object_vtable dmnsn_csg_difference_vtable = {
+ .intersection_fn = dmnsn_csg_difference_intersection_fn,
+ .inside_fn = dmnsn_csg_difference_inside_fn,
+ .precompute_fn = dmnsn_csg_difference_precompute_fn,
+};
+
+dmnsn_object *
+dmnsn_new_csg_difference(dmnsn_pool *pool, dmnsn_object *A, dmnsn_object *B)
+{
+ dmnsn_object *csg = dmnsn_new_object(pool);
+ csg->vtable = &dmnsn_csg_difference_vtable;
+
+ csg->children = DMNSN_PALLOC_ARRAY(pool, dmnsn_object *);
+ dmnsn_array_push(csg->children, &A);
+ dmnsn_array_push(csg->children, &B);
+
+ return csg;
+}
+
+////////////
+// Merges //
+////////////
+
+/// CSG merge intersection callback.
+static bool
+dmnsn_csg_merge_intersection_fn(const dmnsn_object *csg,
+ dmnsn_ray ray,
+ dmnsn_intersection *intersection)
+{
+ return dmnsn_csg_intersection_fn(csg, ray, intersection, false, false);
+}
+
+/// CSG merge inside callback.
+static bool
+dmnsn_csg_merge_inside_fn(const dmnsn_object *csg, dmnsn_vector point)
+{
+ const dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
+ const dmnsn_object *B = *(dmnsn_object **)dmnsn_array_last(csg->children);
+ return dmnsn_object_inside(A, point) || dmnsn_object_inside(B, point);
+}
+
+/// CSG merge precomputation callback.
+static void
+dmnsn_csg_merge_precompute_fn(dmnsn_object *csg)
+{
+ dmnsn_object *A = *(dmnsn_object **)dmnsn_array_first(csg->children);
+ dmnsn_object *B = *(dmnsn_object **)dmnsn_array_last(csg->children);
+
+ csg->trans_inv = dmnsn_identity_matrix();
+ csg->aabb.min = dmnsn_vector_min(A->aabb.min, B->aabb.min);
+ csg->aabb.max = dmnsn_vector_max(A->aabb.max, B->aabb.max);
+}
+
+/// CSG merge vtable.
+static const dmnsn_object_vtable dmnsn_csg_merge_vtable = {
+ .intersection_fn = dmnsn_csg_merge_intersection_fn,
+ .inside_fn = dmnsn_csg_merge_inside_fn,
+ .precompute_fn = dmnsn_csg_merge_precompute_fn,
+};
+
+dmnsn_object *
+dmnsn_new_csg_merge(dmnsn_pool *pool, dmnsn_object *A, dmnsn_object *B)
+{
+ dmnsn_object *csg = dmnsn_new_object(pool);
+ csg->vtable = &dmnsn_csg_merge_vtable;
+
+ csg->children = DMNSN_PALLOC_ARRAY(pool, dmnsn_object *);
+ dmnsn_array_push(csg->children, &A);
+ dmnsn_array_push(csg->children, &B);
+
+ return csg;
+}
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