2 * Copyright (C) 2021-2022 Mt.ZERO Software, Harry Godden - All Rights Reserved
12 * create a bh_system with functions filled out for expand, centroid, and swap.
13 * optionally include item_debug and cast_ray functions if needed, otherwise,
16 * create a bh_tree struct with:
17 * user: a pointer back the base of the data you are ordering
18 * system: the system we created above which will deal with the data
20 * call bh_create( bh_tree *bh, u32 item_count )
21 * VG_STATIC int bh_ray( bh_tree *bh, u32 inode, v3f co, v3f dir, ray_hit *hit )
22 * VG_STATIC int bh_select( bh_tree *bh, boxf box, u32 *buffer, int len )
25 typedef struct bh_node bh_node
;
26 typedef struct bh_tree bh_tree
;
27 typedef struct bh_system bh_system
;
41 /* if il is 0, this is a leaf */
43 union{ int ir
, start
; };
50 void (*expand_bound
)( void *user
, boxf bound
, u32 item_index
);
51 float (*item_centroid
)( void *user
, u32 item_index
, int axis
);
52 void (*item_closest
)( void *user
, u32 item_index
, v3f point
, v3f closest
);
53 void (*item_swap
)( void *user
, u32 ia
, u32 ib
);
57 * item_debug - draw this item quickly usually with lines
58 * cast_ray - shoot a ray against the object, if this is not set,
59 * raycasts will simply return the hit on the bvh node
62 void (*item_debug
)( void *user
, u32 item_index
);
63 int (*cast_ray
)( void *user
, u32 index
, v3f co
, v3f dir
, ray_hit
*hit
);
66 VG_STATIC
void bh_update_bounds( bh_tree
*bh
, u32 inode
)
68 bh_node
*node
= &bh
->nodes
[ inode
];
70 box_init_inf( node
->bbx
);
71 for( u32 i
=0; i
<node
->count
; i
++ ){
72 u32 idx
= node
->start
+i
;
73 bh
->system
->expand_bound( bh
->user
, node
->bbx
, idx
);
77 VG_STATIC
void bh_subdivide( bh_tree
*bh
, u32 inode
)
79 bh_node
*node
= &bh
->nodes
[ inode
];
81 if( node
->count
<= bh
->max_per_leaf
)
85 v3_sub( node
->bbx
[1], node
->bbx
[0], extent
);
88 if( extent
[1] > extent
[0] ) axis
= 1;
89 if( extent
[2] > extent
[axis
] ) axis
= 2;
91 float split
= node
->bbx
[0][axis
] + extent
[axis
]*0.5f
;
93 for( u32 t
=0; t
<node
->count
; t
++ )
95 u32 idx
= node
->start
+t
;
96 avg
+= bh
->system
->item_centroid( bh
->user
, idx
, axis
);
98 avg
/= (float)node
->count
;
103 j
= i
+ node
->count
-1;
106 if( bh
->system
->item_centroid( bh
->user
, i
, axis
) < split
)
109 bh
->system
->item_swap( bh
->user
, i
, j
);
114 u32 left_count
= i
- node
->start
;
115 if( left_count
== 0 || left_count
== node
->count
) return;
117 u32 il
= bh
->node_count
++,
118 ir
= bh
->node_count
++;
120 bh_node
*lnode
= &bh
->nodes
[il
],
121 *rnode
= &bh
->nodes
[ir
];
123 lnode
->start
= node
->start
;
124 lnode
->count
= left_count
;
126 rnode
->count
= node
->count
- left_count
;
132 bh_update_bounds( bh
, il
);
133 bh_update_bounds( bh
, ir
);
134 bh_subdivide( bh
, il
);
135 bh_subdivide( bh
, ir
);
138 VG_STATIC bh_tree
*bh_create( void *lin_alloc
, bh_system
*system
,
139 void *user
, u32 item_count
, u32 max_per_leaf
)
141 assert( max_per_leaf
> 0 );
143 u32 alloc_count
= VG_MAX( 1, item_count
);
145 u32 totsize
= sizeof(bh_tree
) + sizeof(bh_node
)*(alloc_count
*2-1);
146 bh_tree
*bh
= vg_linear_alloc( lin_alloc
, vg_align8(totsize
) );
149 bh
->max_per_leaf
= max_per_leaf
;
151 bh_node
*root
= &bh
->nodes
[0];
156 root
->count
= item_count
;
159 bh_update_bounds( bh
, 0 );
162 bh_subdivide( bh
, 0 );
164 totsize
= vg_align8(sizeof(bh_tree
) + sizeof(bh_node
) * bh
->node_count
);
165 bh
= vg_linear_resize( lin_alloc
, bh
, totsize
);
167 vg_success( "BVH done, size: %u/%u\n", bh
->node_count
, (alloc_count
*2-1) );
172 * Draw items in this leaf node.
173 * *item_debug() must be set!
175 VG_STATIC
void bh_debug_leaf( bh_tree
*bh
, bh_node
*node
)
177 vg_line_boxf( node
->bbx
, 0xff00ff00 );
179 if( bh
->system
->item_debug
){
180 for( u32 i
=0; i
<node
->count
; i
++ ){
181 u32 idx
= node
->start
+i
;
182 bh
->system
->item_debug( bh
->user
, idx
);
188 * Trace the bh tree all the way down to the leaf nodes where pos is inside
190 VG_STATIC
void bh_debug_trace( bh_tree
*bh
, u32 inode
, v3f pos
, u32 colour
)
192 bh_node
*node
= &bh
->nodes
[ inode
];
194 if( (pos
[0] >= node
->bbx
[0][0] && pos
[0] <= node
->bbx
[1][0]) &&
195 (pos
[2] >= node
->bbx
[0][2] && pos
[2] <= node
->bbx
[1][2]) )
198 vg_line_boxf( node
->bbx
, colour
);
200 bh_debug_trace( bh
, node
->il
, pos
, colour
);
201 bh_debug_trace( bh
, node
->ir
, pos
, colour
);
204 if( bh
->system
->item_debug
)
205 bh_debug_leaf( bh
, node
);
210 VG_STATIC
int bh_ray( bh_tree
*bh
, v3f co
, v3f dir
, ray_hit
*hit
)
212 if( bh
->node_count
< 2 )
220 stack
[1] = bh
->nodes
[0].il
;
221 stack
[2] = bh
->nodes
[0].ir
;
224 dir_inv
[0] = 1.0f
/dir
[0];
225 dir_inv
[1] = 1.0f
/dir
[1];
226 dir_inv
[2] = 1.0f
/dir
[2];
229 bh_node
*inode
= &bh
->nodes
[ stack
[depth
] ];
230 if( ray_aabb1( inode
->bbx
, co
, dir_inv
, hit
->dist
) ){
232 for( u32 i
=0; i
<inode
->count
; i
++ ){
233 u32 idx
= inode
->start
+i
;
235 if( bh
->system
->cast_ray
)
236 count
+= bh
->system
->cast_ray( bh
->user
, idx
, co
, dir
, hit
);
244 if( depth
+1 >= vg_list_size(stack
) ){
245 vg_error( "Maximum stack reached!\n" );
249 stack
[depth
] = inode
->il
;
250 stack
[depth
+1] = inode
->ir
;
262 typedef struct bh_iter bh_iter
;
274 VG_STATIC
void bh_iter_init( int root
, bh_iter
*it
)
276 it
->stack
[0].id
= root
;
277 it
->stack
[0].depth
= 0;
282 VG_STATIC
int bh_next( bh_tree
*bh
, bh_iter
*it
, boxf box
, int *em
)
284 while( it
->depth
>= 0 ){
285 bh_node
*inode
= &bh
->nodes
[ it
->stack
[it
->depth
].id
];
287 /* Only process overlapping nodes */
288 if( !box_overlap( inode
->bbx
, box
) ){
294 if( it
->i
< inode
->count
){
295 *em
= inode
->start
+it
->i
;
305 if( it
->depth
+1 >= vg_list_size(it
->stack
) ){
306 vg_error( "Maximum stack reached!\n" );
310 it
->stack
[it
->depth
].id
= inode
->il
;
311 it
->stack
[it
->depth
+1].id
= inode
->ir
;
320 VG_STATIC
int bh_closest_point( bh_tree
*bh
, v3f pos
,
321 v3f closest
, float max_dist
)
323 if( bh
->node_count
< 2 )
326 max_dist
= max_dist
*max_dist
;
335 bh_node
*inode
= &bh
->nodes
[ queue
[depth
] ];
338 closest_point_aabb( pos
, inode
->bbx
, p1
);
340 /* branch into node if its closer than current best */
341 float node_dist
= v3_dist2( pos
, p1
);
342 if( node_dist
< max_dist
){
344 for( int i
=0; i
<inode
->count
; i
++ ){
346 bh
->system
->item_closest( bh
->user
, inode
->start
+i
, pos
, p2
);
348 float item_dist
= v3_dist2( pos
, p2
);
349 if( item_dist
< max_dist
){
350 max_dist
= item_dist
;
351 v3_copy( p2
, closest
);
352 best_item
= inode
->start
+i
;
359 queue
[depth
] = inode
->il
;
360 queue
[depth
+1] = inode
->ir
;