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radv: Add traversal backtracking with a short stack.

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So we can now work with arbitrarily deep BVHs.

Reviewed-By: Konstantin Seurer <konstantin.seurer@gmail.com>
Reviewed-by: Friedrich Vock <friedrich.vock@gmx.de>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18799>
This commit is contained in:
Bas Nieuwenhuizen
2022-09-24 14:56:06 +02:00
committed by Marge Bot
parent 251bba2fa0
commit a8abdc0d89
4 changed files with 178 additions and 104 deletions
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35
src/amd/vulkan/radv_rt_common.h
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@@ -59,17 +59,6 @@ nir_ssa_def *hit_is_opaque(nir_builder *b, nir_ssa_def *sbt_offset_and_flags, ni
nir_ssa_def *create_bvh_descriptor(nir_builder *b);
/*
* A top-level AS can contain 2^24 children and a bottom-level AS can contain 2^24
* triangles. At a branching factor of 4, that means we may need up to 24 levels of box
* nodes + 1 triangle node
* + 1 instance node. Furthermore, when processing a box node, worst case we actually
* push all 4 children and remove one, so the DFS stack depth is box nodes * 3 + 2.
*/
#define MAX_STACK_ENTRY_COUNT 76
#define MAX_STACK_LDS_ENTRY_COUNT 16
#define MAX_STACK_SCRATCH_ENTRY_COUNT (MAX_STACK_ENTRY_COUNT - MAX_STACK_LDS_ENTRY_COUNT)
struct radv_ray_traversal_args;
struct radv_leaf_intersection {
@@ -101,9 +90,6 @@ typedef void (*radv_rt_stack_store_cb)(nir_builder *b, nir_ssa_def *index, nir_s
typedef nir_ssa_def *(*radv_rt_stack_load_cb)(nir_builder *b, nir_ssa_def *index,
const struct radv_ray_traversal_args *args);
typedef void (*radv_rt_check_stack_overflow_cb)(nir_builder *b,
const struct radv_ray_traversal_args *args);
struct radv_ray_traversal_vars {
/* For each accepted hit, tmax will be set to the t value. This allows for automatic intersection
* culling.
@@ -119,13 +105,23 @@ struct radv_ray_traversal_vars {
nir_deref_instr *bvh_base;
/* stack is the current stack pointer/index. top_stack is the pointer/index that marks the end of
* traversal for the current BLAS/TLAS.
* traversal for the current BLAS/TLAS. stack_base is the low watermark of the short stack.
*/
nir_deref_instr *stack;
nir_deref_instr *top_stack;
nir_deref_instr *stack_base;
nir_deref_instr *current_node;
/* The node visited in the previous iteration. This is used in backtracking to jump to its parent
* and then find the child after the previously visited node.
*/
nir_deref_instr *previous_node;
/* When entering an instance these are the instance node and the root node of the BLAS */
nir_deref_instr *instance_top_node;
nir_deref_instr *instance_bottom_node;
/* Information about the current instance used for culling. */
nir_deref_instr *instance_id;
nir_deref_instr *instance_addr;
@@ -143,12 +139,13 @@ struct radv_ray_traversal_args {
struct radv_ray_traversal_vars vars;
/* The increment/decrement used for radv_ray_traversal_vars::stack */
/* The increment/decrement used for radv_ray_traversal_vars::stack, and how many entries are
* available. */
uint32_t stack_stride;
uint32_t stack_entries;
radv_rt_stack_store_cb stack_store_cb;
radv_rt_stack_load_cb stack_load_cb;
radv_rt_check_stack_overflow_cb check_stack_overflow_cb;
radv_aabb_intersection_cb aabb_cb;
radv_triangle_intersection_cb triangle_cb;
@@ -156,6 +153,10 @@ struct radv_ray_traversal_args {
void *data;
};
/* For the initialization of instance_bottom_node. Explicitly different than RADV_BVH_INVALID_NODE
* or any real node, to ensure we never exit an instance when we're not in one. */
#define RADV_BVH_NO_INSTANCE_ROOT 0xfffffffeu
/* Builds the ray traversal loop and returns whether traversal is incomplete, similar to
* rayQueryProceedEXT. Traversal will only be considered incomplete, if one of the specified
* callbacks breaks out of the traversal loop.