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/*************************************************************************
* Copyright (C) 2009-2010 Tavian Barnes <tavianator@gmail.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/>. *
*************************************************************************/
#include "dimension.h"
#include <math.h>
/*
* Cylinder
*/
/* Cylinder callbacks */
static bool dmnsn_cylinder_intersection_fn(const dmnsn_object *cylinder,
dmnsn_line line,
dmnsn_intersection *intersection);
static bool dmnsn_cylinder_inside_fn(const dmnsn_object *cylinder,
dmnsn_vector point);
/* Payload type */
typedef struct dmnsn_cylinder_payload {
double r1, r2;
bool open;
} dmnsn_cylinder_payload;
/* Allocate a new cylinder object */
dmnsn_object *
dmnsn_new_cylinder(double r1, double r2, bool open)
{
dmnsn_object *cylinder = dmnsn_new_object();
cylinder->intersection_fn = &dmnsn_cylinder_intersection_fn;
cylinder->inside_fn = &dmnsn_cylinder_inside_fn;
cylinder->bounding_box.min = dmnsn_new_vector(-1.0, -1.0, -1.0);
cylinder->bounding_box.max = dmnsn_new_vector(1.0, 1.0, 1.0);
dmnsn_cylinder_payload *payload
= dmnsn_malloc(sizeof(dmnsn_cylinder_payload));
payload->r1 = r1;
payload->r2 = r2;
payload->open = open;
cylinder->ptr = payload;
cylinder->free_fn = &dmnsn_free;
return cylinder;
}
/* Intersections callback for a cylinder */
static bool
dmnsn_cylinder_intersection_fn(const dmnsn_object *cylinder, dmnsn_line l,
dmnsn_intersection *intersection)
{
const dmnsn_cylinder_payload *payload = cylinder->ptr;
double r1 = payload->r1, r2 = payload->r2;
/* Solve (x0 + nx*t)^2 + (z0 + nz*t)^2
== (((r2 - r1)*(y0 + ny*t) + r1 + r2)/2)^2 */
double poly[3], x[2];
poly[2] = l.n.x*l.n.x + l.n.z*l.n.z - l.n.y*l.n.y*(r2 - r1)*(r2 - r1)/4.0;
poly[1] = 2.0*(l.n.x*l.x0.x + l.n.z*l.x0.z)
- l.n.y*(r2 - r1)*(l.x0.y*(r2 - r1) + r2 + r1)/2.0;
poly[0] = l.x0.x*l.x0.x + l.x0.z*l.x0.z
- (l.x0.y*(r2 - r1) + r2 + r1)*(l.x0.y*(r2 - r1) + r2 + r1)/4;
size_t n = dmnsn_solve_polynomial(poly, 2, x);
if (n > 0) {
double t = x[0];
dmnsn_vector p;
if (n == 2) {
t = dmnsn_min(t, x[1]);
p = dmnsn_line_point(l, t);
if (p.y <= -1.0 || p.y >= 1.0) {
t = dmnsn_max(x[0], x[1]);
p = dmnsn_line_point(l, t);
}
} else {
p = dmnsn_line_point(l, t);
}
if (!payload->open && l.n.y) {
/* Test for cap intersections */
double tcap1 = (-1.0 - l.x0.y)/l.n.y;
double tcap2 = (+1.0 - l.x0.y)/l.n.y;
double tcap, r;
dmnsn_vector norm;
if (tcap1 < tcap2) {
tcap = tcap1;
r = r1;
norm = dmnsn_new_vector(0.0, -1.0, 0.0);
} else {
tcap = tcap2;
r = r2;
norm = dmnsn_new_vector(0.0, 1.0, 0.0);
}
dmnsn_vector pcap = dmnsn_line_point(l, tcap);
if (tcap < 0.0 || pcap.x*pcap.x + pcap.z*pcap.z >= r*r) {
if (tcap2 <= tcap1) {
tcap = tcap1;
r = r1;
norm = dmnsn_new_vector(0.0, -1.0, 0.0);
} else {
tcap = tcap2;
r = r2;
norm = dmnsn_new_vector(0.0, 1.0, 0.0);
}
pcap = dmnsn_line_point(l, tcap);
}
if (tcap >= 0.0
&& (tcap < t || p.y <= -1.0 || p.y >= 1.0)
&& pcap.x*pcap.x + pcap.z*pcap.z < r*r)
{
intersection->ray = l;
intersection->t = tcap;
intersection->normal = norm;
intersection->texture = cylinder->texture;
intersection->interior = cylinder->interior;
return true;
}
}
if (t >= 0.0 && p.y > -1.0 && p.y < 1.0) {
dmnsn_vector norm = dmnsn_vector_normalize(
dmnsn_new_vector(p.x, -(r2 - r1)*sqrt(p.x*p.x + p.z*p.z)/2.0, p.z)
);
intersection->ray = l;
intersection->t = t;
intersection->normal = norm;
intersection->texture = cylinder->texture;
intersection->interior = cylinder->interior;
return true;
}
}
return false;
}
/* Inside callback for a cylinder */
static bool
dmnsn_cylinder_inside_fn(const dmnsn_object *cylinder, dmnsn_vector point)
{
const dmnsn_cylinder_payload *payload = cylinder->ptr;
double r1 = payload->r1, r2 = payload->r2;
double r = (point.y*(r2 - r1) + r1 + r2)/2.0;
return point.x*point.x + point.z*point.z < r*r
&& point.y > -1.0 && point.y < 1.0;
}
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