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/*************************************************************************
* Copyright (C) 2009-2014 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
* Triangles. See
* http://tavianator.com/2014/05/a-beautiful-raytriangle-intersection-method/
* for a description of the intersection algorithm.
*/
#include "internal.h"
#include "dimension/model.h"
/// Optimized ray/triangle intersection test.
static inline bool
dmnsn_ray_triangle_intersection(dmnsn_ray l, double *t, double *u, double *v)
{
// See the change of basis in dmnsn_triangle_basis()
*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 intersection callback.
DMNSN_HOT static bool
dmnsn_triangle_intersection_fn(const dmnsn_object *object, dmnsn_ray l, dmnsn_intersection *intersection)
{
double t, u, v;
if (dmnsn_ray_triangle_intersection(l, &t, &u, &v)) {
intersection->t = t;
intersection->normal = dmnsn_z;
return true;
}
return false;
}
/// Triangle inside callback.
static bool
dmnsn_triangle_inside_fn(const dmnsn_object *object, dmnsn_vector point)
{
return false;
}
/// Triangle bounding callback.
static dmnsn_aabb
dmnsn_triangle_bounding_fn(const dmnsn_object *object, 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 vtable.
static const dmnsn_object_vtable dmnsn_triangle_vtable = {
.intersection_fn = dmnsn_triangle_intersection_fn,
.inside_fn = dmnsn_triangle_inside_fn,
.bounding_fn = dmnsn_triangle_bounding_fn,
};
/// Smooth triangle type.
typedef struct {
dmnsn_object object;
dmnsn_vector na, nab, nac;
} dmnsn_smooth_triangle;
/// Smooth triangle intersection callback.
DMNSN_HOT static bool
dmnsn_smooth_triangle_intersection_fn(const dmnsn_object *object, dmnsn_ray l,
dmnsn_intersection *intersection)
{
const dmnsn_smooth_triangle *triangle = (const dmnsn_smooth_triangle *)object;
double t, u, v;
if (dmnsn_ray_triangle_intersection(l, &t, &u, &v)) {
intersection->t = t;
intersection->normal = dmnsn_vector_add(
triangle->na,
dmnsn_vector_add(
dmnsn_vector_mul(u, triangle->nab),
dmnsn_vector_mul(v, triangle->nac)
)
);
return true;
}
return false;
}
/// Smooth triangle vtable.
static const dmnsn_object_vtable dmnsn_smooth_triangle_vtable = {
.intersection_fn = dmnsn_smooth_triangle_intersection_fn,
.inside_fn = dmnsn_triangle_inside_fn,
.bounding_fn = dmnsn_triangle_bounding_fn,
};
/// Make a change-of-basis matrix.
static inline dmnsn_matrix
dmnsn_triangle_basis(dmnsn_vector vertices[3])
{
// The new vector space has corners at <1, 0, 0>, <0, 1, 0>, and 0,
// corresponding to the basis (ab, ac, ab X ac).
dmnsn_vector ab = dmnsn_vector_sub(vertices[1], vertices[0]);
dmnsn_vector ac = dmnsn_vector_sub(vertices[2], vertices[0]);
dmnsn_vector normal = dmnsn_vector_cross(ab, ac);
return dmnsn_new_matrix4(ab, ac, normal, vertices[0]);
}
dmnsn_object *
dmnsn_new_triangle(dmnsn_pool *pool, dmnsn_vector vertices[3])
{
dmnsn_object *object = dmnsn_new_object(pool);
object->vtable = &dmnsn_triangle_vtable;
object->intrinsic_trans = dmnsn_triangle_basis(vertices);
return object;
}
dmnsn_object *
dmnsn_new_smooth_triangle(dmnsn_pool *pool, dmnsn_vector vertices[3], dmnsn_vector normals[3])
{
dmnsn_matrix P = dmnsn_triangle_basis(vertices);
// Transform the given 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]));
dmnsn_smooth_triangle *triangle = DMNSN_PALLOC(pool, dmnsn_smooth_triangle);
triangle->na = na;
triangle->nab = dmnsn_vector_sub(nb, na);
triangle->nac = dmnsn_vector_sub(nc, na);
dmnsn_object *object = &triangle->object;
dmnsn_init_object(object);
object->vtable = &dmnsn_smooth_triangle_vtable;
object->intrinsic_trans = P;
return object;
}
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