From 7b09710392d35fb55b52031d447a542d99fc6b4b Mon Sep 17 00:00:00 2001 From: Tavian Barnes Date: Tue, 19 Aug 2014 17:10:03 -0400 Subject: Modularize the libdimension codebase. --- libdimension/model/objects/sphere.c | 116 ++++++++++++++++++++++++++++++++++++ 1 file changed, 116 insertions(+) create mode 100644 libdimension/model/objects/sphere.c (limited to 'libdimension/model/objects/sphere.c') diff --git a/libdimension/model/objects/sphere.c b/libdimension/model/objects/sphere.c new file mode 100644 index 0000000..e1ca784 --- /dev/null +++ b/libdimension/model/objects/sphere.c @@ -0,0 +1,116 @@ +/************************************************************************* + * Copyright (C) 2009-2014 Tavian Barnes * + * * + * 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 * + * . * + *************************************************************************/ + +/** + * @file + * Spheres. + */ + +#include "internal.h" +#include "internal/polynomial.h" +#include "dimension/model.h" + +/// Sphere intersection callback. +static bool +dmnsn_sphere_intersection_fn(const dmnsn_object *sphere, dmnsn_ray l, + dmnsn_intersection *intersection) +{ + // Solve (x0 + nx*t)^2 + (y0 + ny*t)^2 + (z0 + nz*t)^2 == 1 + double poly[3], x[2]; + poly[2] = dmnsn_vector_dot(l.n, l.n); + poly[1] = 2.0*dmnsn_vector_dot(l.n, l.x0); + poly[0] = dmnsn_vector_dot(l.x0, l.x0) - 1.0; + + size_t n = dmnsn_polynomial_solve(poly, 2, x); + if (n == 0) { + return false; + } + + double t = x[0]; + // Optimize for the case where we're outside the sphere + if (dmnsn_likely(n == 2)) { + t = dmnsn_min(t, x[1]); + } + + intersection->t = t; + intersection->normal = dmnsn_ray_point(l, t); + return true; +} + +/// Sphere inside callback. +static bool +dmnsn_sphere_inside_fn(const dmnsn_object *sphere, dmnsn_vector point) +{ + return point.x*point.x + point.y*point.y + point.z*point.z < 1.0; +} + +/// Helper for sphere bounding box calculation. +static inline double +dmnsn_implicit_dot(double row[4]) +{ + double ret = 0.0; + for (int i = 0; i < 3; ++i) { + ret += row[i]*row[i]; + } + return ret; +} + +/// Sphere bounding callback. +static dmnsn_aabb +dmnsn_sphere_bounding_fn(const dmnsn_object *object, dmnsn_matrix trans) +{ + // Get a tight bound using the quadric representation of a sphere. For + // details, see + // http://tavianator.com/2014/06/exact-bounding-boxes-for-spheres-ellipsoids + + dmnsn_aabb box; + + double cx = trans.n[0][3]; + double dx = sqrt(dmnsn_implicit_dot(trans.n[0])); + box.min.x = cx - dx; + box.max.x = cx + dx; + + double cy = trans.n[1][3]; + double dy = sqrt(dmnsn_implicit_dot(trans.n[1])); + box.min.y = cy - dy; + box.max.y = cy + dy; + + double cz = trans.n[2][3]; + double dz = sqrt(dmnsn_implicit_dot(trans.n[2])); + box.min.z = cz - dz; + box.max.z = cz + dz; + + return box; +} + +/// Sphere vtable. +static const dmnsn_object_vtable dmnsn_sphere_vtable = { + .intersection_fn = dmnsn_sphere_intersection_fn, + .inside_fn = dmnsn_sphere_inside_fn, + .bounding_fn = dmnsn_sphere_bounding_fn, +}; + +dmnsn_object * +dmnsn_new_sphere(dmnsn_pool *pool) +{ + dmnsn_object *sphere = dmnsn_new_object(pool); + sphere->vtable = &dmnsn_sphere_vtable; + return sphere; +} -- cgit v1.2.3