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hairparticle: reduced buffer creation, optimizations
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@turanszkij
turanszkij committed Feb 19, 2025
1 parent 7c93a17 commit df0d0fc
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Showing 8 changed files with 102 additions and 100 deletions.
4 changes: 3 additions & 1 deletion WickedEngine/shaders/ShaderInterop_HairParticle.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6,10 +6,12 @@

#define THREADCOUNT_SIMULATEHAIR 64

struct PatchSimulationData
struct alignas(16) PatchSimulationData
{
float3 prevTail;
float padding0;
float3 currentTail;
float padding1;
};

enum HAIR_FLAGS
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4 changes: 4 additions & 0 deletions WickedEngine/shaders/globals.hlsli
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Original file line number Diff line number Diff line change
Expand Up @@ -904,7 +904,11 @@ inline void draw_line(float3 a, float3 b, float4 color = 1)
debugline.posB = float4(b, 1);
debugline.colorA = color;
debugline.colorB = color;
#ifdef __PSSL__
indirect_debug_buffer.TypedStore<DebugLine>(sizeof(IndirectDrawArgsInstanced) + sizeof(DebugLine) * prevCount / 2, debugline);
#else
indirect_debug_buffer.Store<DebugLine>(sizeof(IndirectDrawArgsInstanced) + sizeof(DebugLine) * prevCount / 2, debugline);
#endif // __PSSL__
}
inline void draw_point(float3 pos, float size = 1, float4 color = 1)
{
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115 changes: 72 additions & 43 deletions WickedEngine/shaders/hairparticle_simulateCS.hlsl
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Original file line number Diff line number Diff line change
Expand Up @@ -2,14 +2,14 @@
#include "hairparticleHF.hlsli"
#include "ShaderInterop_HairParticle.h"

static const float3 HAIRPATCH[] = {
static const half3 HAIRPATCH[] = {
// root (for every strand):
float3(-1, -1, 0),
float3(1, -1, 0),
half3(-1, -1, 0),
half3(1, -1, 0),

// cap (for every segment of every strand):
float3(-1, 1, 0),
float3(1, 1, 0),
half3(-1, 1, 0),
half3(1, 1, 0),
};

Buffer<uint> meshIndexBuffer : register(t0);
Expand All @@ -24,12 +24,15 @@ RWBuffer<uint> culledIndexBuffer : register(u3);
RWStructuredBuffer<IndirectDrawArgsIndexedInstanced> indirectBuffer : register(u4);
RWBuffer<float4> vertexBuffer_POS_RT : register(u5);
RWBuffer<float4> vertexBuffer_NOR : register(u6);
RWBuffer<uint> primitiveBuffer : register(u7);

[numthreads(THREADCOUNT_SIMULATEHAIR, 1, 1)]
void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIndex : SV_GroupIndex)
{
if (DTid.x >= xHairStrandCount)
return;

const bool regenerate_frame = xHairFlags & HAIR_FLAG_REGENERATE_FRAME;

ShaderGeometry geometry = HairGetGeometry();

Expand Down Expand Up @@ -73,7 +76,7 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
float3 position = attribute_at_bary(pos0, pos1, pos2, bary);
position = mul(xHairBaseMeshUnormRemap.GetMatrix(), float4(position, 1)).xyz;
half3 target = normalize(attribute_at_bary(nor0, nor1, nor2, bary));
target = normalize(mul((half3x3)worldMatrix, target));
target = normalize(mul(xHairTransform.GetMatrixAdjoint(), target));
half3 tangent = normalize(mul(half3(hemispherepoint_cos(rng.next_float(), rng.next_float()).xy, 0), get_tangentspace(target)));
half3 binormal = cross(target, tangent);
half strand_length = attribute_at_bary(length0, length1, length2, bary);
Expand All @@ -96,16 +99,20 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
len *= atlas_rect.size;
len /= (half)xHairSegmentCount;
const float2 frame = float2(atlas_rect.aspect * xHairAspect * xHairSegmentCount, 1) * len * 0.5;
const float segment_radius = max(frame.x, frame.y);

const uint gfx_vertexcount_per_strand = (xHairSegmentCount * 2 + 2) * xHairBillboardCount;
const uint gfx_indexcount_per_particle = 6 * xHairBillboardCount;
uint v0 = DTid.x * gfx_vertexcount_per_strand;
const uint gfx_indexcount_per_strand = gfx_indexcount_per_particle * xHairSegmentCount;
const uint index0 = DTid.x * gfx_indexcount_per_strand;
const uint vertexID0 = DTid.x * gfx_vertexcount_per_strand;
uint v0 = vertexID0;

//draw_line(base, base + tangent, float4(1, 0, 0, 1));
//draw_line(base, base + target, float4(0, 1, 0, 1));
//draw_line(base, base + binormal, float4(0, 0, 1, 1));

float3 bend = 0;
half3 bend = 0;
if (xHairFlags & HAIR_FLAG_CAMERA_BEND)
{
// Bend down to camera up vector to avoid seeing flat planes from above
Expand All @@ -117,19 +124,20 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
rng.init(uint2(xHairRandomSeed, DTid.x), 1); // reinit random for consistent billboard variation!
for (uint billboardID = 0; billboardID < xHairBillboardCount; ++billboardID)
{
float siz = billboardID == 0 ? 1 : lerp(0.2, 1, rng.next_float());
float rot = billboardID == 0 ? 0 : (rng.next_float() * PI);
float2 rot_sincos;
half siz = billboardID == 0 ? 1 : lerp(0.2, 1, rng.next_float());
half rot = billboardID == 0 ? 0 : (rng.next_float() * PI);
half2 rot_sincos;
sincos(rot, rot_sincos.x, rot_sincos.y);
float3x3 variationMatrix = float3x3(
half3x3 variationMatrix = half3x3(
rot_sincos.y * siz, 0, -rot_sincos.x,
0, siz, 0,
rot_sincos.x, 0, rot_sincos.y * siz
);
variationMatrix = mul(variationMatrix, TBN);

for (uint vertexID = 0; vertexID < 2; ++vertexID)
{
float3 patchPos = HAIRPATCH[vertexID];
half3 patchPos = HAIRPATCH[vertexID];
float2 uv = patchPos.xy;
uv = uv * float2(0.5, 0.5) + 0.5;
uv.y = 1 - uv.y;
Expand All @@ -144,9 +152,6 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
// variation based on billboardID:
patchPos = mul(patchPos, variationMatrix);

// rotate the patch into the tangent space of the emitting triangle:
patchPos = mul(patchPos, TBN);

float3 position = base + patchPos;

if (xHairFlags & HAIR_FLAG_UNORM_POS)
Expand All @@ -168,20 +173,20 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
}
}

const float dt = clamp(GetFrame().delta_time, 0, 1.0 / 30.0); // clamp delta time to avoid simulation blowing up
const half dt = clamp(GetFrame().delta_time, 0, 1.0 / 30.0); // clamp delta time to avoid simulation blowing up

const float gravityPower = xHairGravityPower;
const float stiffnessForce = xHairStiffness;
const float dragForce = xHairDrag;
const float3 boneAxis = target;
const float boneLength = len;
const half gravityPower = xHairGravityPower;
const half stiffnessForce = xHairStiffness;
const half dragForce = xHairDrag;
const half3 boneAxis = target;
const half boneLength = len;

for (uint segmentID = 0; segmentID < xHairSegmentCount; ++segmentID)
for (uint segmentID = 0; !distance_culled && (segmentID < xHairSegmentCount); ++segmentID)
{
// Identifies the hair strand segment particle:
const uint particleID = strandID + segmentID;

if (xHairFlags & HAIR_FLAG_REGENERATE_FRAME)
if (regenerate_frame)
{
float3 tail = base + boneAxis * boneLength;
simulationBuffer[particleID].prevTail = tail;
Expand All @@ -190,19 +195,19 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn

float3 tail_current = simulationBuffer[particleID].currentTail;
float3 tail_prev = simulationBuffer[particleID].prevTail;
float3 inertia = (tail_current - tail_prev) * (1 - dragForce);
float3 stiffness = boneAxis * stiffnessForce;
float3 external = gravityPower * float3(0, -1, 0);
float3 wind = sample_wind(tail_current, ((float)segmentID + 1) / (float)xHairSegmentCount);
half3 inertia = (tail_current - tail_prev) * (1 - dragForce);
half3 stiffness = boneAxis * stiffnessForce;
half3 external = gravityPower * float3(0, -1, 0);
half3 wind = sample_wind(tail_current, ((float)segmentID + 1) / (float)xHairSegmentCount);
external += wind;

float3 tail_next = tail_current + inertia + dt * (stiffness + external);
float3 to_tail = normalize(tail_next - base);
half3 to_tail = normalize(tail_next - base);
tail_next = base + to_tail * boneLength;

//draw_sphere(tail_next, len);

// Accumulate forces, apply colliders:
// Apply every force and collider:
for (uint i = forces().first_item(); i < forces().end_item(); ++i)
{
ShaderEntity entity = load_entity(i);
Expand All @@ -217,7 +222,7 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
{
float3 A = entity.position;
float3 B = entity.GetColliderTip();
float3 N = normalize(A - B);
half3 N = normalize(A - B);
A -= N * range;
B += N * range;
//if (DTid.x == 0)
Expand All @@ -229,7 +234,7 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
float3 dir = C - tail_next;
float dist = length(dir);
dir /= dist;
dist = dist - range - len * 0.5;
dist = dist - range - segment_radius;
if (dist < 0)
{
tail_next += dir * dist;
Expand Down Expand Up @@ -257,7 +262,7 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
tail_next = base + to_tail * boneLength;
break;
case ENTITY_TYPE_COLLIDER_SPHERE:
dist = dist - range - len;
dist = dist - range - segment_radius;
if (dist < 0)
{
tail_next += dir * dist;
Expand All @@ -273,7 +278,7 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
dir *= -1;
dist = abs(dist);
}
dist = dist - len;
dist = dist - segment_radius;
if (dist < 0)
{
float4x4 planeProjection = load_entitymatrix(entity.GetMatrixIndex());
Expand Down Expand Up @@ -325,19 +330,20 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
rng.init(uint2(xHairRandomSeed, DTid.x), 1); // reinit random for consistent billboard variation!
for(uint billboardID = 0; billboardID < xHairBillboardCount; ++billboardID)
{
float siz = billboardID == 0 ? 1 : lerp(0.2, 1, rng.next_float());
float rot = billboardID == 0 ? 0 : (rng.next_float() * PI);
float2 rot_sincos;
half siz = billboardID == 0 ? 1 : lerp(0.2, 1, rng.next_float());
half rot = billboardID == 0 ? 0 : (rng.next_float() * PI);
half2 rot_sincos;
sincos(rot, rot_sincos.x, rot_sincos.y);
float3x3 variationMatrix = float3x3(
half3x3 variationMatrix = half3x3(
rot_sincos.y * siz, 0, -rot_sincos.x,
0, siz, 0,
rot_sincos.x, 0, rot_sincos.y * siz
);
variationMatrix = mul(variationMatrix, TBN);

for (uint vertexID = 2; vertexID < 4; ++vertexID)
{
float3 patchPos = HAIRPATCH[vertexID];
half3 patchPos = HAIRPATCH[vertexID];
float2 uv = patchPos.xy;
uv = uv * float2(0.5, 0.5) + 0.5;
uv.y = lerp((float)segmentID / (float)xHairSegmentCount, ((float)segmentID + 1) / (float)xHairSegmentCount, uv.y);
Expand All @@ -353,9 +359,6 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
// variation based on billboardID:
patchPos = mul(patchPos, variationMatrix);

// rotate the patch into the tangent space of the emitting triangle:
patchPos = mul(patchPos, TBN);

float3 position = base + patchPos;

if (xHairFlags & HAIR_FLAG_UNORM_POS)
Expand All @@ -380,7 +383,8 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
// Frustum culling:
ShaderSphere sphere;
sphere.center = (base + tail_next) * 0.5;
sphere.radius = len;
sphere.radius = segment_radius;
//draw_sphere(sphere.center, sphere.radius);

const bool visible = !distance_culled && GetCamera().frustum.intersects(sphere);

Expand Down Expand Up @@ -413,4 +417,29 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
base = tail_next;
target = normal;
}

// Primitive buffer creation is done here instead of CPU to reduce CPU time spent in buffer creations:
if (regenerate_frame)
{
uint i = index0;
v0 = vertexID0;
uint rootOffset = v0;
uint capOffset = rootOffset + 2 * xHairBillboardCount;
for (uint billboardID = 0; billboardID < xHairBillboardCount; ++billboardID)
{
for (uint segmentID = 0; segmentID < xHairSegmentCount; ++segmentID)
{
primitiveBuffer[i++] = rootOffset + 0;
primitiveBuffer[i++] = rootOffset + 1;
primitiveBuffer[i++] = capOffset + 0;
primitiveBuffer[i++] = capOffset + 0;
primitiveBuffer[i++] = rootOffset + 1;
primitiveBuffer[i++] = capOffset + 1;
rootOffset += 2;
capOffset += 2;
v0 += 2;
}
v0 += 2;
}
}
}
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