Implemented a SIMD version of the BVH4.
It does indeed appear to be faster with this style of traversal!
This commit is contained in:
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aed0f2ede1
387
src/accel/bvh4_simd.rs
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387
src/accel/bvh4_simd.rs
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//! This BVH4 implementation pulls a lot of ideas from the paper
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//! "Efficient Ray Tracing Kernels for Modern CPU Architectures"
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//! by Fuetterling et al.
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//!
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//! Specifically, the table-based traversal order approach they
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//! propose is largely followed by this implementation.
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#![allow(dead_code)]
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use mem_arena::MemArena;
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use crate::{
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bbox::BBox,
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bbox4::BBox4,
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boundable::Boundable,
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lerp::lerp_slice,
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math::Vector,
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ray::{RayBatch, RayStack},
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timer::Timer,
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};
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use super::{
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bvh_base::{BVHBase, BVHBaseNode, BVH_MAX_DEPTH},
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ACCEL_NODE_RAY_TESTS, ACCEL_TRAV_TIME,
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};
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use bvh_order::{calc_traversal_code, SplitAxes, TRAVERSAL_TABLE};
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pub fn ray_code(dir: Vector) -> usize {
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let ray_sign_is_neg = [dir.x() < 0.0, dir.y() < 0.0, dir.z() < 0.0];
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ray_sign_is_neg[0] as usize
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+ ((ray_sign_is_neg[1] as usize) << 1)
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+ ((ray_sign_is_neg[2] as usize) << 2)
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}
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#[derive(Copy, Clone, Debug)]
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pub struct BVH4<'a> {
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root: Option<&'a BVH4Node<'a>>,
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depth: usize,
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node_count: usize,
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_bounds: Option<&'a [BBox]>,
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}
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#[derive(Copy, Clone, Debug)]
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pub enum BVH4Node<'a> {
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Internal {
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bounds: &'a [BBox4],
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children: &'a [BVH4Node<'a>],
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traversal_code: u8,
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},
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Leaf {
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object_range: (usize, usize),
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},
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}
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impl<'a> BVH4<'a> {
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pub fn from_objects<'b, T, F>(
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arena: &'a MemArena,
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objects: &mut [T],
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objects_per_leaf: usize,
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bounder: F,
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) -> BVH4<'a>
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where
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F: 'b + Fn(&T) -> &'b [BBox],
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{
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if objects.len() == 0 {
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BVH4 {
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root: None,
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depth: 0,
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node_count: 0,
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_bounds: None,
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}
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} else {
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let base = BVHBase::from_objects(objects, objects_per_leaf, bounder);
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let fill_node = unsafe { arena.alloc_uninitialized_with_alignment::<BVH4Node>(32) };
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let node_count = BVH4::construct_from_base(
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arena,
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&base,
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&base.nodes[base.root_node_index()],
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fill_node,
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);
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BVH4 {
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root: Some(fill_node),
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depth: (base.depth / 2) + 1,
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node_count: node_count,
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_bounds: {
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let range = base.nodes[base.root_node_index()].bounds_range();
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Some(arena.copy_slice(&base.bounds[range.0..range.1]))
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},
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}
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}
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}
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pub fn tree_depth(&self) -> usize {
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self.depth
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}
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pub fn traverse<T, F>(
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&self,
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rays: &mut RayBatch,
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ray_stack: &mut RayStack,
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objects: &[T],
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mut obj_ray_test: F,
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) where
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F: FnMut(&T, &mut RayBatch, &mut RayStack),
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{
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if self.root.is_none() {
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return;
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}
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let mut trav_time: f64 = 0.0;
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let mut timer = Timer::new();
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let traversal_table =
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&TRAVERSAL_TABLE[ray_code(rays.dir_inv_local(ray_stack.next_task_ray_idx(0)))];
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// +2 of max depth for root and last child
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let mut node_stack = [self.root.unwrap(); (BVH_MAX_DEPTH * 3) + 2];
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let mut stack_ptr = 1;
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while stack_ptr > 0 {
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match node_stack[stack_ptr] {
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&BVH4Node::Internal {
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bounds,
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children,
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traversal_code,
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} => {
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let mut all_hits = 0;
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// Ray testing
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ray_stack.pop_do_next_task(children.len(), |ray_idx| {
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if rays.is_done(ray_idx) {
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([0, 1, 2, 3, 4, 5, 6, 7], 0)
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} else {
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let hits = lerp_slice(bounds, rays.time(ray_idx))
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.intersect_ray(
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rays.orig_local(ray_idx),
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rays.dir_inv_local(ray_idx),
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rays.max_t(ray_idx),
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)
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.to_bitmask();
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if hits != 0 {
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all_hits |= hits;
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let mut lanes = [0u8; 8];
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let mut lane_count = 0;
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for i in 0..children.len() {
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if (hits >> i) & 1 != 0 {
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lanes[lane_count] = i as u8;
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lane_count += 1;
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}
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}
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(lanes, lane_count)
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} else {
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([0, 1, 2, 3, 4, 5, 6, 7], 0)
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}
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}
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});
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// If there were any intersections, create tasks.
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if all_hits > 0 {
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let order_code = traversal_table[traversal_code as usize];
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let mut lanes = [0usize; 4];
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let mut lane_count = 0;
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for i in 0..children.len() {
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let inv_i = (children.len() - 1) - i;
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let child_i = ((order_code >> (inv_i * 2)) & 3) as usize;
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if ((all_hits >> child_i) & 1) != 0 {
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node_stack[stack_ptr + lane_count] = &children[child_i];
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lanes[lane_count] = child_i;
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lane_count += 1;
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}
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}
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ray_stack.push_lanes_to_tasks(&lanes[..lane_count]);
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stack_ptr += lane_count - 1;
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} else {
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stack_ptr -= 1;
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}
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}
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&BVH4Node::Leaf { object_range } => {
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trav_time += timer.tick() as f64;
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// Set up the tasks for each object.
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let obj_count = object_range.1 - object_range.0;
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for _ in 0..(obj_count - 1) {
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ray_stack.duplicate_next_task();
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}
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// Do the ray tests.
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for obj in &objects[object_range.0..object_range.1] {
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obj_ray_test(obj, rays, ray_stack);
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}
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timer.tick();
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stack_ptr -= 1;
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}
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}
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}
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trav_time += timer.tick() as f64;
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ACCEL_TRAV_TIME.with(|att| {
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let v = att.get();
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att.set(v + trav_time);
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});
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}
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fn construct_from_base(
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arena: &'a MemArena,
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base: &BVHBase,
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node: &BVHBaseNode,
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fill_node: &mut BVH4Node<'a>,
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) -> usize {
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let mut node_count = 0;
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match node {
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// Create internal node
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&BVHBaseNode::Internal {
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bounds_range: _,
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children_indices,
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split_axis,
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} => {
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let child_l = &base.nodes[children_indices.0];
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let child_r = &base.nodes[children_indices.1];
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// Prepare convenient access to the stuff we need.
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let child_count: usize;
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let children; // [Optional, Optional, Optional, Optional]
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let split_info: SplitAxes;
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match *child_l {
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BVHBaseNode::Internal {
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children_indices: i_l,
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split_axis: s_l,
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..
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} => {
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match *child_r {
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BVHBaseNode::Internal {
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children_indices: i_r,
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split_axis: s_r,
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..
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} => {
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// Four nodes
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child_count = 4;
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children = [
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Some(&base.nodes[i_l.0]),
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Some(&base.nodes[i_l.1]),
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Some(&base.nodes[i_r.0]),
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Some(&base.nodes[i_r.1]),
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];
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split_info = SplitAxes::Full((split_axis, s_l, s_r));
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}
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BVHBaseNode::Leaf { .. } => {
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// Three nodes with left split
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child_count = 3;
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children = [
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Some(&base.nodes[i_l.0]),
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Some(&base.nodes[i_l.1]),
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Some(child_r),
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None,
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];
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split_info = SplitAxes::Left((split_axis, s_l));
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}
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}
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}
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BVHBaseNode::Leaf { .. } => {
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match *child_r {
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BVHBaseNode::Internal {
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children_indices: i_r,
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split_axis: s_r,
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..
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} => {
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// Three nodes with right split
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child_count = 3;
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children = [
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Some(child_l),
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Some(&base.nodes[i_r.0]),
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Some(&base.nodes[i_r.1]),
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None,
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];
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split_info = SplitAxes::Right((split_axis, s_r));
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}
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BVHBaseNode::Leaf { .. } => {
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// Two nodes
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child_count = 2;
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children = [Some(child_l), Some(child_r), None, None];
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split_info = SplitAxes::TopOnly(split_axis);
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}
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}
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}
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}
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node_count += child_count;
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// Construct bounds
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let bounds = {
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let bounds_len = children
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.iter()
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.map(|c| {
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if let &Some(n) = c {
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let len = n.bounds_range().1 - n.bounds_range().0;
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debug_assert!(len >= 1);
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len
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} else {
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0
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}
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})
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.max()
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.unwrap();
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debug_assert!(bounds_len >= 1);
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let bounds =
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unsafe { arena.alloc_array_uninitialized_with_alignment(bounds_len, 32) };
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if bounds_len < 2 {
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let b1 =
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children[0].map_or(BBox::new(), |c| base.bounds[c.bounds_range().0]);
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let b2 =
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children[1].map_or(BBox::new(), |c| base.bounds[c.bounds_range().0]);
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let b3 =
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children[2].map_or(BBox::new(), |c| base.bounds[c.bounds_range().0]);
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let b4 =
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children[3].map_or(BBox::new(), |c| base.bounds[c.bounds_range().0]);
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bounds[0] = BBox4::from_bboxes(b1, b2, b3, b4);
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} else {
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for (i, b) in bounds.iter_mut().enumerate() {
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let time = i as f32 / (bounds_len - 1) as f32;
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let b1 = children[0].map_or(BBox::new(), |c| {
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let (x, y) = c.bounds_range();
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lerp_slice(&base.bounds[x..y], time)
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});
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let b2 = children[1].map_or(BBox::new(), |c| {
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let (x, y) = c.bounds_range();
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lerp_slice(&base.bounds[x..y], time)
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});
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let b3 = children[2].map_or(BBox::new(), |c| {
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let (x, y) = c.bounds_range();
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lerp_slice(&base.bounds[x..y], time)
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});
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let b4 = children[3].map_or(BBox::new(), |c| {
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let (x, y) = c.bounds_range();
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lerp_slice(&base.bounds[x..y], time)
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});
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*b = BBox4::from_bboxes(b1, b2, b3, b4);
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}
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}
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bounds
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};
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// Construct child nodes
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let child_nodes = unsafe {
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arena.alloc_array_uninitialized_with_alignment::<BVH4Node>(child_count, 32)
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};
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for (i, c) in children[0..child_count].iter().enumerate() {
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node_count +=
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BVH4::construct_from_base(arena, base, c.unwrap(), &mut child_nodes[i]);
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}
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// Build this node
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*fill_node = BVH4Node::Internal {
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bounds: bounds,
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children: child_nodes,
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traversal_code: calc_traversal_code(split_info),
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};
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}
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// Create internal node
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&BVHBaseNode::Leaf { object_range, .. } => {
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*fill_node = BVH4Node::Leaf {
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object_range: object_range,
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};
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node_count += 1;
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}
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}
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return node_count;
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}
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}
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impl<'a> Boundable for BVH4<'a> {
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fn bounds<'b>(&'b self) -> &'b [BBox] {
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self._bounds.unwrap_or(&[])
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}
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}
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@ -1,5 +1,6 @@
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// mod bvh;
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mod bvh4;
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mod bvh4_simd;
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mod bvh_base;
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mod light_array;
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mod light_tree;
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@ -14,7 +15,7 @@ use crate::{
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pub use self::{
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// bvh::{BVHNode, BVH},
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bvh4::{ray_code, BVH4Node, BVH4},
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bvh4_simd::{ray_code, BVH4Node, BVH4},
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light_array::LightArray,
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light_tree::LightTree,
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};
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139
src/bbox4.rs
Normal file
139
src/bbox4.rs
Normal file
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@ -0,0 +1,139 @@
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#![allow(dead_code)]
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use std;
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use std::ops::{BitOr, BitOrAssign};
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use crate::{
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bbox::BBox,
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lerp::{lerp, Lerp},
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math::{Point, Vector},
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};
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use float4::{Bool4, Float4};
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const BBOX_MAXT_ADJUST: f32 = 1.00000024;
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/// A SIMD set of 4 3D axis-aligned bounding boxes.
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#[derive(Debug, Copy, Clone)]
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pub struct BBox4 {
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pub x: (Float4, Float4), // (min, max)
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pub y: (Float4, Float4), // (min, max)
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pub z: (Float4, Float4), // (min, max)
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}
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impl BBox4 {
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/// Creates a degenerate BBox with +infinity min and -infinity max.
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pub fn new() -> BBox4 {
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BBox4 {
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x: (
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Float4::splat(std::f32::INFINITY),
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Float4::splat(std::f32::NEG_INFINITY),
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),
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y: (
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Float4::splat(std::f32::INFINITY),
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Float4::splat(std::f32::NEG_INFINITY),
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),
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z: (
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Float4::splat(std::f32::INFINITY),
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Float4::splat(std::f32::NEG_INFINITY),
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),
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}
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}
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/// Creates a BBox with min as the minimum extent and max as the maximum
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/// extent.
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pub fn from_bboxes(b1: BBox, b2: BBox, b3: BBox, b4: BBox) -> BBox4 {
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BBox4 {
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x: (
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Float4::new(b1.min.x(), b2.min.x(), b3.min.x(), b4.min.x()),
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Float4::new(b1.max.x(), b2.max.x(), b3.max.x(), b4.max.x()),
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),
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y: (
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Float4::new(b1.min.y(), b2.min.y(), b3.min.y(), b4.min.y()),
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Float4::new(b1.max.y(), b2.max.y(), b3.max.y(), b4.max.y()),
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),
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z: (
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Float4::new(b1.min.z(), b2.min.z(), b3.min.z(), b4.min.z()),
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Float4::new(b1.max.z(), b2.max.z(), b3.max.z(), b4.max.z()),
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),
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}
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}
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// Returns whether the given ray intersects with the bboxes.
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pub fn intersect_ray(&self, orig: Point, dir_inv: Vector, max_t: f32) -> Bool4 {
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// Get the ray data into SIMD format.
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let ro_x = orig.co.all_0();
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let ro_y = orig.co.all_1();
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let ro_z = orig.co.all_2();
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let rdi_x = dir_inv.co.all_0();
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let rdi_y = dir_inv.co.all_1();
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let rdi_z = dir_inv.co.all_2();
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let max_t = Float4::splat(max_t);
|
||||
|
||||
// Slab tests
|
||||
let t1_x = (self.x.0 - ro_x) * rdi_x;
|
||||
let t1_y = (self.y.0 - ro_y) * rdi_y;
|
||||
let t1_z = (self.z.0 - ro_z) * rdi_z;
|
||||
let t2_x = (self.x.1 - ro_x) * rdi_x;
|
||||
let t2_y = (self.y.1 - ro_y) * rdi_y;
|
||||
let t2_z = (self.z.1 - ro_z) * rdi_z;
|
||||
|
||||
// Get the far and near t hits for each axis.
|
||||
let t_far_x = t1_x.v_max(t2_x);
|
||||
let t_far_y = t1_y.v_max(t2_y);
|
||||
let t_far_z = t1_z.v_max(t2_z);
|
||||
let t_near_x = t1_x.v_min(t2_x);
|
||||
let t_near_y = t1_y.v_min(t2_y);
|
||||
let t_near_z = t1_z.v_min(t2_z);
|
||||
|
||||
// Calculate over-all far t hit.
|
||||
let far_t =
|
||||
(t_far_x.v_min(t_far_y.v_min(t_far_z)) * Float4::splat(BBOX_MAXT_ADJUST)).v_min(max_t);
|
||||
|
||||
// Calculate over-all near t hit.
|
||||
let near_t = t_near_x
|
||||
.v_max(t_near_y)
|
||||
.v_max(t_near_z.v_max(Float4::splat(0.0)));
|
||||
|
||||
// Hit results
|
||||
near_t.lt(far_t)
|
||||
}
|
||||
}
|
||||
|
||||
/// Union of two BBoxes.
|
||||
impl BitOr for BBox4 {
|
||||
type Output = BBox4;
|
||||
|
||||
fn bitor(self, rhs: BBox4) -> BBox4 {
|
||||
BBox4 {
|
||||
x: (self.x.0.v_min(rhs.x.0), self.x.1.v_max(rhs.x.1)),
|
||||
y: (self.y.0.v_min(rhs.y.0), self.y.1.v_max(rhs.y.1)),
|
||||
z: (self.z.0.v_min(rhs.z.0), self.z.1.v_max(rhs.z.1)),
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
impl BitOrAssign for BBox4 {
|
||||
fn bitor_assign(&mut self, rhs: BBox4) {
|
||||
*self = *self | rhs;
|
||||
}
|
||||
}
|
||||
|
||||
impl Lerp for BBox4 {
|
||||
fn lerp(self, other: BBox4, alpha: f32) -> BBox4 {
|
||||
BBox4 {
|
||||
x: (
|
||||
lerp(self.x.0, other.x.0, alpha),
|
||||
lerp(self.x.1, other.x.1, alpha),
|
||||
),
|
||||
y: (
|
||||
lerp(self.y.0, other.y.0, alpha),
|
||||
lerp(self.y.1, other.y.1, alpha),
|
||||
),
|
||||
z: (
|
||||
lerp(self.z.0, other.z.0, alpha),
|
||||
lerp(self.z.1, other.z.1, alpha),
|
||||
),
|
||||
}
|
||||
}
|
||||
}
|
||||
|
|
@ -17,6 +17,7 @@ extern crate lazy_static;
|
|||
mod accel;
|
||||
mod algorithm;
|
||||
mod bbox;
|
||||
mod bbox4;
|
||||
mod boundable;
|
||||
mod camera;
|
||||
mod color;
|
||||
|
|
|
|||
19
src/ray.rs
19
src/ray.rs
|
|
@ -273,6 +273,25 @@ impl RayStack {
|
|||
}
|
||||
}
|
||||
|
||||
pub fn duplicate_next_task(&mut self) {
|
||||
let task = self.tasks.last().unwrap();
|
||||
let l = task.lane;
|
||||
let start = task.start_idx;
|
||||
let end = self.lanes[l].end_len;
|
||||
|
||||
for i in start..end {
|
||||
let idx = self.lanes[l].idxs[i];
|
||||
self.lanes[l].idxs.push(idx);
|
||||
}
|
||||
|
||||
self.tasks.push(RayTask {
|
||||
lane: l,
|
||||
start_idx: end,
|
||||
});
|
||||
|
||||
self.lanes[l].end_len = self.lanes[l].idxs.len();
|
||||
}
|
||||
|
||||
/// Pops the next task off the stack, and executes the provided closure for
|
||||
/// each ray index in the task. The return value of the closure is the list
|
||||
/// of lanes (by index) to add the given ray index back into.
|
||||
|
|
|
|||
Loading…
Reference in New Issue
Block a user