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
;
29 typedef struct ray_hit ray_hit
;
48 /* if il is 0, this is a leaf */
50 union{ int ir
, start
; };
57 void (*expand_bound
)( void *user
, boxf bound
, u32 item_index
);
58 float (*item_centroid
)( void *user
, u32 item_index
, int axis
);
59 void (*item_closest
)( void *user
, u32 item_index
, v3f point
, v3f closest
);
60 void (*item_swap
)( void *user
, u32 ia
, u32 ib
);
64 * item_debug - draw this item quickly usually with lines
65 * cast_ray - shoot a ray against the object, if this is not set,
66 * raycasts will simply return the hit on the bvh node
69 void (*item_debug
)( void *user
, u32 item_index
);
70 int (*cast_ray
)( void *user
, u32 index
, v3f co
, v3f dir
, ray_hit
*hit
);
73 VG_STATIC
void bh_update_bounds( bh_tree
*bh
, u32 inode
)
75 bh_node
*node
= &bh
->nodes
[ inode
];
77 box_init_inf( node
->bbx
);
78 for( u32 i
=0; i
<node
->count
; i
++ ){
79 u32 idx
= node
->start
+i
;
80 bh
->system
->expand_bound( bh
->user
, node
->bbx
, idx
);
84 VG_STATIC
void bh_subdivide( bh_tree
*bh
, u32 inode
)
86 bh_node
*node
= &bh
->nodes
[ inode
];
88 if( node
->count
<= bh
->max_per_leaf
)
92 v3_sub( node
->bbx
[1], node
->bbx
[0], extent
);
95 if( extent
[1] > extent
[0] ) axis
= 1;
96 if( extent
[2] > extent
[axis
] ) axis
= 2;
98 float split
= node
->bbx
[0][axis
] + extent
[axis
]*0.5f
;
100 for( u32 t
=0; t
<node
->count
; t
++ )
102 u32 idx
= node
->start
+t
;
103 avg
+= bh
->system
->item_centroid( bh
->user
, idx
, axis
);
105 avg
/= (float)node
->count
;
110 j
= i
+ node
->count
-1;
113 if( bh
->system
->item_centroid( bh
->user
, i
, axis
) < split
)
116 bh
->system
->item_swap( bh
->user
, i
, j
);
121 u32 left_count
= i
- node
->start
;
122 if( left_count
== 0 || left_count
== node
->count
) return;
124 u32 il
= bh
->node_count
++,
125 ir
= bh
->node_count
++;
127 bh_node
*lnode
= &bh
->nodes
[il
],
128 *rnode
= &bh
->nodes
[ir
];
130 lnode
->start
= node
->start
;
131 lnode
->count
= left_count
;
133 rnode
->count
= node
->count
- left_count
;
139 bh_update_bounds( bh
, il
);
140 bh_update_bounds( bh
, ir
);
141 bh_subdivide( bh
, il
);
142 bh_subdivide( bh
, ir
);
145 VG_STATIC bh_tree
*bh_create( void *lin_alloc
, bh_system
*system
,
146 void *user
, u32 item_count
, u32 max_per_leaf
)
148 assert( max_per_leaf
> 0 );
150 u32 alloc_count
= VG_MAX( 1, item_count
);
152 u32 totsize
= sizeof(bh_tree
) + sizeof(bh_node
)*(alloc_count
*2-1);
153 bh_tree
*bh
= vg_linear_alloc( lin_alloc
, vg_align8(totsize
) );
156 bh
->max_per_leaf
= max_per_leaf
;
158 bh_node
*root
= &bh
->nodes
[0];
163 root
->count
= item_count
;
166 bh_update_bounds( bh
, 0 );
169 bh_subdivide( bh
, 0 );
171 totsize
= vg_align8(sizeof(bh_tree
) + sizeof(bh_node
) * bh
->node_count
);
172 bh
= vg_linear_resize( lin_alloc
, bh
, totsize
);
174 vg_success( "BVH done, size: %u/%u\n", bh
->node_count
, (alloc_count
*2-1) );
179 * Draw items in this leaf node.
180 * *item_debug() must be set!
182 VG_STATIC
void bh_debug_leaf( bh_tree
*bh
, bh_node
*node
)
184 vg_line_boxf( node
->bbx
, 0xff00ff00 );
186 if( bh
->system
->item_debug
){
187 for( u32 i
=0; i
<node
->count
; i
++ ){
188 u32 idx
= node
->start
+i
;
189 bh
->system
->item_debug( bh
->user
, idx
);
195 * Trace the bh tree all the way down to the leaf nodes where pos is inside
197 VG_STATIC
void bh_debug_trace( bh_tree
*bh
, u32 inode
, v3f pos
, u32 colour
)
199 bh_node
*node
= &bh
->nodes
[ inode
];
201 if( (pos
[0] >= node
->bbx
[0][0] && pos
[0] <= node
->bbx
[1][0]) &&
202 (pos
[2] >= node
->bbx
[0][2] && pos
[2] <= node
->bbx
[1][2]) )
205 vg_line_boxf( node
->bbx
, colour
);
207 bh_debug_trace( bh
, node
->il
, pos
, colour
);
208 bh_debug_trace( bh
, node
->ir
, pos
, colour
);
211 if( bh
->system
->item_debug
)
212 bh_debug_leaf( bh
, node
);
217 VG_STATIC
int bh_ray( bh_tree
*bh
, v3f co
, v3f dir
, ray_hit
*hit
)
219 if( bh
->node_count
< 2 )
227 stack
[1] = bh
->nodes
[0].il
;
228 stack
[2] = bh
->nodes
[0].ir
;
231 v3_div( (v3f
){1.0f
,1.0f
,1.0f
}, dir
, dir_inv
);
234 bh_node
*inode
= &bh
->nodes
[ stack
[depth
] ];
235 if( ray_aabb1( inode
->bbx
, co
, dir_inv
, hit
->dist
) ){
237 for( u32 i
=0; i
<inode
->count
; i
++ ){
238 u32 idx
= inode
->start
+i
;
240 if( bh
->system
->cast_ray
)
241 count
+= bh
->system
->cast_ray( bh
->user
, idx
, co
, dir
, hit
);
249 if( depth
+1 >= vg_list_size(stack
) ){
250 vg_error( "Maximum stack reached!\n" );
254 stack
[depth
] = inode
->il
;
255 stack
[depth
+1] = inode
->ir
;
267 typedef struct bh_iter bh_iter
;
297 VG_STATIC
void bh_iter_init_box( i32 root
, bh_iter
*it
, boxf box
)
299 it
->query
= k_bh_query_box
;
300 it
->stack
[0].id
= root
;
301 it
->stack
[0].depth
= 0;
305 box_copy( box
, it
->box
.box
);
308 VG_STATIC
void bh_iter_init_ray( i32 root
, bh_iter
*it
, v3f co
,
309 v3f dir
, f32 max_dist
)
311 it
->query
= k_bh_query_ray
;
312 it
->stack
[0].id
= root
;
313 it
->stack
[0].depth
= 0;
317 v3_div( (v3f
){1.0f
,1.0f
,1.0f
}, dir
, it
->ray
.inv_dir
);
318 v3_copy( co
, it
->ray
.co
);
319 it
->ray
.max_dist
= max_dist
;
322 VG_STATIC i32
bh_next( bh_tree
*bh
, bh_iter
*it
, i32
*em
)
324 while( it
->depth
>= 0 ){
325 bh_node
*inode
= &bh
->nodes
[ it
->stack
[it
->depth
].id
];
327 /* Only process overlapping nodes */
330 if( it
->query
== k_bh_query_box
)
331 q
= box_overlap( inode
->bbx
, it
->box
.box
);
333 q
= ray_aabb1( inode
->bbx
, it
->ray
.co
,
334 it
->ray
.inv_dir
, it
->ray
.max_dist
);
342 if( it
->i
< inode
->count
){
343 *em
= inode
->start
+it
->i
;
353 if( it
->depth
+1 >= vg_list_size(it
->stack
) ){
354 vg_error( "Maximum stack reached!\n" );
358 it
->stack
[it
->depth
].id
= inode
->il
;
359 it
->stack
[it
->depth
+1].id
= inode
->ir
;
368 VG_STATIC
int bh_closest_point( bh_tree
*bh
, v3f pos
,
369 v3f closest
, float max_dist
)
371 if( bh
->node_count
< 2 )
374 max_dist
= max_dist
*max_dist
;
383 bh_node
*inode
= &bh
->nodes
[ queue
[depth
] ];
386 closest_point_aabb( pos
, inode
->bbx
, p1
);
388 /* branch into node if its closer than current best */
389 float node_dist
= v3_dist2( pos
, p1
);
390 if( node_dist
< max_dist
){
392 for( int i
=0; i
<inode
->count
; i
++ ){
394 bh
->system
->item_closest( bh
->user
, inode
->start
+i
, pos
, p2
);
396 float item_dist
= v3_dist2( pos
, p2
);
397 if( item_dist
< max_dist
){
398 max_dist
= item_dist
;
399 v3_copy( p2
, closest
);
400 best_item
= inode
->start
+i
;
407 queue
[depth
] = inode
->il
;
408 queue
[depth
+1] = inode
->ir
;