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{ u32 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_swap
)( void *user
, u32 ia
, u32 ib
);
56 * item_debug - draw this item quickly usually with lines
57 * cast_ray - shoot a ray against the object, if this is not set,
58 * raycasts will simply return the hit on the bvh node
61 void (*item_debug
)( void *user
, u32 item_index
);
62 int (*cast_ray
)( void *user
, u32 index
, v3f co
, v3f dir
, ray_hit
*hit
);
65 VG_STATIC
void bh_update_bounds( bh_tree
*bh
, u32 inode
)
67 bh_node
*node
= &bh
->nodes
[ inode
];
69 box_init_inf( node
->bbx
);
70 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
;
94 for( u32 t
=0; t
<node
->count
; t
++ )
96 u32 idx
= node
->start
+t
;
97 avg
+= bh
->system
->item_centroid( bh
->user
, idx
, axis
);
99 avg
/= (float)node
->count
;
104 j
= i
+ node
->count
-1;
108 if( bh
->system
->item_centroid( bh
->user
, i
, axis
) < split
)
112 bh
->system
->item_swap( bh
->user
, i
, j
);
117 u32 left_count
= i
- node
->start
;
118 if( left_count
== 0 || left_count
== node
->count
) return;
120 u32 il
= bh
->node_count
++,
121 ir
= bh
->node_count
++;
123 bh_node
*lnode
= &bh
->nodes
[il
],
124 *rnode
= &bh
->nodes
[ir
];
126 lnode
->start
= node
->start
;
127 lnode
->count
= left_count
;
129 rnode
->count
= node
->count
- left_count
;
135 bh_update_bounds( bh
, il
);
136 bh_update_bounds( bh
, ir
);
137 bh_subdivide( bh
, il
);
138 bh_subdivide( bh
, ir
);
141 VG_STATIC bh_tree
*bh_create( void *lin_alloc
, bh_system
*system
,
142 void *user
, u32 item_count
, u32 max_per_leaf
)
144 assert( max_per_leaf
> 0 );
146 if( item_count
== 0 )
148 bh_tree
*bh
= vg_linear_alloc( lin_alloc
, sizeof(bh_tree
) );
155 u32 totsize
= sizeof(bh_tree
) + sizeof(bh_node
)*(item_count
*2-1);
156 bh_tree
*bh
= vg_linear_alloc( lin_alloc
, totsize
);
159 bh
->max_per_leaf
= max_per_leaf
;
161 bh_node
*root
= &bh
->nodes
[0];
166 root
->count
= item_count
;
169 bh_update_bounds( bh
, 0 );
170 bh_subdivide( bh
, 0 );
172 totsize
= sizeof(bh_tree
) + sizeof(bh_node
) * bh
->node_count
;
173 bh
= vg_linear_resize( lin_alloc
, bh
, totsize
);
175 vg_success( "BVH done, size: %u/%u\n", bh
->node_count
, (item_count
*2-1) );
179 VG_STATIC
void bh_debug_node( bh_tree
*bh
, u32 inode
, v3f pos
, u32 colour
)
181 bh_node
*node
= &bh
->nodes
[ inode
];
183 if( (pos
[0] >= node
->bbx
[0][0] && pos
[0] <= node
->bbx
[1][0]) &&
184 (pos
[2] >= node
->bbx
[0][2] && pos
[2] <= node
->bbx
[1][2]) )
188 vg_line_boxf( node
->bbx
, colour
);
190 bh_debug_node( bh
, node
->il
, pos
, colour
);
191 bh_debug_node( bh
, node
->ir
, pos
, colour
);
195 vg_line_boxf( node
->bbx
, 0xff00ff00 );
197 if( bh
->system
->item_debug
)
199 for( u32 i
=0; i
<node
->count
; i
++ )
201 u32 idx
= node
->start
+i
;
202 bh
->system
->item_debug( bh
->user
, idx
);
209 VG_STATIC
int bh_ray( bh_tree
*bh
, v3f co
, v3f dir
, ray_hit
*hit
)
211 if( bh
->node_count
< 2 )
219 stack
[1] = bh
->nodes
[0].il
;
220 stack
[2] = bh
->nodes
[0].ir
;
224 bh_node
*inode
= &bh
->nodes
[ stack
[depth
] ];
225 if( ray_aabb( inode
->bbx
, co
, dir
, hit
->dist
) )
229 for( u32 i
=0; i
<inode
->count
; i
++ )
231 u32 idx
= inode
->start
+i
;
233 if( bh
->system
->cast_ray
)
234 count
+= bh
->system
->cast_ray( bh
->user
, idx
, co
, dir
, hit
);
243 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
;
263 VG_STATIC
int bh_select( bh_tree
*bh
, boxf box
, u32
*buffer
, int len
)
265 if( bh
->node_count
< 2 )
273 stack
[1] = bh
->nodes
[0].il
;
274 stack
[2] = bh
->nodes
[0].ir
;
278 bh_node
*inode
= &bh
->nodes
[ stack
[depth
] ];
279 if( box_overlap( inode
->bbx
, box
) )
283 if( count
+ inode
->count
>= len
)
286 for( u32 i
=0; i
<inode
->count
; i
++ )
287 buffer
[ count
++ ] = inode
->start
+i
;
293 if( depth
+1 >= vg_list_size(stack
) )
295 vg_error( "Maximum stack reached!\n" );
299 stack
[depth
] = inode
->il
;
300 stack
[depth
+1] = inode
->ir
;