billboard_sorting.c File Reference

#include "billboard_sorting.h"
#include "gl_common.h"
#include "gl_debug.h"
#include "log.h"
#include "platform/platform_utils.h"
#include "profiler.h"
#include "shader.h"
#include <stdbool.h>
#include <stdlib.h>

Include dependency graph for billboard_sorting.c:

Enumerations
enum	{ EXPECTED_SPHERE_INSTANCE_SIZE = 128 }
enum	{ WORKGROUP_SIZE = 1024 }
enum	{ DEFAULT_MIN_CAPACITY = 64 }
enum	{ MAX_SINGLE_PASS_COUNT = 1024 }
enum	{ RADIX_BITS_PER_PASS = 8 }
enum	{ RADIX_BUCKETS = 256 }
enum	{ RADIX_SHIFT_LIMIT = 32 }
enum	{ RADIX_MASK = 0xFFU }

Functions
	_Static_assert (sizeof(SphereInstance)==EXPECTED_SPHERE_INSTANCE_SIZE, "SphereInstance size must match GLSL std430 layout (128 B)")
static int	next_pow2 (int val)
static bool	ensure_cpu_capacity (BillboardSorter *sorter, int count)
	Grow CPU scratchpads to hold at least count elements. More...
static GLuint	upload_sorted_to_ssbo (BillboardSorter *sorter, int count)
	Upload count sorted instances from the CPU temp buffer to the SSBO. More...
void	billboard_sorter_init (BillboardSorter *sorter, int initial_capacity)
	Allocates internal buffers for the sorter. More...
void	billboard_sorter_cleanup (BillboardSorter *sorter)
	Destroys the sorter context. More...
GLuint	billboard_sorter_sort_gpu (BillboardSorter *sorter, const SphereInstance *instances, int count, const vec3 camera_pos)
	Sorts the array of instances Back-to-Front (descending depth) on GPU. More...
static int	compare_sphere_entries (const void *lhs, const void *rhs)
GLuint	billboard_sorter_sort_cpu (BillboardSorter *sorter, const SphereInstance *instances, int count, const vec3 camera_pos)
	Sorts the array of instances Back-to-Front (descending depth) on CPU. More...
static uint32_t	float_to_sortable_uint (float f_val)
	Converts a float to a uint32_t that preserves order (IEEE 754). This allows sorting floats using integer radix sort. More...
GLuint	billboard_sorter_sort_cpu_radix (BillboardSorter *sorter, const SphereInstance *instances, int count, const vec3 camera_pos)
	Sorts the array of instances Back-to-Front (descending depth) using Radix Sort. More...

Variables
static const uint32_t	FLOAT_SIGN_MASK = 0x80000000U
static const uint32_t	FLOAT_COMPLEMENT_MASK = 0xFFFFFFFFU
static const unsigned int	BIT_SHIFT_8 = 8U
static const unsigned int	BIT_SHIFT_16 = 16U
static const size_t	GPU_ENTRY_SIZE = 8

Enumeration Type Documentation

anonymous enum

anonymous enum

Enumerator
EXPECTED_SPHERE_INSTANCE_SIZE

anonymous enum

anonymous enum

Enumerator
WORKGROUP_SIZE

anonymous enum

anonymous enum

Enumerator
DEFAULT_MIN_CAPACITY

anonymous enum

anonymous enum

Enumerator
MAX_SINGLE_PASS_COUNT

anonymous enum

anonymous enum

Enumerator
RADIX_BITS_PER_PASS

anonymous enum

anonymous enum

Enumerator
RADIX_BUCKETS

anonymous enum

anonymous enum

Enumerator
RADIX_SHIFT_LIMIT

anonymous enum

anonymous enum

Enumerator
RADIX_MASK

Function Documentation

_Static_assert()

_Static_assert	(	sizeof(SphereInstance)	= =EXPECTED_SPHERE_INSTANCE_SIZE,
		"SphereInstance size must match GLSL std430 layout (128 B)"
	)

billboard_sorter_cleanup()

void billboard_sorter_cleanup

(

BillboardSorter *

sorter

)

Destroys the sorter context.

Parameters

sorter

Pointer to the struct.

billboard_sorter_init()

void billboard_sorter_init	(	BillboardSorter *	sorter,
		int	initial_capacity
	)

Allocates internal buffers for the sorter.

Parameters

sorter	Pointer to the struct.
initial_capacity	Expected number of instances.

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billboard_sorter_sort_cpu()

GLuint billboard_sorter_sort_cpu	(	BillboardSorter *	sorter,
		const SphereInstance *	instances,
		int	count,
		const vec3	camera_pos
	)

Sorts the array of instances Back-to-Front (descending depth) on CPU.

Uses qsort on the host and uploads the result to the SSBO.

Parameters

sorter	Memory context.
instances	Array of instances (will be copied and sorted internally).
count	Active element count.
camera_pos	World-space viewer position.

Returns

The SSBO handle containing the sorted instances.

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billboard_sorter_sort_cpu_radix()

GLuint billboard_sorter_sort_cpu_radix	(	BillboardSorter *	sorter,
		const SphereInstance *	instances,
		int	count,
		const vec3	camera_pos
	)

Sorts the array of instances Back-to-Front (descending depth) using Radix Sort.

Parameters

sorter	Memory context.
instances	Array of instances.
count	Active element count.
camera_pos	World-space viewer position (for depth).

Returns

The SSBO handle containing the sorted instances.

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billboard_sorter_sort_gpu()

GLuint billboard_sorter_sort_gpu	(	BillboardSorter *	sorter,
		const SphereInstance *	instances,
		int	count,
		const vec3	camera_pos
	)

Sorts the array of instances Back-to-Front (descending depth) on GPU.

Uploads instances to an SSBO, sorts them using a compute shader, and prepares them for rendering.

Parameters

sorter	Memory context.
instances	Pointer to the array of instances to upload.
count	Active element count.
camera_pos	World-space viewer position.

Returns

The SSBO handle containing the sorted instances.

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compare_sphere_entries()

static int compare_sphere_entries ( const void *  lhs, const void *  rhs  )

static

ensure_cpu_capacity()

static bool ensure_cpu_capacity ( BillboardSorter *  sorter, int  count  )

static

Grow CPU scratchpads to hold at least count elements.

Returns

true on success, false on allocation failure.

float_to_sortable_uint()

static uint32_t float_to_sortable_uint ( float  f_val )

inlinestatic

Converts a float to a uint32_t that preserves order (IEEE 754). This allows sorting floats using integer radix sort.

next_pow2()

static int next_pow2 ( int  val )

static

upload_sorted_to_ssbo()

static GLuint upload_sorted_to_ssbo ( BillboardSorter *  sorter, int  count  )

static

Upload count sorted instances from the CPU temp buffer to the SSBO.

Returns

The SSBO handle containing the data.

Variable Documentation

BIT_SHIFT_16

const unsigned int BIT_SHIFT_16 = 16U

static

BIT_SHIFT_8

const unsigned int BIT_SHIFT_8 = 8U

static

Bit-shift constants for next_pow2 (named to satisfy linter).

FLOAT_COMPLEMENT_MASK

const uint32_t FLOAT_COMPLEMENT_MASK = 0xFFFFFFFFU

static

FLOAT_SIGN_MASK

const uint32_t FLOAT_SIGN_MASK = 0x80000000U

static

GPU_ENTRY_SIZE

const size_t GPU_ENTRY_SIZE = 8

static

Size of the Entry struct in the compute shader: int (4) + float (4).