2 * Copyright (C) 2021-2022 Mt.ZERO Software, Harry Godden - All Rights Reserved
10 #include "vg/vg_lines.h"
15 * create a bh_system with functions filled out for expand, centroid, and swap.
16 * optionally include item_debug and cast_ray functions if needed, otherwise,
19 * create a bh_tree struct with:
20 * user: a pointer back the base of the data you are ordering
21 * system: the system we created above which will deal with the data
23 * call bh_create( bh_tree *bh, u32 item_count )
24 * VG_STATIC int bh_ray( bh_tree *bh, u32 inode, v3f co, v3f dir, ray_hit *hit )
25 * VG_STATIC int bh_select( bh_tree *bh, boxf box, u32 *buffer, int len )
28 typedef struct bh_node bh_node
;
29 typedef struct bh_tree bh_tree
;
30 typedef struct bh_system bh_system
;
32 typedef struct ray_hit ray_hit
;
50 /* if il is 0, this is a leaf */
52 union{ int ir
, start
; };
58 void (*expand_bound
)( void *user
, boxf bound
, u32 item_index
);
59 float (*item_centroid
)( void *user
, u32 item_index
, int axis
);
60 void (*item_closest
)( void *user
, u32 item_index
, v3f point
, v3f closest
);
61 void (*item_swap
)( void *user
, u32 ia
, u32 ib
);
65 * item_debug - draw this item quickly usually with lines
66 * cast_ray - shoot a ray against the object, if this is not set,
67 * raycasts will simply return the hit on the bvh node
70 void (*item_debug
)( void *user
, u32 item_index
);
71 int (*cast_ray
)( void *user
, u32 index
, v3f co
, v3f dir
, ray_hit
*hit
);
74 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
){
85 bh_node
*node
= &bh
->nodes
[ inode
];
87 if( node
->count
<= bh
->max_per_leaf
)
91 v3_sub( node
->bbx
[1], node
->bbx
[0], extent
);
94 if( extent
[1] > extent
[0] ) axis
= 1;
95 if( extent
[2] > extent
[axis
] ) axis
= 2;
97 float split
= node
->bbx
[0][axis
] + extent
[axis
]*0.5f
;
99 for( u32 t
=0; t
<node
->count
; t
++ )
101 u32 idx
= node
->start
+t
;
102 avg
+= bh
->system
->item_centroid( bh
->user
, idx
, axis
);
104 avg
/= (float)node
->count
;
109 j
= i
+ node
->count
-1;
112 if( bh
->system
->item_centroid( bh
->user
, i
, axis
) < split
)
115 bh
->system
->item_swap( bh
->user
, i
, j
);
120 u32 left_count
= i
- node
->start
;
121 if( left_count
== 0 || left_count
== node
->count
) return;
123 u32 il
= bh
->node_count
++,
124 ir
= bh
->node_count
++;
126 bh_node
*lnode
= &bh
->nodes
[il
],
127 *rnode
= &bh
->nodes
[ir
];
129 lnode
->start
= node
->start
;
130 lnode
->count
= left_count
;
132 rnode
->count
= node
->count
- left_count
;
138 bh_update_bounds( bh
, il
);
139 bh_update_bounds( bh
, ir
);
140 bh_subdivide( bh
, il
);
141 bh_subdivide( bh
, ir
);
144 VG_STATIC bh_tree
*bh_create( void *lin_alloc
, bh_system
*system
,
145 void *user
, u32 item_count
, u32 max_per_leaf
){
146 assert( max_per_leaf
> 0 );
148 u32 alloc_count
= VG_MAX( 1, item_count
);
150 u32 totsize
= sizeof(bh_tree
) + sizeof(bh_node
)*(alloc_count
*2-1);
151 bh_tree
*bh
= vg_linear_alloc( lin_alloc
, vg_align8(totsize
) );
154 bh
->max_per_leaf
= max_per_leaf
;
156 bh_node
*root
= &bh
->nodes
[0];
161 root
->count
= item_count
;
164 bh_update_bounds( bh
, 0 );
167 bh_subdivide( bh
, 0 );
169 totsize
= vg_align8(sizeof(bh_tree
) + sizeof(bh_node
) * bh
->node_count
);
170 bh
= vg_linear_resize( lin_alloc
, bh
, totsize
);
172 vg_success( "BVH done, size: %u/%u\n", bh
->node_count
, (alloc_count
*2-1) );
177 * Draw items in this leaf node.
178 * *item_debug() must be set!
180 VG_STATIC
void bh_debug_leaf( bh_tree
*bh
, bh_node
*node
){
181 vg_line_boxf( node
->bbx
, 0xff00ff00 );
183 if( bh
->system
->item_debug
){
184 for( u32 i
=0; i
<node
->count
; i
++ ){
185 u32 idx
= node
->start
+i
;
186 bh
->system
->item_debug( bh
->user
, idx
);
192 * Trace the bh tree all the way down to the leaf nodes where pos is inside
194 VG_STATIC
void bh_debug_trace( bh_tree
*bh
, u32 inode
, v3f pos
, u32 colour
){
195 bh_node
*node
= &bh
->nodes
[ inode
];
197 if( (pos
[0] >= node
->bbx
[0][0] && pos
[0] <= node
->bbx
[1][0]) &&
198 (pos
[2] >= node
->bbx
[0][2] && pos
[2] <= node
->bbx
[1][2]) )
201 vg_line_boxf( node
->bbx
, colour
);
203 bh_debug_trace( bh
, node
->il
, pos
, colour
);
204 bh_debug_trace( bh
, node
->ir
, pos
, colour
);
207 if( bh
->system
->item_debug
)
208 bh_debug_leaf( bh
, node
);
213 VG_STATIC
int bh_ray( bh_tree
*bh
, v3f co
, v3f dir
, ray_hit
*hit
){
214 if( bh
->node_count
< 2 )
222 stack
[1] = bh
->nodes
[0].il
;
223 stack
[2] = bh
->nodes
[0].ir
;
226 v3_div( (v3f
){1.0f
,1.0f
,1.0f
}, dir
, dir_inv
);
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
;
291 VG_STATIC
void bh_iter_init_box( i32 root
, bh_iter
*it
, boxf box
){
292 it
->query
= k_bh_query_box
;
293 it
->stack
[0].id
= root
;
294 it
->stack
[0].depth
= 0;
298 box_copy( box
, it
->box
.box
);
301 VG_STATIC
void bh_iter_init_ray( i32 root
, bh_iter
*it
, v3f co
,
302 v3f dir
, f32 max_dist
){
303 it
->query
= k_bh_query_ray
;
304 it
->stack
[0].id
= root
;
305 it
->stack
[0].depth
= 0;
309 v3_div( (v3f
){1.0f
,1.0f
,1.0f
}, dir
, it
->ray
.inv_dir
);
310 v3_copy( co
, it
->ray
.co
);
311 it
->ray
.max_dist
= max_dist
;
314 VG_STATIC i32
bh_next( bh_tree
*bh
, bh_iter
*it
, i32
*em
){
315 while( it
->depth
>= 0 ){
316 bh_node
*inode
= &bh
->nodes
[ it
->stack
[it
->depth
].id
];
318 /* Only process overlapping nodes */
321 if( it
->query
== k_bh_query_box
)
322 q
= box_overlap( inode
->bbx
, it
->box
.box
);
324 q
= ray_aabb1( inode
->bbx
, it
->ray
.co
,
325 it
->ray
.inv_dir
, it
->ray
.max_dist
);
333 if( it
->i
< inode
->count
){
334 *em
= inode
->start
+it
->i
;
344 if( it
->depth
+1 >= vg_list_size(it
->stack
) ){
345 vg_error( "Maximum stack reached!\n" );
349 it
->stack
[it
->depth
].id
= inode
->il
;
350 it
->stack
[it
->depth
+1].id
= inode
->ir
;
359 VG_STATIC
int bh_closest_point( bh_tree
*bh
, v3f pos
,
360 v3f closest
, float max_dist
)
362 if( bh
->node_count
< 2 )
365 max_dist
= max_dist
*max_dist
;
374 bh_node
*inode
= &bh
->nodes
[ queue
[depth
] ];
377 closest_point_aabb( pos
, inode
->bbx
, p1
);
379 /* branch into node if its closer than current best */
380 float node_dist
= v3_dist2( pos
, p1
);
381 if( node_dist
< max_dist
){
383 for( int i
=0; i
<inode
->count
; i
++ ){
385 bh
->system
->item_closest( bh
->user
, inode
->start
+i
, pos
, p2
);
387 float item_dist
= v3_dist2( pos
, p2
);
388 if( item_dist
< max_dist
){
389 max_dist
= item_dist
;
390 v3_copy( p2
, closest
);
391 best_item
= inode
->start
+i
;
398 queue
[depth
] = inode
->il
;
399 queue
[depth
+1] = inode
->ir
;