/*
 * Copyright (C) Volition, Inc. 1999.  All rights reserved.
 *
 * All source code herein is the property of Volition, Inc. You may not sell 
 * or otherwise commercially exploit the source or things you created based on the 
 * source.
 *
*/ 




#define MODEL_LIB

#include "cmdline/cmdline.h"
#include "graphics/tmapper.h"
#include "math/fvi.h"
#include "math/vecmat.h"
#include "model/model.h"
#include "model/modelsinc.h"
#include "tracing/tracing.h"
#include "tracing/Monitor.h"



#define TOL		1E-4
#define DIST_TOL	1.0

// Some global variables that get set by model_collide and are used internally for
// checking a collision rather than passing a bunch of parameters around. These are
// not persistant between calls to model_collide

static mc_info		*Mc;				// The mc_info passed into model_collide
	
static polymodel	*Mc_pm;			// The polygon model we're checking
static int			Mc_submodel;	// The current submodel we're checking

static polymodel_instance *Mc_pmi;

static matrix		Mc_orient;		// A matrix to rotate a world point into the current
											// submodel's frame of reference.
static vec3d		Mc_base;			// A point used along with Mc_orient.

static vec3d		Mc_p0;			// The ray origin rotated into the current submodel's frame of reference
static vec3d		Mc_p1;			// The ray end rotated into the current submodel's frame of reference
static float		Mc_mag;			// The length of the ray
static vec3d		Mc_direction;	// A vector from the ray's origin to its end, in the current submodel's frame of reference

static vec3d 		**Mc_point_list = NULL;		// A pointer to the current submodel's vertex list

static float		Mc_edge_time;


void model_collide_free_point_list()
{
	if (Mc_point_list != NULL) {
		vm_free(Mc_point_list);
		Mc_point_list = NULL;
	}
}

// allocate the point list
// NOTE: SHOULD ONLY EVER BE CALLED FROM model_allocate_interp_data()!!!
void model_collide_allocate_point_list(int n_points)
{
	Assert( n_points > 0 );

	if (Mc_point_list != NULL) {
		vm_free(Mc_point_list);
		Mc_point_list = NULL;
	}

	Mc_point_list = (vec3d**) vm_malloc( sizeof(vec3d *) * n_points );

	Verify( Mc_point_list != NULL );
}

// Returns non-zero if vector from p0 to pdir 
// intersects the bounding box.
// hitpos could be NULL, so don't fill it if it is.
int mc_ray_boundingbox( vec3d *min, vec3d *max, vec3d * p0, vec3d *pdir, vec3d *hitpos )
{

	vec3d tmp_hitpos;
	if ( hitpos == NULL )	{
		hitpos = &tmp_hitpos;
	}


	if ( Mc->flags & MC_CHECK_SPHERELINE )	{

		// In the case of a sphere, just increase the size of the box by the radius 
		// of the sphere in all directions.

		vec3d sphere_mod_min, sphere_mod_max;

		sphere_mod_min.xyz.x = min->xyz.x - Mc->radius;
		sphere_mod_max.xyz.x = max->xyz.x + Mc->radius;
		sphere_mod_min.xyz.y = min->xyz.y - Mc->radius;
		sphere_mod_max.xyz.y = max->xyz.y + Mc->radius;
		sphere_mod_min.xyz.z = min->xyz.z - Mc->radius;
		sphere_mod_max.xyz.z = max->xyz.z + Mc->radius;

		return fvi_ray_boundingbox( &sphere_mod_min, &sphere_mod_max, p0, pdir, hitpos );
	} else {
		return fvi_ray_boundingbox( min, max, p0, pdir, hitpos );
	}	
}



// ----- 
// mc_check_face
// nv -- number of vertices
// verts -- actual vertices
// plane_pnt -- A point on the plane.  Could probably use the first vertex.
// plane_norm -- normal of the plane
// uvl_list -- list of uv coords for the poly.
// ntmap -- The tmap index into the model's textures array.
//
// detects whether or not a vector has collided with a polygon.  vector points stored in global
// Mc_p0 and Mc_p1.  Results stored in global mc_info * Mc.

static void mc_check_face(int nv, vec3d **verts, vec3d *plane_pnt, vec3d *plane_norm, uv_pair *uvl_list, int ntmap, ubyte *poly, bsp_collision_leaf* bsp_leaf)
{
	vec3d	hit_point;
	float		dist;
	float		u, v;

	// Check to see if poly is facing away from ray.  If so, don't bother
	// checking it.
	if (!(Mc->flags & MC_COLLIDE_ALL) && vm_vec_dot(&Mc_direction,plane_norm) > 0.0f)	{
		return;
	}

	// Find the intersection of this ray with the plane that the poly
	dist = fvi_ray_plane(NULL, plane_pnt, plane_norm, &Mc_p0, &Mc_direction, 0.0f);

	if ( dist < 0.0f ) return; // If the ray is behind the plane there is no collision
	if ( !(Mc->flags & MC_CHECK_RAY) && (dist > 1.0f) ) return; // The ray isn't long enough to intersect the plane

	// If the ray hits, but a closer intersection has already been found, return
	if (!(Mc->flags & MC_COLLIDE_ALL) && Mc->num_hits && (dist >= Mc->hit_dist ) ) return;

	// Find the hit point
	vm_vec_scale_add( &hit_point, &Mc_p0, &Mc_direction, dist );
	
	// Check to see if the point of intersection is on the plane.  If so, this
	// also finds the uv's where the ray hit.
	if ( fvi_point_face(&hit_point, nv, verts, plane_norm, &u,&v, uvl_list ) )	{
		Mc->hit_dist = dist;

		Mc->hit_point = hit_point;
		Mc->hit_submodel = Mc_submodel;
		Mc->hit_normal = *plane_norm;

		if (Mc->flags & MC_COLLIDE_ALL) {
			Mc->hit_points_all.push_back(hit_point);
			Mc->hit_submodels_all.push_back(Mc_submodel);
		}


		if ( uvl_list )	{
			Mc->hit_u = u;
			Mc->hit_v = v;
			if ( ntmap < 0 ) {
				Mc->hit_bitmap = -1;
			} else {
				Mc->hit_bitmap = Mc_pm->maps[ntmap].textures[TM_BASE_TYPE].GetTexture();			
			}
		}
		
		if(ntmap >= 0){
			Mc->t_poly = poly;
			Mc->f_poly = NULL;
		} else {
			Mc->t_poly = NULL;
			Mc->f_poly = poly;
		}

		Mc->bsp_leaf = bsp_leaf;

//		mprintf(( "Bing!\n" ));

		Mc->num_hits++;
	}
}

// ----------------------------------------------------------------------------------------------------------
// check face with spheres
//
//	inputs:	nv				=>		number of vertices
//				verts			=>		array of vertices
//				plane_pnt	=>		center point in plane (about which radius is measured)
//				face_rad		=>		radius of face 
//				plane_norm	=>		normal of face
static void mc_check_sphereline_face( int nv, vec3d ** verts, vec3d * plane_pnt, vec3d * plane_norm, uv_pair * uvl_list, int ntmap, ubyte *poly, bsp_collision_leaf *bsp_leaf)
{
	vec3d	hit_point;
	float		u, v;
	float		delta_t;			// time sphere takes to cross from one side of plane to the other
	float		face_t;			// time at which face touches plane
									// NOTE all times are normalized so that t = 1.0 at the end of the frame
	int		check_face = 1;		// assume we'll check the face.
	int		check_edges = 1;		// assume we'll check the edges.
	
	// Check to see if poly is facing away from ray.  If so, don't bother
	// checking it.

	if (!(Mc->flags & MC_COLLIDE_ALL) && vm_vec_dot(&Mc_direction,plane_norm) > 0.0f)	{
		return;
	}

	// Find the intersection of this sphere with the plane of the poly
	if ( !fvi_sphere_plane( &hit_point, &Mc_p0, &Mc_direction, Mc->radius, plane_norm, plane_pnt, &face_t, &delta_t ) ) {
		return;
	}

	// If the ray is behind the plane there is no collision
	if (face_t > 1.0f) {
		check_face = 0;
		check_edges = 0;
	} else if (face_t < 0.0f) {
		check_face = 0;

		// check whether sphere can hit edge in allowed time range
		if ( (face_t + delta_t) < 0.0f)
			check_edges = 0;
	}

	// If the ray hits, but a closer intersection has already been found, don't check face
	if (!(Mc->flags & MC_COLLIDE_ALL) && Mc->num_hits && (face_t >= Mc->hit_dist ) ) {
		check_face = 0;		// The ray isn't long enough to intersect the plane
	}


	//vec3d temp_sphere;
	//vec3d temp_dir;
	//float temp_dist;
	// DA 11/5/97  Above is used to test distance between hit_point and sphere_hit_point.
	// This can be as large as 0.003 on a unit sphere.  I suspect that with larger spheres,
	// both the relative and absolute error decrease, but this should still be checked for the
	// case of larger spheres (about 5-10 units).  The error also depends on the geometry of the 
	// object we're colliding against, but I think to a lesser degree.

	if ( check_face )	{
		// Find the time of the sphere surface touches the plane
		// If this is within the collision window, check to see if we hit a face
		if ( fvi_point_face(&hit_point, nv, verts, plane_norm, &u, &v, uvl_list) ) {

			Mc->hit_dist = face_t;		
			Mc->hit_point = hit_point;
			Mc->hit_normal = *plane_norm;
			Mc->hit_submodel = Mc_submodel;			
			Mc->edge_hit = false;

			if (Mc->flags & MC_COLLIDE_ALL) {
				Mc->hit_points_all.push_back(hit_point);
				Mc->hit_submodels_all.push_back(Mc_submodel);
			}

			if ( uvl_list )	{
				Mc->hit_u = u;
				Mc->hit_v = v;
				if ( ntmap < 0 ) {
					Mc->hit_bitmap = -1;
				} else {
					Mc->hit_bitmap = Mc_pm->maps[ntmap].textures[TM_BASE_TYPE].GetTexture();			
				}
			}

			if(ntmap >= 0){
				Mc->t_poly = poly;
				Mc->f_poly = NULL;
			} else {
				Mc->t_poly = NULL;
				Mc->f_poly = poly;
			}

			Mc->bsp_leaf = bsp_leaf;

			Mc->num_hits++;
			check_edges = 0;
			/*
			vm_vec_scale_add( &temp_sphere, &Mc_p0, &Mc_direction, Mc->hit_dist );
			temp_dist = vm_vec_dist( &temp_sphere, &hit_point );
			if ( (temp_dist - DIST_TOL > Mc->radius) || (temp_dist + DIST_TOL < Mc->radius) ) {
				// get Andsager
				//mprintf(("Estimated radius error: Estimate %f, actual %f Mc->radius\n", temp_dist, Mc->radius));
			}
			vm_vec_sub( &temp_dir, &hit_point, &temp_sphere );
			// Assert( vm_vec_dot( &temp_dir, &Mc_direction ) > 0 );
			*/
		}
	}


	if ( check_edges ) {
		// Either (face_t) is out of range or we miss the face
		// Check for sphere hitting edge

		// If checking shields, we *still* need to check edges

		// this is where we need another test to cull checking for edges
		// PUT TEST HERE

		// check each edge to see if we hit, find the closest edge
		// Mc->hit_dist stores the best edge time of *all* faces
		float sphere_time;
		if ( fvi_polyedge_sphereline(&hit_point, &Mc_p0, &Mc_direction, Mc->radius, nv, verts, &sphere_time)) {
			Assert( sphere_time >= 0.0f );
			/*
			vm_vec_scale_add( &temp_sphere, &Mc_p0, &Mc_direction, sphere_time );
			temp_dist = vm_vec_dist( &temp_sphere, &hit_point );
			if ( (temp_dist - DIST_TOL > Mc->radius) || (temp_dist + DIST_TOL < Mc->radius) ) {
				// get Andsager
				//mprintf(("Estimated radius error: Estimate %f, actual %f Mc->radius\n", temp_dist, Mc->radius));
			}
			vm_vec_sub( &temp_dir, &hit_point, &temp_sphere );
//			Assert( vm_vec_dot( &temp_dir, &Mc_direction ) > 0 );
			*/

			if ((Mc->flags & MC_COLLIDE_ALL) || (Mc->num_hits==0) || (sphere_time < Mc->hit_dist) ) {
				// This is closer than best so far
				Mc->hit_dist = sphere_time;
				Mc->hit_point = hit_point;
				Mc->hit_submodel = Mc_submodel;
				Mc->edge_hit = true;

				if (Mc->flags & MC_COLLIDE_ALL) {
					Mc->hit_points_all.push_back(hit_point);
					Mc->hit_submodels_all.push_back(Mc_submodel);
				}

				if ( ntmap < 0 ) {
					Mc->hit_bitmap = -1;
				} else {
					Mc->hit_bitmap = Mc_pm->maps[ntmap].textures[TM_BASE_TYPE].GetTexture();			
				}

				if(ntmap >= 0){
					Mc->t_poly = poly;
					Mc->f_poly = NULL;
				} else {
					Mc->t_poly = NULL;
					Mc->f_poly = poly;
				}

				Mc->num_hits++;

			//	nprintf(("Physics", "edge sphere time: %f, normal: (%f, %f, %f) hit_point: (%f, %f, %f)\n", sphere_time,
			//		Mc->hit_normal.xyz.x, Mc->hit_normal.xyz.y, Mc->hit_normal.xyz.z,
			//		hit_point.xyz.x, hit_point.xyz.y, hit_point.xyz.z));
			} else  {	// Not best so far
				Assert(Mc->num_hits>0);
				Mc->num_hits++;
			}
		}
	}
}

int model_collide_parse_bsp_defpoints(ubyte * p)
{
	uint n;
	uint nverts = uw(p+8);	
	uint offset = uw(p+16);	

	ubyte * normcount = p+20;
	vec3d *src = vp(p+offset);

	model_collide_allocate_point_list(nverts);

	Assert( Mc_point_list != NULL );

	for (n=0; n<nverts; n++ ) {
		Mc_point_list[n] = src;

		src += normcount[n]+1;
	} 

	return nverts;
}

void model_collide_bsp_poly(bsp_collision_tree *tree, int leaf_index)
{
	int i;
	int tested_leaf = leaf_index;
	uv_pair uvlist[TMAP_MAX_VERTS];
	vec3d *points[TMAP_MAX_VERTS];

	while ( tested_leaf >= 0 ) {
		bsp_collision_leaf *leaf = &tree->leaf_list[tested_leaf];

		bool flat_poly = false;
		int vert_start = leaf->vert_start;
		int nv = leaf->num_verts;

		if ( leaf->tmap_num < MAX_MODEL_TEXTURES ) {
			if ( (!(Mc->flags & MC_CHECK_INVISIBLE_FACES)) && (Mc_pm->maps[leaf->tmap_num].textures[TM_BASE_TYPE].GetTexture() < 0) )	{
				// Don't check invisible polygons.
				//SUSHI: Unless $collide_invisible is set.
				if (!(Mc_pm->submodel[Mc_submodel].flags[Model::Submodel_flags::Collide_invisible]))
					return;
			}
		} else {
			flat_poly = true;
		}

		int vert_num;
		for ( i = 0; i < nv; ++i ) {
			vert_num = tree->vert_list[vert_start+i].vertnum;
			points[i] = &tree->point_list[vert_num];

			uvlist[i].u = tree->vert_list[vert_start+i].u;
			uvlist[i].v = tree->vert_list[vert_start+i].v;
		}

		if ( flat_poly ) {
			if ( Mc->flags & MC_CHECK_SPHERELINE ) {
				mc_check_sphereline_face(nv, points, points[0], &leaf->plane_norm, nullptr, -1, nullptr, leaf);
			} else {
				mc_check_face(nv, points, points[0], &leaf->plane_norm, nullptr, -1, nullptr, leaf);
			}
		} else {
			if ( Mc->flags & MC_CHECK_SPHERELINE ) {
				mc_check_sphereline_face(nv, points, points[0], &leaf->plane_norm, uvlist, leaf->tmap_num, nullptr, leaf);
			} else {
				mc_check_face(nv, points, points[0], &leaf->plane_norm, uvlist, leaf->tmap_num, nullptr, leaf);
			}
		}

		tested_leaf = leaf->next;
	}
}

void model_collide_bsp(bsp_collision_tree *tree, int node_index)
{
	if ( tree->node_list == NULL || tree->n_verts <= 0) {
		return;
	}

	bsp_collision_node *node = &tree->node_list[node_index];
	vec3d hitpos;

	// check the bounding box of this node. if it passes, check left and right children
	if ( mc_ray_boundingbox( &node->min, &node->max, &Mc_p0, &Mc_direction, &hitpos ) ) {
		if ( !(Mc->flags & MC_CHECK_RAY) && (vm_vec_dist(&hitpos, &Mc_p0) > Mc_mag) ) {
			// The ray isn't long enough to intersect the bounding box
			return;
		}

		if ( node->leaf >= 0 ) {
			model_collide_bsp_poly(tree, node->leaf);
		} else {
			if ( node->back >= 0 ) model_collide_bsp(tree, node->back);
			if ( node->front >= 0 ) model_collide_bsp(tree, node->front);
		}
	}
}

void model_collide_parse_bsp_tmappoly(bsp_collision_leaf *leaf, SCP_vector<model_tmap_vert> *vert_buffer, void *model_ptr)
{
	ubyte *p = (ubyte *)model_ptr;

	uint i;
	uint nv;

	nv = uw(p + TMAP_NVERTS);

	if ( nv > TMAP_MAX_VERTS ) {
		Int3();
		return;
	}

	int tmap_num = w(p + TMAP_TEXNUM);

	Assert(tmap_num >= 0 && tmap_num < MAX_MODEL_TEXTURES);

	auto verts = reinterpret_cast<model_tmap_vert_old*>(&p[TMAP_VERTS]);

	leaf->tmap_num = (ubyte)tmap_num;
	leaf->num_verts = (ubyte)nv;
	leaf->vert_start = (int)vert_buffer->size();

	vec3d *plane_norm = vp(p + TMAP_NORMAL);

	leaf->plane_norm = *plane_norm;

	for ( i = 0; i < nv; ++i ) {
		vert_buffer->push_back(model_tmap_vert(verts[i]));
	}
}

/**
* @brief Generates BSP leaf and vertex buffer to check against a bsp collision for a TMAP2 chunk.
* 
* @param[out] leaf Generated BSP leaf.
* @param[out] vert_buffer Vertex buffer forming the polygon being checked against.
* @param[in] model_ptr Buffer of BSP data from model buffer.
*/
void model_collide_parse_bsp_tmap2poly(bsp_collision_leaf* leaf, SCP_vector<model_tmap_vert>* vert_buffer, void* model_ptr)
{
	auto p = (ubyte*)model_ptr;

	uint i;
	uint nv;
	int tmap_num;
	vec3d* plane_norm;
	model_tmap_vert* verts;

	nv = uw(p + TMAP2_NVERTS);

	if (nv > TMAP_MAX_VERTS) {
		Error(LOCATION,"Model contains TMAP2 chunk with more than %d vertices!", TMAP_MAX_VERTS);
		return;
	}

	tmap_num = w(p + TMAP2_TEXNUM);

	if (tmap_num < 0 || tmap_num >= MAX_MODEL_TEXTURES) {
		Error(LOCATION, "Model contains TMAP2 chunk with invalid texture id (%d)!", tmap_num);
		return;
	}

	verts = reinterpret_cast<model_tmap_vert*>(p + TMAP2_VERTS);

	leaf->tmap_num = (ubyte)tmap_num;
	leaf->num_verts = (ubyte)nv;
	leaf->vert_start = (int)vert_buffer->size();

	plane_norm = vp(p + TMAP2_NORMAL);

	leaf->plane_norm = *plane_norm;

	for (i = 0; i < nv; ++i) {
		vert_buffer->push_back(verts[i]);
	}
}

void model_collide_parse_bsp_flatpoly(bsp_collision_leaf *leaf, SCP_vector<model_tmap_vert> *vert_buffer, void *model_ptr)
{
	ubyte *p = (ubyte *)model_ptr;

	uint i;
	uint nv;
	short *verts;

	nv = uw(p+36);

	if ( nv > TMAP_MAX_VERTS ) {
		Int3();
		return;
	}

	verts = (short *)(p+44);

	leaf->tmap_num = 255;
	leaf->num_verts = (ubyte)nv;
	leaf->vert_start = (int)vert_buffer->size();

	vec3d *plane_norm = vp(p+8);

	leaf->plane_norm = *plane_norm;

	model_tmap_vert vert;

	for ( i = 0; i < nv; ++i ) {
		vert.vertnum = verts[i*2];
		vert.normnum = 0;
		vert.u = 0.0f;
		vert.v = 0.0f;

		vert_buffer->push_back(vert);
	}
}

void model_collide_parse_bsp(bsp_collision_tree *tree, void *model_ptr, int version)
{
	TRACE_SCOPE(tracing::ModelParseBSPTree);

	ubyte *p = (ubyte *)model_ptr;
	ubyte *next_p;

	int chunk_type = w(p);
	int chunk_size = w(p+4);

	int next_chunk_type;
	int next_chunk_size;

	Assert(chunk_type == OP_DEFPOINTS);

	int n_verts = model_collide_parse_bsp_defpoints(p);

	if ( n_verts <= 0) {
		tree->point_list = NULL;
		tree->n_verts = 0;

		tree->n_nodes = 0;
		tree->node_list = NULL;

		tree->n_leaves = 0;
		tree->leaf_list = NULL;

		// finally copy the vert list.
		tree->vert_list = NULL;

		return;
	}

	p += chunk_size;

	bsp_collision_node new_node;
	bsp_collision_leaf new_leaf{ vmd_zero_vector, 0, 0, 0, 0 };

	SCP_vector<bsp_collision_node> node_buffer;
	SCP_vector<bsp_collision_leaf> leaf_buffer;
	SCP_vector<model_tmap_vert> vert_buffer;

	SCP_map<size_t, ubyte*> bsp_datap;

	node_buffer.push_back(new_node);

	size_t i = 0;
	vec3d *min;
	vec3d *max;

	bsp_datap[i] = p;

	while ( i < node_buffer.size() ) {
		p = bsp_datap[i];

		chunk_type = w(p);
		chunk_size = w(p+4);
		int front_offset, back_offset;
		switch ( chunk_type ) {
		case OP_SORTNORM:
			if ( version >= 2000 ) {
				min = vp(p+56);
				max = vp(p+68);

				node_buffer[i].min = *min;
				node_buffer[i].max = *max;
			}

			node_buffer[i].leaf = -1;
			node_buffer[i].front = -1;
			node_buffer[i].back = -1;

			front_offset = w(p + 36);
			if (front_offset) {
				next_chunk_type = w(p + front_offset);

				if ( next_chunk_type != OP_EOF ) {
					node_buffer.push_back(new_node);
					node_buffer[i].front = (int)(node_buffer.size() - 1);
					bsp_datap[node_buffer[i].front] = p + front_offset;
				}
			}

			back_offset = w(p + 40);
			if (back_offset) {
				next_chunk_type = w(p + back_offset);
				
				if ( next_chunk_type != OP_EOF ) {
					node_buffer.push_back(new_node);
					node_buffer[i].back = (int)(node_buffer.size() - 1);
					bsp_datap[node_buffer[i].back] = p + back_offset;
				}
			}

			next_p = p + chunk_size;
			next_chunk_type = w(next_p);

			Assert( next_chunk_type == OP_EOF );

			++i;
			break;
		case OP_SORTNORM2:
			min = vp(p + 16);
			max = vp(p + 28);

			node_buffer[i].min = *min;
			node_buffer[i].max = *max;

			node_buffer[i].leaf = -1;
			node_buffer[i].front = -1;
			node_buffer[i].back = -1;

			front_offset = w(p + 8);
			if (front_offset) {
				next_chunk_type = w(p + front_offset);

				if (next_chunk_type != OP_EOF) {
					node_buffer.push_back(new_node);
					node_buffer[i].front = (int)(node_buffer.size() - 1);
					bsp_datap[node_buffer[i].front] = p + front_offset;
				}
			}

			back_offset = w(p + 12);
			if (back_offset) {
				next_chunk_type = w(p + back_offset);

				if (next_chunk_type != OP_EOF) {
					node_buffer.push_back(new_node);
					node_buffer[i].back = (int)(node_buffer.size() - 1);
					bsp_datap[node_buffer[i].back] = p + back_offset;
				}
			}

			next_p = p + chunk_size;
			next_chunk_type = w(next_p);

			++i;
			break;
		case OP_BOUNDBOX:
			min = vp(p+8);
			max = vp(p+20);

			node_buffer[i].min = *min;
			node_buffer[i].max = *max;

			node_buffer[i].front = -1;
			node_buffer[i].back = -1;
			node_buffer[i].leaf = -1;

			next_p = p + chunk_size;
			next_chunk_type = w(next_p);
			next_chunk_size = w(next_p+4);

			if (next_chunk_type != OP_EOF &&
				(next_chunk_type == OP_TMAPPOLY || next_chunk_type == OP_FLATPOLY)) {
				new_leaf.next = -1;

				node_buffer[i].leaf = (int)leaf_buffer.size();	// get index of where our poly list starts in the leaf buffer

				while ( next_chunk_type != OP_EOF ) {
					if ( next_chunk_type == OP_TMAPPOLY ) {
						model_collide_parse_bsp_tmappoly(&new_leaf, &vert_buffer, next_p);
					} else if ( next_chunk_type == OP_FLATPOLY ) {
						model_collide_parse_bsp_flatpoly(&new_leaf, &vert_buffer, next_p);
					} else {
						Int3();
					}

					// add another polygon center
					vec3d center = vmd_zero_vector;
					for (int j = 0; j < new_leaf.num_verts; j++) {
						center += *Mc_point_list[vert_buffer[new_leaf.vert_start + j].vertnum];
					}
					tree->poly_centers.push_back(center / (float)new_leaf.num_verts);

					leaf_buffer.push_back(new_leaf);

					leaf_buffer.back().next = (int)leaf_buffer.size();

					next_p += next_chunk_size;
					next_chunk_type = w(next_p);
					next_chunk_size = w(next_p+4);
				}

				leaf_buffer.back().next = -1;
			}

			Assert(next_chunk_type == OP_EOF);

			++i;
			break;
		case OP_TMAP2POLY:
			min = vp(p + 8);
			max = vp(p + 20);

			node_buffer[i].min = *min;
			node_buffer[i].max = *max;

			node_buffer[i].front = -1;
			node_buffer[i].back = -1; 
			node_buffer[i].leaf = (int)leaf_buffer.size();

			model_collide_parse_bsp_tmap2poly(&new_leaf, &vert_buffer, p);

			// add another polygon center
			vec3d center = vmd_zero_vector;
			for (int j = 0; j < new_leaf.num_verts; j++) {
				center += *Mc_point_list[vert_buffer[new_leaf.vert_start + j].vertnum];				
			}
			tree->poly_centers.push_back(center / (float)new_leaf.num_verts);

			leaf_buffer.push_back(new_leaf);

			leaf_buffer.back().next = -1;

			++i;
			break;
		}
	}

	// copy point list
	Assert(n_verts != -1);

	tree->point_list = (vec3d*)vm_malloc(sizeof(vec3d) * n_verts);

	for ( i = 0; i < (size_t)n_verts; ++i ) {
		tree->point_list[i] = *Mc_point_list[i];
	}

	tree->n_verts = n_verts;

	// copy node info. this might be a good time to organize the nodes into a cache efficient tree layout.
	tree->n_nodes = (int)node_buffer.size();
	tree->node_list = (bsp_collision_node*)vm_malloc(sizeof(bsp_collision_node) * node_buffer.size());
	memcpy(tree->node_list, &node_buffer[0], sizeof(bsp_collision_node) * node_buffer.size());
	node_buffer.clear();

	// copy leaves.
	tree->n_leaves = (int)leaf_buffer.size();
	tree->leaf_list = (bsp_collision_leaf*)vm_malloc(sizeof(bsp_collision_leaf) * leaf_buffer.size());
	memcpy(tree->leaf_list, &leaf_buffer[0], sizeof(bsp_collision_leaf) * leaf_buffer.size());
	leaf_buffer.clear();

	// finally copy the vert list.
	tree->vert_list = (model_tmap_vert*)vm_malloc(sizeof(model_tmap_vert) * vert_buffer.size());
	memcpy(tree->vert_list, &vert_buffer[0], sizeof(model_tmap_vert) * vert_buffer.size());
	vert_buffer.clear();
}

bool mc_shield_check_common(shield_tri	*tri)
{
	vec3d * points[3];
	vec3d hitpoint;
	 
	float dist;
	float sphere_check_closest_shield_dist = FLT_MAX;

	// Check to see if Mc_pmly is facing away from ray.  If so, don't bother
	// checking it.
	if (vm_vec_dot(&Mc_direction,&tri->norm) > 0.0f)	{
		return false;
	}
	// get the vertices in the form the next function wants them
	for (int j = 0; j < 3; j++ )
		points[j] = &Mc_pm->shield.verts[tri->verts[j]].pos;

	if (!(Mc->flags & MC_CHECK_SPHERELINE) ) {	// Don't do this test for sphere colliding against shields
		// Find the intersection of this ray with the plane that the Mc_pmly
		// lies in
		dist = fvi_ray_plane(NULL, points[0],&tri->norm,&Mc_p0,&Mc_direction,0.0f);

		if ( dist < 0.0f ) return false; // If the ray is behind the plane there is no collision
		if ( !(Mc->flags & MC_CHECK_RAY) && (dist > 1.0f) ) return false; // The ray isn't long enough to intersect the plane

		// Find the hit Mc_pmint
		vm_vec_scale_add( &hitpoint, &Mc_p0, &Mc_direction, dist );
	
		// Check to see if the Mc_pmint of intersection is on the plane.  If so, this
		// also finds the uv's where the ray hit.
		if ( fvi_point_face(&hitpoint, 3, points, &tri->norm, NULL,NULL,NULL ) )	{
			Mc->hit_dist = dist;
			Mc->shield_hit_tri = (int)(tri - Mc_pm->shield.tris);
			Mc->hit_point = hitpoint;
			Mc->hit_normal = tri->norm;
			Mc->hit_submodel = -1;
			Mc->num_hits++;
			return true;		// We hit, so we're done
		}
	} else {		// Sphere check against shield
					// This needs to look at *all* shield tris and not just return after the first hit

		// HACK HACK!! The 10000.0 is the face radius, I didn't know this,
		// so I'm assume 10000 would be as big as ever.
		mc_check_sphereline_face(3, points, points[0], &tri->norm, NULL, 0, NULL, NULL);
		if (Mc->num_hits && Mc->hit_dist < sphere_check_closest_shield_dist) {

			// same behavior whether face or edge
			// normal, edge_hit, hit_point all updated thru sphereline_face
			sphere_check_closest_shield_dist = Mc->hit_dist;
			Mc->shield_hit_tri = (int)(tri - Mc_pm->shield.tris);
			Mc->hit_submodel = -1;
			Mc->num_hits++;
			return true;		// We hit, so we're done
		}
	} // Mc->flags & MC_CHECK_SPHERELINE else

	return false;
}

bool mc_check_sldc(int offset)
{
	//ShivanSpS - Changed the type char for a type int (Now SLC2)
	if (offset > Mc_pm->sldc_size - 5) //no way is this big enough
		return false;

	int* type_p = (int*)(Mc_pm->shield_collision_tree + offset);

	// not used
	//int *size_p = (int *)(Mc_pm->shield_collision_tree+offset+4);
	// split and polygons
	auto* minbox_p = (vec3d*)(Mc_pm->shield_collision_tree + offset + 8);
	auto* maxbox_p = (vec3d*)(Mc_pm->shield_collision_tree + offset + 20);

	// split
	auto* front_offset_p = (unsigned int*)(Mc_pm->shield_collision_tree + offset + 32);
	auto* back_offset_p = (unsigned int*)(Mc_pm->shield_collision_tree + offset + 36);

	// polygons
	auto* num_polygons_p = (unsigned int*)(Mc_pm->shield_collision_tree + offset + 32);

	auto* shld_polys = (unsigned int*)(Mc_pm->shield_collision_tree + offset + 36);



	// see if it fits inside our bbox
	if (!mc_ray_boundingbox(minbox_p, maxbox_p, &Mc_p0, &Mc_direction, NULL)) {
		return false;
	}

	if (*type_p == 0) // SPLIT
	{
		return mc_check_sldc(offset + *front_offset_p) || mc_check_sldc(offset + *back_offset_p);
	}
	else
	{
		// poly list
		shield_tri* tri;
		for (unsigned int i = 0; i < *num_polygons_p; i++)
		{
			tri = &Mc_pm->shield.tris[shld_polys[i]];

			mc_shield_check_common(tri);

		} // for (unsigned int i = 0; i < leaf->num_polygons; i++)
	}

	// shouldn't be reached
	return false;
}

// checks a vector collision against a ships shield (if it has shield points defined).
void mc_check_shield()
{
	int i;


	if ( Mc_pm->shield.ntris < 1 )
		return;
	if (Mc_pm->shield_collision_tree)
	{
		mc_check_sldc(0); // see if we hit the SLDC
	}
	else
	{				
		for (i = 0; i < Mc_pm->shield.ntris; i++) {
			mc_shield_check_common(&Mc_pm->shield.tris[i]);
		}
	}//model has shield_collsion_tree
}


// This function recursively checks a submodel and its children
// for a collision with a vector.
void mc_check_subobj( int mn )
{
	vec3d tempv;
	vec3d hitpt;		// used in bounding box check
	bsp_info * sm;
	int i;

	Assert( mn >= 0 );
	Assert( mn < Mc_pm->n_models );
	if ( (mn < 0) || (mn>=Mc_pm->n_models) ) return;
	
	sm = &Mc_pm->submodel[mn];
	if (sm->flags[Model::Submodel_flags::No_collisions]) return; // don't do collisions
	if (sm->flags[Model::Submodel_flags::Nocollide_this_only]) goto NoHit; // Don't collide for this model, but keep checking others

	// Rotate the world check points into the current subobject's 
	// frame of reference.
	// After this block, Mc_p0, Mc_p1, Mc_direction, and Mc_mag are correct
	// and relative to this subobjects' frame of reference.
	vm_vec_sub(&tempv, Mc->p0, &Mc_base);
	vm_vec_rotate(&Mc_p0, &tempv, &Mc_orient);

	vm_vec_sub(&tempv, Mc->p1, &Mc_base);
	vm_vec_rotate(&Mc_p1, &tempv, &Mc_orient);
	vm_vec_sub(&Mc_direction, &Mc_p1, &Mc_p0);

	// bail early if no ray exists
	if ( IS_VEC_NULL(&Mc_direction) ) {
		return;
	}

	if (Mc_pm->detail[0] == mn)	{
		// Quickly bail if we aren't inside the full model bbox
		if (!mc_ray_boundingbox( &Mc_pm->mins, &Mc_pm->maxs, &Mc_p0, &Mc_direction, NULL))	{
			return;
		}

		// If we are checking the root submodel, then we might want to check	
		// the shield at this point
		if ((Mc->flags & MC_CHECK_SHIELD) && (Mc_pm->shield.ntris > 0 )) {
			mc_check_shield();
			return;
		}
	}

	if (!(Mc->flags & MC_CHECK_MODEL)) {
		return;
	}
	
	Mc_submodel = mn;

	// Check if the ray intersects this subobject's bounding box
	if ( mc_ray_boundingbox(&sm->min, &sm->max, &Mc_p0, &Mc_direction, &hitpt) ) {
		if (Mc->flags & MC_ONLY_BOUND_BOX) {
			float dist = vm_vec_dist( &Mc_p0, &hitpt );

			// If the ray is behind the plane there is no collision
			if (dist < 0.0f) {
				goto NoHit;
			}

			// The ray isn't long enough to intersect the plane
			if ( !(Mc->flags & MC_CHECK_RAY) && (dist > Mc_mag) ) {
				goto NoHit;
			}

			// If the ray hits, but a closer intersection has already been found, return
			if ( Mc->num_hits && (dist >= Mc->hit_dist) ) {
				goto NoHit;
			}

			Mc->hit_dist = dist;
			Mc->hit_point = hitpt;
			Mc->hit_submodel = Mc_submodel;
			Mc->hit_bitmap = -1;
			Mc->num_hits++;
		} else {
			// The ray intersects this bounding box, so we have to check all the
			// polygons in this submodel.
			if (Mc->lod > 0 && sm->num_details > 0) {
				bsp_info* lod_sm = sm;

				for (i = Mc->lod - 1; i >= 0; i--) {
					if (sm->details[i] != -1) {
						lod_sm = &Mc_pm->submodel[sm->details[i]];

						// mprintf(("Checking %s collision for %s using %s instead\n", Mc_pm->filename, sm->name,
						// lod_sm->name));
						break;
					}
				}

				model_collide_bsp(model_get_bsp_collision_tree(lod_sm->collision_tree_index), 0);
			} else {
				model_collide_bsp(model_get_bsp_collision_tree(sm->collision_tree_index), 0);
			}
		}
	}

NoHit:

	// If we're only checking one submodel, return
	if (Mc->flags & MC_SUBMODEL)	{
		return;
	}

	
	// If this subobject doesn't have any children, we're done checking it.
	if ( sm->num_children < 1 ) return;
	
	// Save instance (Mc_orient, Mc_base, Mc_point_base)
	matrix saved_orient = Mc_orient;
	vec3d saved_base = Mc_base;
	
	// Check all of this subobject's children
	i = sm->first_child;
	while ( i >= 0 )	{
		auto csm = &Mc_pm->submodel[i];
		matrix instance_orient = vmd_identity_matrix;
		vec3d instance_offset = csm->offset;
		bool blown_off = false;
		bool collision_checked = false;
		
		if ( Mc_pmi ) {
			auto csmi = &Mc_pmi->submodel[i];
			instance_orient = csmi->canonical_orient;
			vm_vec_add2(&instance_offset, &csmi->canonical_offset);

			blown_off = csmi->blown_off;
			collision_checked = csmi->collision_checked;
		}

		// Don't check it or its children if it is destroyed
		// or if it's set to no collision
		if ( !blown_off && !collision_checked && !csm->flags[Model::Submodel_flags::No_collisions] )	{
			vm_vec_unrotate(&Mc_base, &instance_offset, &saved_orient);
			vm_vec_add2(&Mc_base, &saved_base);

			vm_matrix_x_matrix(&Mc_orient, &saved_orient, &instance_orient);

			mc_check_subobj( i );
		}

		i = csm->next_sibling;
	}

}

MONITOR(NumFVI)

// See model.h for usage.   I don't want to put the
// usage here because you need to see the #defines and structures
// this uses while reading the help.   
int model_collide(mc_info *mc_info_obj)
{
	Mc = mc_info_obj;

	MONITOR_INC(NumFVI,1);

	Mc->num_hits = 0;				// How many collisions were found
	Mc->shield_hit_tri = -1;	// Assume we won't hit any shield polygons
	Mc->hit_bitmap = -1;
	Mc->edge_hit = false;

	if ( (Mc->flags & MC_CHECK_SHIELD) && (Mc->flags & MC_CHECK_MODEL) )	{
		Error( LOCATION, "Checking both shield and model!\n" );
		return 0;
	}

	//Fill in some global variables that all the model collide routines need internally.
	Mc_pm = model_get(Mc->model_num);
	Mc_orient = *Mc->orient;
	Mc_base = *Mc->pos;
	Mc_mag = vm_vec_dist( Mc->p0, Mc->p1 );
	Mc_edge_time = FLT_MAX;

	if ( Mc->model_instance_num >= 0 ) {
		Mc_pmi = model_get_instance(Mc->model_instance_num);
	} else {
		Mc_pmi = NULL;
	}

	// DA 11/19/98 - disable this check for rotating submodels
	// Don't do check if for very small movement
//	if (Mc_mag < 0.01f) {
//		return 0;
//	}

	float model_radius;		// How big is the model we're checking against
	int first_submodel;		// Which submodel gets returned as hit if MC_ONLY_SPHERE specified

	if ( (Mc->flags & MC_SUBMODEL) || (Mc->flags & MC_SUBMODEL_INSTANCE) )	{
		first_submodel = Mc->submodel_num;
		model_radius = Mc_pm->submodel[first_submodel].rad;
	} else {
		first_submodel = Mc_pm->detail[0];
		model_radius = Mc_pm->rad;
	}

	if ( Mc->flags & MC_CHECK_SPHERELINE ) {
		if ( Mc->radius <= 0.0f ) {
			Warning(LOCATION, "Attempting to collide with a sphere, but the sphere's radius is <= 0.0f!\n\n(model file is %s; submodel is %d, mc_flags are %d)", Mc_pm->filename, first_submodel, Mc->flags);
			return 0;
		}

		// Do a quick check on the Bounding Sphere
		if (fvi_segment_sphere(&Mc->hit_point_world, Mc->p0, Mc->p1, Mc->pos, model_radius+Mc->radius) )	{
			if ( Mc->flags & MC_ONLY_SPHERE )	{
				Mc->hit_point = Mc->hit_point_world;
				Mc->hit_submodel = first_submodel;
				Mc->num_hits++;
				return (Mc->num_hits > 0);
			}
			// continue checking polygons.
		} else {
			return 0;
		}
	} else {
		int r;

		// Do a quick check on the Bounding Sphere
		if ( Mc->flags & MC_CHECK_RAY ) {
			r = fvi_ray_sphere(&Mc->hit_point_world, Mc->p0, Mc->p1, Mc->pos, model_radius);
		} else {
			r = fvi_segment_sphere(&Mc->hit_point_world, Mc->p0, Mc->p1, Mc->pos, model_radius);
		}
		if (r) {
			if ( Mc->flags & MC_ONLY_SPHERE ) {
				Mc->hit_point = Mc->hit_point_world;
				Mc->hit_submodel = first_submodel;
				Mc->num_hits++;
				return (Mc->num_hits > 0);
			}
			// continue checking polygons.
		} else {
			return 0;
		}

	}

	if ( Mc->flags & MC_SUBMODEL )	{
		// Check only one subobject
		mc_check_subobj( Mc->submodel_num );
		// Check submodel and any children
	} else if (Mc->flags & MC_SUBMODEL_INSTANCE) {
		mc_check_subobj(Mc->submodel_num);
	} else {
		// Check all the the highest detail model polygons and subobjects for intersections

		// Don't check it or its children if it is destroyed
		if ( Mc_pmi ) {
			if ( !Mc_pmi->submodel[Mc_pm->detail[0]].blown_off ) {
				mc_check_subobj(Mc_pm->detail[0]);
			}
		} else {
			mc_check_subobj(Mc_pm->detail[0]);
		}
	}


	//If we found a hit, then rotate it into world coordinates	
	if ( Mc->num_hits )	{
		if ( Mc->flags & MC_SUBMODEL )	{
			// If we're just checking one submodel, don't use normal instancing to find world points
			vm_vec_unrotate(&Mc->hit_point_world, &Mc->hit_point, Mc->orient);
			vm_vec_add2(&Mc->hit_point_world, Mc->pos);
		} else {
			if ( Mc_pmi ) {
				model_instance_local_to_global_point(&Mc->hit_point_world, &Mc->hit_point, Mc_pm, Mc_pmi, Mc->hit_submodel, Mc->orient, Mc->pos);
			} else {
				model_local_to_global_point(&Mc->hit_point_world, &Mc->hit_point, Mc_pm, Mc->hit_submodel, Mc->orient, Mc->pos);
			}
		}
		
		// do the same for the list of hitpoints, if necessary
		if (Mc->flags & MC_COLLIDE_ALL) {
			for (size_t i = 0; i < Mc->hit_points_all.size(); i++) {
				if (Mc->flags & MC_SUBMODEL) {
					vm_vec_unrotate(&Mc->hit_points_all[i], &Mc->hit_points_all[i], Mc->orient);
					vm_vec_add2(&Mc->hit_points_all[i], Mc->pos);
				} else {
					if (Mc_pmi) {
						model_instance_local_to_global_point(&Mc->hit_points_all[i], &Mc->hit_points_all[i], Mc_pm, Mc_pmi, Mc->hit_submodels_all[i], Mc->orient, Mc->pos);
					}
					else {
						model_local_to_global_point(&Mc->hit_points_all[i], &Mc->hit_points_all[i], Mc_pm, Mc->hit_submodels_all[i], Mc->orient, Mc->pos);
					}
				}
			}
		}

	}

	return Mc->num_hits;
}