Files
UnrealEngine/Engine/Shaders/Private/BitPacking.ush
2025-05-18 13:04:45 +08:00

297 lines
9.1 KiB
HLSL

// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
uint3 UnpackToUint3(uint Value, uint3 NumComponentBits)
{
return uint3(BitFieldExtractU32(Value, NumComponentBits.x, 0),
BitFieldExtractU32(Value, NumComponentBits.y, NumComponentBits.x),
BitFieldExtractU32(Value, NumComponentBits.z, NumComponentBits.x + NumComponentBits.y));
}
uint4 UnpackToUint4(uint Value, uint4 NumComponentBits)
{
return uint4(BitFieldExtractU32(Value, NumComponentBits.x, 0),
BitFieldExtractU32(Value, NumComponentBits.y, NumComponentBits.x),
BitFieldExtractU32(Value, NumComponentBits.z, NumComponentBits.x + NumComponentBits.y),
BitFieldExtractU32(Value, NumComponentBits.w, NumComponentBits.x + NumComponentBits.y + NumComponentBits.z));
}
float3 UnpackToFloat3(uint Value, uint3 NumComponentBits)
{
checkSlow(NumComponentBits.x + NumComponentBits.y + NumComponentBits.z <= 32u);
return float3(BitFieldExtractFloat(Value, NumComponentBits.x, 0),
BitFieldExtractFloat(Value, NumComponentBits.y, NumComponentBits.x),
BitFieldExtractFloat(Value, NumComponentBits.z, NumComponentBits.x + NumComponentBits.y));
}
float3 UnpackToFloat3(uint Value, uint BitsPerElement)
{
return UnpackToFloat3(Value, uint3(BitsPerElement, BitsPerElement, BitsPerElement));
}
uint FloatToUIntScaled(float Value, float Scale)
{
return (uint)floor(Value * Scale + 0.5f);
}
uint Pack_Float4_To_R10G10B10A2_UNORM(float4 Unpacked)
{
const float4 UnpackedClamped = saturate(Unpacked);
uint Packed = ((FloatToUIntScaled(UnpackedClamped.x, 1023)) |
(FloatToUIntScaled(UnpackedClamped.y, 1023) << 10) |
(FloatToUIntScaled(UnpackedClamped.z, 1023) << 20) |
(FloatToUIntScaled(UnpackedClamped.w, 3) << 30));
return Packed;
}
float4 Unpack_R10G10B10A2_UNORM_To_Float4(uint Packed)
{
float4 Unpacked;
Unpacked.x = (float)(((Packed ) & 0x000003FF)) / 1023;
Unpacked.y = (float)(((Packed >> 10) & 0x000003FF)) / 1023;
Unpacked.z = (float)(((Packed >> 20) & 0x000003FF)) / 1023;
Unpacked.w = (float)(((Packed >> 30) & 0x00000003)) / 3;
return Unpacked;
}
/**
* Pack normalized, i.e., range [0..1], float value to uint at a certain number of bits, rounding down.
*/
uint PackNormToUintFloor(float FloatNorm, uint BitsPerElement)
{
return uint(floor(FloatNorm * float((1u << BitsPerElement) - 1u)));
}
/**
* Pack normalized, i.e., range [0..1], float value to uint at a certain number of bits, rounding up.
*/
uint PackNormToUintCeil(float FloatNorm, uint BitsPerElement)
{
return uint(ceil(FloatNorm * float((1u << BitsPerElement) - 1u)));
}
/**
* Pack uint3 into uint at a certain number of bits.
*/
uint PackToUint(uint3 Packed3, uint3 NumComponentBits)
{
checkSlow(NumComponentBits.x + NumComponentBits.y + NumComponentBits.z <= 32u);
return Packed3.x | (Packed3.y << NumComponentBits.x) | (Packed3.z << (NumComponentBits.x + NumComponentBits.y));
}
/**
* Pack normalized, i.e., range [0..1], float3 value to uint at a certain number of bits per component, rounding down.
*/
uint PackNormToUintFloor(float3 FloatNorm, uint3 NumComponentBits)
{
return PackToUint(
uint3(
PackNormToUintFloor(FloatNorm.x, NumComponentBits.x),
PackNormToUintFloor(FloatNorm.y, NumComponentBits.y),
PackNormToUintFloor(FloatNorm.z, NumComponentBits.z)
),
NumComponentBits);
}
uint PackNormToUintFloor(float3 FloatNorm, uint BitsPerElement)
{
return PackNormToUintFloor(FloatNorm, uint3(BitsPerElement, BitsPerElement, BitsPerElement));
}
/**
* Pack normalized, i.e., range [0..1], float3 value to uint at a certain number of bits per component, rounding up.
*/
uint PackNormToUintCeil(float3 FloatNorm, uint3 NumComponentBits)
{
return PackToUint(
uint3(
PackNormToUintCeil(FloatNorm.x, NumComponentBits.x),
PackNormToUintCeil(FloatNorm.y, NumComponentBits.y),
PackNormToUintCeil(FloatNorm.z, NumComponentBits.z)
),
NumComponentBits);
}
uint PackNormToUintCeil(float3 FloatNorm, uint BitsPerElement)
{
return PackNormToUintCeil(FloatNorm, uint3(BitsPerElement,BitsPerElement,BitsPerElement));
}
// Implement BitStreamReader for ByteAddressBuffer (RO), RWByteAddressBuffer (RW) and dynamic choice (RORW).
struct FBitStreamReaderState
{
uint AlignedByteAddress;
int BitOffsetFromAddress;
uint4 BufferBits;
int BufferOffset;
int CompileTimeMinBufferBits;
int CompileTimeMinDwordBits;
int CompileTimeMaxRemainingBits;
};
FBitStreamReaderState BitStreamReader_Create_Aligned(uint AlignedByteAddress, uint BitOffset, uint CompileTimeMaxRemainingBits)
{
FBitStreamReaderState State;
State.AlignedByteAddress = AlignedByteAddress;
State.BitOffsetFromAddress = BitOffset;
State.BufferBits = 0;
State.BufferOffset = 0;
State.CompileTimeMinBufferBits = 0;
State.CompileTimeMinDwordBits = 0;
State.CompileTimeMaxRemainingBits = CompileTimeMaxRemainingBits;
return State;
}
FBitStreamReaderState BitStreamReader_Create(uint ByteAddress, uint BitOffset, uint CompileTimeMaxRemainingBits)
{
uint AlignedByteAddress = ByteAddress & ~3u;
BitOffset += (ByteAddress & 3u) << 3;
return BitStreamReader_Create_Aligned(AlignedByteAddress, BitOffset, CompileTimeMaxRemainingBits);
}
#define TYPE_SUFFIX RO
#define INPUT_BUFFER_TYPE ByteAddressBuffer
#include "BitStreamReaderImplementation.ush"
#undef TYPE_SUFFIX
#undef INPUT_BUFFER_TYPE
#define TYPE_SUFFIX RW
#define INPUT_BUFFER_TYPE RWByteAddressBuffer
#include "BitStreamReaderImplementation.ush"
#undef TYPE_SUFFIX
#undef INPUT_BUFFER_TYPE
// Put bits to ByteAddressBuffer at bit offset. NumBits must be <= 31.
void PutBits(RWByteAddressBuffer Output, uint AlignedBaseAddress, uint BitOffset, uint Value, uint NumBits)
{
uint BitOffsetInDword = (BitOffset & 31u); // &31 is implicit in shifts
uint Bits = Value << BitOffsetInDword;
uint Address = AlignedBaseAddress + ((BitOffset >> 5) << 2);
uint EndBitPos = BitOffsetInDword + NumBits;
if (EndBitPos >= 32)
{
uint Mask = 0xFFFFFFFFu << (EndBitPos & 31u);
Output.InterlockedAnd(Address + 4, Mask);
Output.InterlockedOr(Address + 4, Value >> (32 - BitOffsetInDword));
}
{
uint Mask = ~BitFieldMaskU32(NumBits, BitOffset);
Output.InterlockedAnd(Address, Mask);
Output.InterlockedOr(Address, Value << BitOffsetInDword);
}
}
struct FBitStreamWriterState
{
uint StartAlignedByteAddress;
uint StartBitOffset;
uint StartBufferBits;
uint NextAlignedByteAddress;
uint BitOffset;
uint BufferBits;
};
FBitStreamWriterState BitStreamWriter_Create_Aligned(uint AlignedBaseAddressInBytes, uint BitOffset)
{
FBitStreamWriterState State;
State.StartAlignedByteAddress = AlignedBaseAddressInBytes + ((BitOffset >> 5) << 2);
BitOffset &= 31u;
State.StartBitOffset = BitOffset;
State.StartBufferBits = 0;
State.NextAlignedByteAddress = State.StartAlignedByteAddress + 4u;
State.BitOffset = BitOffset;
State.BufferBits = 0;
return State;
}
void BitStreamWriter_Writer(RWByteAddressBuffer Output, inout FBitStreamWriterState State, uint Value, int NumBits, int CompileTimeMaxBits)
{
const uint Tmp = Value << (State.BitOffset & 31u); // & 31u is implicit
if(State.BitOffset >= 32)
State.BufferBits |= Tmp;
else
State.StartBufferBits |= Tmp;
const uint NextBitOffset = State.BitOffset + NumBits;
// Overflow to next DWORD?
if ((State.BitOffset ^ NextBitOffset) >= 32)
{
// Keep first DWORD in register, so we can merge it in with atomic later
if(State.BitOffset >= 32)
{
Output.Store(State.NextAlignedByteAddress, State.BufferBits);
State.NextAlignedByteAddress += 4;
}
State.BufferBits = (CompileTimeMaxBits < 32 || (State.BitOffset & 31)) ? (Value >> ((32u - State.BitOffset) & 31u)) : 0u;
}
State.BitOffset = NextBitOffset;
}
void BitStreamWriter_Flush(RWByteAddressBuffer Output, inout FBitStreamWriterState State)
{
// Start
const uint NumBits = State.BitOffset - State.StartBitOffset;
uint StartMask = NumBits >= 32 ? 0xFFFFFFFFu :
BitFieldMaskU32(NumBits, 0);
StartMask <<= State.StartBitOffset;
Output.InterlockedAnd(State.StartAlignedByteAddress, ~StartMask);
Output.InterlockedOr(State.StartAlignedByteAddress, State.StartBufferBits);
if (State.BitOffset > 32)
{
const uint Mask = BitFieldMaskU32(State.BitOffset & 31u, 0);
Output.InterlockedAnd(State.NextAlignedByteAddress, ~Mask);
Output.InterlockedOr(State.NextAlignedByteAddress, State.BufferBits);
}
}
// Utility functions for packing bits into uints.
// When Position and NumBits can be determined at compile time this should be just as fast as manual bit packing.
uint ReadBits(uint4 Data, inout uint Position, uint NumBits)
{
uint DwordIndex = Position >> 5;
uint BitIndex = Position & 31;
uint Value = Data[DwordIndex] >> BitIndex;
if (BitIndex + NumBits > 32)
{
Value |= Data[DwordIndex + 1] << (32 - BitIndex);
}
Position += NumBits;
uint Mask = ((1u << NumBits) - 1u);
return Value & Mask;
}
void WriteBits(inout uint4 Data, inout uint Position, uint Value, uint NumBits)
{
uint DwordIndex = Position >> 5;
uint BitIndex = Position & 31;
Data[DwordIndex] |= Value << BitIndex;
if (BitIndex + NumBits > 32)
{
Data[DwordIndex + 1] |= Value >> (32 - BitIndex);
}
Position += NumBits;
}