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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
 * Cones/cylinders.
 */

#include "internal/polynomial.h"
#include "dimension/model.h"
#include <math.h>

/// Cone type.
typedef struct dmnsn_cone {
  dmnsn_object object;
  double r1, r2;
} dmnsn_cone;

/// Intersection callback for a cone.
static bool
dmnsn_cone_intersection_fn(const dmnsn_object *object, dmnsn_ray l,
                           dmnsn_intersection *intersection)
{
  const dmnsn_cone *cone = (const dmnsn_cone *)object;
  double r1 = cone->r1, r2 = cone->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)/4.0;

  size_t n = dmnsn_polynomial_solve(poly, 2, x);

  if (n > 0) {
    double t = x[0];
    dmnsn_vector p;
    if (n == 2) {
      t = dmnsn_min(t, x[1]);
      p = dmnsn_ray_point(l, t);

      if (p.y <= -1.0 || p.y >= 1.0) {
        t = dmnsn_max(x[0], x[1]);
        p = dmnsn_ray_point(l, t);
      }
    } else {
      p = dmnsn_ray_point(l, t);
    }

    if (t >= 0.0 && p.y >= -1.0 && p.y <= 1.0) {
      double r = ((r2 - r1)*p.y + r1 + r2)/2.0;
      dmnsn_vector norm = dmnsn_new_vector(p.x, -r*(r2 - r1)/2.0, p.z);
      intersection->t      = t;
      intersection->normal = norm;
      return true;
    }
  }

  return false;
}

/// Inside callback for a cone.
static bool
dmnsn_cone_inside_fn(const dmnsn_object *object, dmnsn_vector point)
{
  const dmnsn_cone *cone = (const dmnsn_cone *)object;
  double r1 = cone->r1, r2 = cone->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;
}

/// Cone bounding callback.
static dmnsn_aabb
dmnsn_cone_bounding_fn(const dmnsn_object *object, dmnsn_matrix trans)
{
  const dmnsn_cone *cone = (const dmnsn_cone *)object;

  double rmax = dmnsn_max(cone->r1, cone->r2);
  dmnsn_aabb box = dmnsn_symmetric_aabb(dmnsn_new_vector(rmax, 1.0, rmax));
  return dmnsn_transform_aabb(trans, box);
}

/// Cone vtable.
static const dmnsn_object_vtable dmnsn_cone_vtable = {
  .intersection_fn = dmnsn_cone_intersection_fn,
  .inside_fn = dmnsn_cone_inside_fn,
  .bounding_fn = dmnsn_cone_bounding_fn,
};

/// Cone cap type.
typedef struct dmnsn_cone_cap {
  dmnsn_object object;
  double r;
} dmnsn_cone_cap;

/// Cone cap intersection function.
static bool
dmnsn_cone_cap_intersection_fn(const dmnsn_object *object, dmnsn_ray l,
                               dmnsn_intersection *intersection)
{
  if (l.n.y != 0.0) {
    const dmnsn_cone_cap *cap = (const dmnsn_cone_cap *)object;
    double r = cap->r;
    double t = -l.x0.y/l.n.y;
    dmnsn_vector p = dmnsn_ray_point(l, t);
    if (t >= 0.0 && p.x*p.x + p.z*p.z <= r*r) {
      intersection->t      = t;
      intersection->normal = dmnsn_new_vector(0.0, -1.0, 0.0);
      return true;
    }
  }

  return false;
}

/// Inside callback for a cone cap.
static bool
dmnsn_cone_cap_inside_fn(const dmnsn_object *object, dmnsn_vector point)
{
  return false;
}

/// Cone cap bounding callback.
static dmnsn_aabb
dmnsn_cone_cap_bounding_fn(const dmnsn_object *object, dmnsn_matrix trans)
{
  const dmnsn_cone_cap *cap = (const dmnsn_cone_cap *)object;
  dmnsn_aabb box = dmnsn_symmetric_aabb(dmnsn_new_vector(cap->r, 0.0, cap->r));
  return dmnsn_transform_aabb(trans, box);
}

/// Cone cap vtable.
static const dmnsn_object_vtable dmnsn_cone_cap_vtable = {
  .intersection_fn = dmnsn_cone_cap_intersection_fn,
  .inside_fn = dmnsn_cone_cap_inside_fn,
  .bounding_fn = dmnsn_cone_cap_bounding_fn,
};

/// Allocate a new cone cap.
dmnsn_object *
dmnsn_new_cone_cap(dmnsn_pool *pool, double r)
{
  dmnsn_cone_cap *cap = DMNSN_PALLOC(pool, dmnsn_cone_cap);
  cap->r = r;

  dmnsn_object *object = &cap->object;
  dmnsn_init_object(object);
  object->vtable = &dmnsn_cone_cap_vtable;
  return object;
}

// Allocate a new cone object
dmnsn_object *
dmnsn_new_cone(dmnsn_pool *pool, double r1, double r2, bool open)
{
  dmnsn_cone *cone = DMNSN_PALLOC(pool, dmnsn_cone);
  cone->r1 = r1;
  cone->r2 = r2;

  dmnsn_object *object = &cone->object;
  dmnsn_init_object(object);
  object->vtable = &dmnsn_cone_vtable;

  if (open) {
    return object;
  }

  // Implement closed cones as a union with the caps
  dmnsn_object *cap1 = dmnsn_new_cone_cap(pool, r1);
  dmnsn_object *cap2 = dmnsn_new_cone_cap(pool, r2);
  cap1->intrinsic_trans = dmnsn_translation_matrix(
    dmnsn_new_vector(0.0, -1.0, 0.0)
  );
  cap2->intrinsic_trans = dmnsn_translation_matrix(
    dmnsn_new_vector(0.0, +1.0, 0.0)
  );
  // Flip the normal around for the top cap
  cap2->intrinsic_trans.n[1][1] = -1.0;

  dmnsn_array *withcaps = DMNSN_PALLOC_ARRAY(pool, dmnsn_object *);
  dmnsn_array_push(withcaps, &cone);
  dmnsn_array_push(withcaps, &cap1);
  dmnsn_array_push(withcaps, &cap2);
  dmnsn_object *cone_cap_union = dmnsn_new_csg_union(pool, withcaps);

  return cone_cap_union;
}