95 lines
2.5 KiB
Rust
95 lines
2.5 KiB
Rust
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use crate::aabb::Aabb;
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//da algaritum
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//lista boxens
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//sort by {minx,maxx,miny,maxy,minz,maxz} (6 lists)
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//find the sets that minimizes the sum of surface areas
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//splitting is done when the minimum split sum of surface areas is larger than the node's own surface area
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//start with bisection into octrees because a bad bvh is still 1000x better than no bvh
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//sort the centerpoints on each axis (3 lists)
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//bv is put into octant based on whether it is upper or lower in each list
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pub struct BvhNode{
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children:Vec<Self>,
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models:Vec<u32>,
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aabb:Aabb,
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}
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pub fn generate_bvh(boxen:Vec<Aabb>)->BvhNode{
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generate_bvh_node(boxen.into_iter().enumerate().collect())
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}
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fn generate_bvh_node(boxen:Vec<(usize,Aabb)>)->BvhNode{
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let n=boxen.len();
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if n<20{
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let mut aabb=Aabb::new();
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let models=boxen.into_iter().map(|b|{aabb.join(&b.1);b.0 as u32}).collect();
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BvhNode{
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children:Vec::new(),
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models,
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aabb,
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}
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}else{
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let mut octant=std::collections::HashMap::with_capacity(n);//this ids which octant the boxen is put in
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let mut sort_x=Vec::with_capacity(n);
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let mut sort_y=Vec::with_capacity(n);
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let mut sort_z=Vec::with_capacity(n);
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for (i,aabb) in boxen.iter(){
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let center=aabb.center();
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octant.insert(*i,0);
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sort_x.push((*i,center.x));
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sort_y.push((*i,center.y));
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sort_z.push((*i,center.z));
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}
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sort_x.sort_by(|tup0,tup1|tup0.1.partial_cmp(&tup1.1).unwrap());
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sort_y.sort_by(|tup0,tup1|tup0.1.partial_cmp(&tup1.1).unwrap());
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sort_z.sort_by(|tup0,tup1|tup0.1.partial_cmp(&tup1.1).unwrap());
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let h=n/2;
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let median_x=sort_x[h].1;
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let median_y=sort_y[h].1;
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let median_z=sort_z[h].1;
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for (i,c) in sort_x{
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if median_x<c{
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octant.insert(i,octant[&i]+1<<0);
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}
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}
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for (i,c) in sort_y{
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if median_y<c{
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octant.insert(i,octant[&i]+1<<1);
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}
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}
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for (i,c) in sort_z{
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if median_z<c{
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octant.insert(i,octant[&i]+1<<2);
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}
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}
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//generate lists for unique octant values
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let mut list_list=Vec::with_capacity(8);
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let mut octant_list=Vec::with_capacity(8);
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for (i,aabb) in boxen.into_iter(){
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let octant_id=octant[&i];
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let list_id=if let Some(list_id)=octant_list.iter().position(|&id|id==octant_id){
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list_id
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}else{
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let list_id=list_list.len();
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octant_list.push(octant_id);
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list_list.push(Vec::new());
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list_id
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};
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list_list[list_id].push((i,aabb));
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}
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let mut aabb=Aabb::new();
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let children=list_list.into_iter().map(|b|{
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let node=generate_bvh_node(b);
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aabb.join(&node.aabb);
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node
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}).collect();
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BvhNode{
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children,
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models:Vec::new(),
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aabb,
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}
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}
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}
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