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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 "dimension.h"
/** Optimized ray/triangle intersection test. */
static inline bool
dmnsn_ray_triangle_intersection(dmnsn_line 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. */
static bool
dmnsn_triangle_intersection_fn(const dmnsn_object *object, dmnsn_line 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 *triangle, dmnsn_vector point)
{
return false;
}
/** Smooth triangle type. */
typedef struct {
dmnsn_object object;
dmnsn_vector na, nab, nac;
} dmnsn_smooth_triangle;
/** Smooth triangle intersection callback. */
static bool
dmnsn_smooth_triangle_intersection_fn(const dmnsn_object *object, dmnsn_line 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;
}
/** Make a change-of-basis matrix. */
static inline dmnsn_matrix
dmnsn_triangle_basis(dmnsn_vector vertices[3])
{
/*
* The new vector space has corners at <0, 1, 0>, <0, 0, 1>, 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->intersection_fn = dmnsn_triangle_intersection_fn;
object->inside_fn = dmnsn_triangle_inside_fn;
object->bounding_box.min = dmnsn_zero;
object->bounding_box.max = dmnsn_new_vector(1.0, 1.0, 0.0);
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->intersection_fn = dmnsn_smooth_triangle_intersection_fn;
object->inside_fn = dmnsn_triangle_inside_fn;
object->bounding_box.min = dmnsn_zero;
object->bounding_box.max = dmnsn_new_vector(1.0, 1.0, 0.0);
object->intrinsic_trans = P;
return object;
}
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