X-Git-Url: https://harrygodden.com/git/?p=vg.git;a=blobdiff_plain;f=vg_bvh.h;fp=vg_bvh.h;h=85790c5d58b310f35d2a319036891123cb37706f;hp=0000000000000000000000000000000000000000;hb=fce86711735b15bff37de0f70716808410fcf269;hpb=1c305409e8eca9cf8449d681df73208956ce14df

diff --git a/vg_bvh.h b/vg_bvh.h
new file mode 100644
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--- /dev/null
+++ b/vg_bvh.h
@@ -0,0 +1,415 @@
+#pragma once
+#include "vg_mem.h"
+#include "vg_m.h"
+#include "vg_lines.h"
+
+/*
+ * Usage:
+ *
+ * create a bh_system with functions filled out for expand, centroid, and swap.
+ * optionally include item_debug and cast_ray functions if needed, otherwise,
+ *   set them to null
+ *
+ * create a bh_tree struct with:
+ *   user: a pointer back the base of the data you are ordering
+ *   system: the system we created above which will deal with the data
+ *
+ * call bh_create( bh_tree *bh, u32 item_count )
+ * static int bh_ray( bh_tree *bh, u32 inode, v3f co, v3f dir, ray_hit *hit )
+ * static int bh_select( bh_tree *bh, boxf box, u32 *buffer, int len )
+ */
+
+typedef struct bh_node bh_node;
+typedef struct bh_tree bh_tree;
+typedef struct bh_system bh_system;
+
+typedef struct ray_hit ray_hit;
+struct ray_hit{
+   float dist;
+   u32 *tri;
+   v3f pos, normal;
+};
+
+struct bh_tree{
+   u32 node_count;
+
+   bh_system *system;
+   void *user;
+   u32 max_per_leaf;
+
+   struct bh_node{
+      boxf bbx;
+
+      /* if il is 0, this is a leaf */
+      int il, count;
+      union{ int ir, start; };
+   } 
+   nodes[];
+};
+
+struct bh_system{
+   void  (*expand_bound)( void *user, boxf bound, u32 item_index );
+   float (*item_centroid)( void *user, u32 item_index, int axis );
+   void  (*item_closest)( void *user, u32 item_index, v3f point, v3f closest );
+   void  (*item_swap)( void *user, u32 ia, u32 ib );
+
+   /*
+    * Optional:
+    *   item_debug   - draw this item quickly usually with lines
+    *   cast_ray     - shoot a ray against the object, if this is not set,
+    *                  raycasts will simply return the hit on the bvh node
+    */
+
+   void  (*item_debug)( void *user, u32 item_index );
+   int   (*cast_ray)( void *user, u32 index, v3f co, v3f dir, ray_hit *hit );
+};
+
+#define BVH_FIXED_MODE
+#ifdef BVH_FIXED_MODE
+static f32 shape_bvh_centroid( void *user, u32 item_index, int axis );
+static void shape_bvh_swap( void *user, u32 ia, u32 ib );
+static void shape_bvh_expand_bound( void *user, boxf bound, u32 item_index );
+#endif
+
+static void bh_update_bounds( bh_tree *bh, u32 inode ){
+   bh_node *node = &bh->nodes[ inode ];
+
+   box_init_inf( node->bbx );
+   for( u32 i=0; i<node->count; i++ ){
+      u32 idx = node->start+i;
+#ifdef BVH_FIXED_MODE
+      shape_bvh_expand_bound( bh->user, node->bbx, idx );
+#else
+      bh->system->expand_bound( bh->user, node->bbx, idx );
+#endif
+   }
+}
+
+static void bh_subdivide( bh_tree *bh, u32 inode ){
+   bh_node *node = &bh->nodes[ inode ];
+
+   if( node->count <= bh->max_per_leaf )
+      return;
+
+   v3f extent;
+   v3_sub( node->bbx[1], node->bbx[0], extent );
+
+   int axis = 0;
+   if( extent[1] > extent[0] ) axis = 1;
+   if( extent[2] > extent[axis] ) axis = 2;
+
+   float split = node->bbx[0][axis] + extent[axis]*0.5f;
+   float avg = 0.0;
+   for( u32 t=0; t<node->count; t++ ){
+      u32 idx = node->start+t;
+#ifdef BVH_FIXED_MODE
+      avg += shape_bvh_centroid( bh->user, idx, axis );
+#else
+      avg += bh->system->item_centroid( bh->user, idx, axis );
+#endif
+   }
+   avg /= (float)node->count;
+   split = avg;
+
+
+   i32 i = node->start,
+       j = i + node->count-1;
+   
+   while( i <= j ){
+#ifdef BVH_FIXED_MODE
+      f32 centroid = shape_bvh_centroid( bh->user, i, axis );
+#else
+      f32 centroid = bh->system->item_centroid( bh->user, i, axis );
+#endif
+
+      if( centroid < split )
+         i ++;
+      else{
+#ifdef BVH_FIXED_MODE
+         shape_bvh_swap( bh->user, i, j );
+#else
+         bh->system->item_swap( bh->user, i, j );
+#endif
+         j --;
+      }
+   }
+
+   u32 left_count = i - node->start;
+   if( left_count == 0 || left_count == node->count ) return;
+
+   u32 il = bh->node_count ++,
+       ir = bh->node_count ++;
+
+   bh_node *lnode = &bh->nodes[il],
+           *rnode = &bh->nodes[ir];
+
+   lnode->start = node->start;
+   lnode->count = left_count;
+   rnode->start = i;
+   rnode->count = node->count - left_count;
+
+   node->il = il;
+   node->ir = ir;
+   node->count = 0;
+
+   bh_update_bounds( bh, il );
+   bh_update_bounds( bh, ir );
+   bh_subdivide( bh, il );
+   bh_subdivide( bh, ir );
+}
+
+static void bh_rebuild( bh_tree *bh, u32 item_count ){
+   bh_node *root = &bh->nodes[0];
+   bh->node_count = 1;
+   
+   root->il = 0;
+   root->ir = 0;
+   root->count = item_count;
+   root->start = 0;
+
+   bh_update_bounds( bh, 0 );
+
+   if( item_count > 2 )
+      bh_subdivide( bh, 0 );
+}
+
+static bh_tree *bh_create( void *lin_alloc, bh_system *system, 
+                              void *user, u32 item_count, u32 max_per_leaf ){
+   assert( max_per_leaf > 0 );
+
+   u32 alloc_count = VG_MAX( 1, item_count );
+
+   u32 totsize = sizeof(bh_tree) + sizeof(bh_node)*(alloc_count*2-1);
+   bh_tree *bh = lin_alloc? vg_linear_alloc( lin_alloc, vg_align8(totsize) ):
+                            malloc( totsize );
+   bh->system = system;
+   bh->user = user;
+   bh->max_per_leaf = max_per_leaf;
+   bh_rebuild( bh, item_count );
+
+   if( lin_alloc ){
+      totsize = vg_align8(sizeof(bh_tree) + sizeof(bh_node) * bh->node_count);
+      bh = vg_linear_resize( lin_alloc, bh, totsize );
+   }
+
+   vg_success( "BVH done, size: %u/%u\n", bh->node_count, (alloc_count*2-1) );
+   return bh;
+}
+
+/*
+ * Draw items in this leaf node.
+ * *item_debug() must be set!
+ */
+static void bh_debug_leaf( bh_tree *bh, bh_node *node ){
+   vg_line_boxf( node->bbx, 0xff00ff00 );
+
+   if( bh->system->item_debug ){
+      for( u32 i=0; i<node->count; i++ ){
+         u32 idx = node->start+i;
+         bh->system->item_debug( bh->user, idx );
+      }
+   }
+}
+
+/*
+ * Trace the bh tree all the way down to the leaf nodes where pos is inside
+ */
+static void bh_debug_trace( bh_tree *bh, u32 inode, v3f pos, u32 colour ){
+   bh_node *node = &bh->nodes[ inode ];
+
+   if( (pos[0] >= node->bbx[0][0] && pos[0] <= node->bbx[1][0]) &&
+       (pos[2] >= node->bbx[0][2] && pos[2] <= node->bbx[1][2]) )
+   {
+      if( !node->count ){
+         vg_line_boxf( node->bbx, colour );
+
+         bh_debug_trace( bh, node->il, pos, colour );
+         bh_debug_trace( bh, node->ir, pos, colour );
+      }
+      else{
+         if( bh->system->item_debug )
+            bh_debug_leaf( bh, node );
+      }
+   }
+}
+
+typedef struct bh_iter bh_iter;
+struct bh_iter{
+   struct {
+      i32 id, depth;
+   }
+   stack[64];
+
+   enum bh_query_type{
+      k_bh_query_box,
+      k_bh_query_ray,
+      k_bh_query_range
+   }
+   query;
+
+   union{
+      struct{
+         boxf box;
+      }
+      box;
+
+      struct{
+         v3f co, inv_dir;
+         f32 max_dist;
+      }
+      ray;
+
+      struct {
+         v3f co;
+         f32 dist_sqr;
+      }
+      range;
+   };
+
+   i32 depth, i;
+};
+
+static void bh_iter_init_generic( i32 root, bh_iter *it ){
+   it->stack[0].id = root;
+   it->stack[0].depth = 0;
+   it->depth = 0;
+   it->i = 0;
+}
+
+static void bh_iter_init_box( i32 root, bh_iter *it, boxf box ){
+   bh_iter_init_generic( root, it );
+   it->query = k_bh_query_box;
+
+   box_copy( box, it->box.box );
+}
+
+static void bh_iter_init_ray( i32 root, bh_iter *it, v3f co, 
+                                 v3f dir, f32 max_dist ){
+   bh_iter_init_generic( root, it );
+   it->query = k_bh_query_ray;
+   
+   v3_div( (v3f){1.0f,1.0f,1.0f}, dir, it->ray.inv_dir );
+   v3_copy( co, it->ray.co );
+   it->ray.max_dist = max_dist;
+}
+
+static void bh_iter_init_range( i32 root, bh_iter *it, v3f co, f32 range ){
+   bh_iter_init_generic( root, it );
+   it->query = k_bh_query_range;
+
+   v3_copy( co, it->range.co );
+   it->range.dist_sqr = range*range;
+}
+
+/* NOTE: does not compute anything beyond the leaf level. element level tests
+ *       should be implemented by the users code.
+ *
+ *       this is like a 'broad phase only' deal.
+ */
+static i32 bh_next( bh_tree *bh, bh_iter *it, i32 *em ){
+   while( it->depth >= 0 ){
+      bh_node *inode = &bh->nodes[ it->stack[it->depth].id ];
+      
+      /* Only process overlapping nodes */
+      i32 q = 0;
+
+      if( it->i ) /* already checked */
+         q = 1;
+      else{
+         if( it->query == k_bh_query_box )
+            q = box_overlap( inode->bbx, it->box.box );
+         else if( it->query == k_bh_query_ray )
+            q = ray_aabb1( inode->bbx, it->ray.co, 
+                           it->ray.inv_dir, it->ray.max_dist );
+         else {
+            v3f nearest;
+            closest_point_aabb( it->range.co, inode->bbx, nearest );
+
+            if( v3_dist2( nearest, it->range.co ) <= it->range.dist_sqr )
+               q = 1;
+         }
+      }
+
+      if( !q ){
+         it->depth --;
+         continue;
+      }
+
+      if( inode->count ){
+         if( it->i < inode->count ){
+            *em = inode->start+it->i;
+            it->i ++;
+            return 1;
+         }
+         else{
+            it->depth --;
+            it->i = 0;
+         }
+      }
+      else{
+         if( it->depth+1 >= vg_list_size(it->stack) ){
+            vg_error( "Maximum stack reached!\n" );
+            return 0;
+         }
+
+         it->stack[it->depth  ].id = inode->il;
+         it->stack[it->depth+1].id = inode->ir;
+         it->depth ++;
+         it->i = 0;
+      }
+   }
+
+   return 0;
+}
+
+static int bh_closest_point( bh_tree *bh, v3f pos, 
+                                v3f closest, float max_dist )
+{
+   if( bh->node_count < 2 )
+      return -1;
+
+   max_dist = max_dist*max_dist;
+
+   int queue[ 128 ],
+       depth = 0,
+       best_item = -1;
+
+   queue[0] = 0;
+
+   while( depth >= 0 ){
+      bh_node *inode = &bh->nodes[ queue[depth] ];
+
+      v3f p1;
+      closest_point_aabb( pos, inode->bbx, p1 );
+
+      /* branch into node if its closer than current best */
+      float node_dist = v3_dist2( pos, p1 );
+      if( node_dist < max_dist ){
+         if( inode->count ){
+            for( int i=0; i<inode->count; i++ ){
+               v3f p2;
+               bh->system->item_closest( bh->user, inode->start+i, pos, p2 );
+
+               float item_dist = v3_dist2( pos, p2 );
+               if( item_dist < max_dist ){
+                  max_dist = item_dist;
+                  v3_copy( p2, closest );
+                  best_item = inode->start+i;
+               }
+            }
+
+            depth --;
+         }
+         else{
+            queue[depth] = inode->il;
+            queue[depth+1] = inode->ir;
+
+            depth ++;
+         }
+      }
+      else
+         depth --;
+   }
+
+   return best_item;
+}