[ComputeShader]实例化大网格
发表于2018-11-19
本篇文章给大家分享下使用ComputeShader实现实例化大网格，主要也是借助了ComputeShader对于运行的图形库的支持，包括DX11、DX12、OpenGL4.3+、OpenGLES3等，在涉及到大量的数学计算时，并且是可以并行的没有很多分支的计算，都可以采用ComputeShader。
最终效果
思路
图解ComputeShader
这个图片就是ComputeShader，值得注意的是Thread最多为1024个。应该是考虑到当前显卡的最低线程数的关系。
数据交换的效率
有图可鉴，数据最好是单向输出的，尽量避免交换。
网格实例化思路
- 脚本中根据核心数对需要实例化的网格进行顶点排序并记录在uv信息中，然后合并网格，也可以利用dx11的SV_InstanceID(相关API可以查看MSCN的HLSL)。
- 编写ComputeShader，利用GPU对大量数据进行实时运算。
- 编写延迟光照Shader，根据处理后的数据对网格进行实时变动。
源代码
脚本控制代码：
using UnityEngine;
using System.Collections;
using System.Runtime.InteropServices;
using System.Collections.Generic;
using UnityEngine.Assertions;
#if UNITY_EDITOR
using UnityEditor;
#endif
namespace MatrixParticle
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public struct _Particle
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Vector3 position;
Vector3 direction;
Vector3 scale;
Vector2 uv;
Vector4 color;
float lifeTime;
｝;
public class MatrixParticles : MonoBehaviour
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const int VERTEX_MAX = 65534;
public ComputeShader shader;
public Material mat;
public Mesh mesh;
[SerializeField]
private int xMod = 1, yMod = 1, zMod = 1;
[SerializeField]
private Vector3 scale = Vector3.one;
private ComputeBuffer particlesBuffer;
private int initKernal, updateKernal, emitKernal;
private int maxKernal;
private List<MaterialPropertyBlock> propertyBlocks = new List<MaterialPropertyBlock>();
private int perMeshNum, comMeshNum;
private Mesh combinedMesh;
void Start()
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maxKernal = xMod * yMod * zMod * 1000;
shader.SetInt("_xMod", xMod * 10);
shader.SetInt("_yMod", yMod * 10);
shader.SetInt("_zMod", zMod * 10);
shader.SetVector("_Scale", scale);
initKernal = shader.FindKernel("Init");
updateKernal = shader.FindKernel("Update");
emitKernal = shader.FindKernel("Emit");
particlesBuffer = new ComputeBuffer(maxKernal, Marshal.SizeOf(typeof(_Particle)), ComputeBufferType.Default);
CreateMesh();
InitParticles();
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void CreateMesh()
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perMeshNum = VERTEX_MAX / mesh.vertexCount;
comMeshNum = (int)Mathf.Ceil((float)maxKernal / perMeshNum);
combinedMesh = CreateCombinedMesh(mesh, perMeshNum);
for (int i = 0; i < comMeshNum; i++)
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MaterialPropertyBlock property = new MaterialPropertyBlock();
property.SetFloat("_Offset", perMeshNum * i);
propertyBlocks.Add(property);
｝
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void Update()
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UpdateParticles();
DrawParticles(Camera.main);
#if UNITY_EDITOR
if (SceneView.lastActiveSceneView)
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DrawParticles(SceneView.lastActiveSceneView.camera);
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#endif
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void InitParticles()
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shader.SetBuffer(initKernal, "_Particles", particlesBuffer);
shader.Dispatch(initKernal, xMod, yMod, zMod);
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void UpdateParticles()
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shader.SetFloat("_Time", Time.deltaTime);
shader.SetBuffer(updateKernal, "_Particles", particlesBuffer);
shader.Dispatch(updateKernal, xMod, yMod, zMod);
｝
public void EmitParticles(Vector3 pos, float height)
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shader.SetVector("_Pos", pos);
shader.SetFloat("_Height", -height);
shader.SetBuffer(emitKernal, "_Particles", particlesBuffer);
shader.Dispatch(emitKernal, xMod, yMod, zMod);
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void DrawParticles(Camera camera)
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mat.SetBuffer("_Particles", particlesBuffer);
for (int i = 0; i < comMeshNum; ++i)
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var props = propertyBlocks[i];
props.SetFloat("_IdOffset", perMeshNum * i);
Graphics.DrawMesh(combinedMesh, transform.position, transform.rotation, mat, 0, camera, 0, props);
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void OnDestroy()
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particlesBuffer.Release();
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Mesh CreateCombinedMesh(Mesh mesh, int num)
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int[] meshIndices = mesh.GetIndices(0);
int indexNum = meshIndices.Length;
List<Vector3> verts = new List<Vector3>();
int[] indices = new int[num * indexNum];
List<Vector3> normals = new List<Vector3>();
List<Vector4> tans = new List<Vector4>();
List<Vector2> uv0 = new List<Vector2>();
List<Vector2> uv1 = new List<Vector2>();
for (int i = 0; i < num; i++)
｛
verts.AddRange(mesh.vertices);
normals.AddRange(mesh.normals);
tans.AddRange(mesh.tangents);
uv0.AddRange(mesh.uv);
for (int n = 0; n < indexNum; n++)
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indices[i * indexNum + n] = i * mesh.vertexCount + meshIndices[n];
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for (int n = 0; n < mesh.uv.Length; n++)
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uv1.Add(new Vector2(i, i));
｝
｝
Mesh combinedMesh = new Mesh();
combinedMesh.SetVertices(verts);
combinedMesh.SetIndices(indices, MeshTopology.Triangles, 0);
combinedMesh.SetNormals(normals);
combinedMesh.SetTangents(tans);
combinedMesh.SetUVs(0, uv0);
combinedMesh.SetUVs(1, uv1);
combinedMesh.RecalculateBounds();
Vector3 size = new Vector3(xMod * 10 * scale.x, yMod * 10 * scale.y, zMod * 10 * scale.z);
combinedMesh.bounds = new Bounds(transform.position + size * 0.5f, size);
return combinedMesh;
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ComputeShader代码：
#pragma kernel Init #pragma kernel Emit #pragma kernel Update #include "./ComputeBuffer.cginc" RWStructuredBuffer<Particle> _Particles; int _xMod, _yMod, _zMod; float4 _Scale; float4 _Pos; float _Time; float _Speed; float _Height; float4 _LocalToWorld; inline uint Index(uint3 id) ｛ return id.x + id.y * _xMod + id.z * _xMod * _yMod; ｝ inline float Random(float2 seed) ｛ return frac(sin(dot(seed.xy, float2(12.9898, 78.233))) * 43758.5453); ｝ inline float3 Random3(float3 seed) ｛ return float3(Random(seed.yz), Random(seed.xz), Random(seed.xy)); ｝ [numthreads(10, 10, 10)] void Init(uint3 id : SV_DispatchThreadID) ｛ uint index = Index(id); Particle p = _Particles[index]; p.position = id * _Scale.xyz; p.direction = float3(0, 0, 1); p.scale = _Scale.xyz; p.uv = p.position.xy / (float2(_xMod, _yMod)*_Scale.xy); float z = p.position.z / (_zMod *_Scale.z); p.color = float4(z, z, z, 1); p.lifeTime = -Random(id.xy); _Particles[index] = p; ｝ [numthreads(10, 10, 10)] void Update(uint3 id : SV_DispatchThreadID) ｛ uint index = Index(id); Particle p = _Particles[index]; if (p.lifeTime > 0 && p.lifeTime < _Time) ｛ p.position = id * _Scale.xyz; p.lifeTime = -Random(id.xy); ｝ p.lifeTime -= _Time; if (p.lifeTime < 0) ｛ p.position += sin(p.lifeTime * 10)*float3(0, 0, 0.02f); ｝ else ｛ p.position += p.direction * _Time; ｝ _Particles[index] = p; ｝ [numthreads(10, 10, 10)] void Emit(uint3 id : SV_DispatchThreadID) ｛ uint index = Index(id); Particle p = _Particles[index]; float3 pos = id * _Scale.xyz; float dis = clamp((20 - distance(pos.xy, _Pos.xy)) / 20, 0, 1); dis = dis * dis * dis; if (dis > 0.1) ｛ float rand = Random(pos.xy); float z = 1 - pos.z / (_zMod *_Scale.z); p.position = float3(pos.x, pos.y, pos.z + z * _Height * rand * dis); p.direction = float3(0, 0, -_Height * z * rand * dis); p.lifeTime = 1; ｝ _Particles[index] = p; ｝
Shader代码：
Shader "QQ/Mesh"
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Properties
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_Color("Color",color)=(0.5,0.5,0.5,1)
_MainTex("Texture", 2D) = "white" ｛｝
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SubShader
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Tags｛ "RenderType" = "Opaque" ｝
CGINCLUDE
#pragma multi_compile_fog
#pragma target 5.0
#include "UnityCG.cginc"
#include "AutoLight.cginc"
#include "./ComputeBuffer.cginc"
uniform StructuredBuffer<Particle> _Particles;
uniform float _IdOffset;
uniform fixed4 _Color;
uniform sampler2D _MainTex;
uniform float4 _MainTex_ST;
uniform float4 _LightColor0;
inline int GetID(float2 uv)
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return (int)(uv.x + 0.5 + _IdOffset);
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ENDCG
Pass
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Tags｛"LightMode" = "Deferred"｝
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma multi_compile_shadowcaster
#pragma multi_compile ___ UNITY_HDR_ON
struct G_Buffer
｛
fixed4 diffuse : SV_Target0;
float4 specSmoothness : SV_Target1;
float4 normal : SV_Target2;
fixed4 emission : SV_Target3;
｝;
struct a2v
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float4 vertex : POSITION;
float3 normal : NORMAL;
float2 uv : TEXCOORD0;
float2 id : TEXCOORD1;
｝;
struct v2f
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float4 pos : SV_POSITION;
float3 normal : NORMAL;
float2 uv : TEXCOORD0;
float4 color : TEXCOORD1;
｝;
v2f vert(a2v v)
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Particle p = _Particles[GetID(v.id)];
v.vertex.xyz *= p.scale;
v.vertex.xyz += p.position;
v2f o;
o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
o.uv = p.uv;
o.color = p.color;
o.normal = UnityObjectToWorldNormal(v.normal);
return o;
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G_Buffer frag(v2f i)
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i.normal = normalize(i.normal);
fixed4 col = tex2D(_MainTex, i.uv)*i.color;
clip(col.a - 0.2);
G_Buffer g;
g.diffuse = _Color;
g.specSmoothness = 0;
g.normal = half4(i.normal * 0.5 + 0.5, 1);
g.emission = col;
#ifndef UNITY_HDR_ON
g.emission.rgb = exp2(-g.emission.rgb);
#endif
return g;
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ENDCG
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Pass
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Tags｛ "LightMode" = "ShadowCaster" ｝
ZWrite On
ZTest LEqual
Offset 1, 1
CGPROGRAM
#pragma vertex vert_
#pragma fragment frag_
#pragma multi_compile_shadowcaster
struct a2v_ ｛
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
float2 id : TEXCOORD1;
｝;
struct v2f_ ｛
V2F_SHADOW_CASTER;
float2 uv : TEXCOORD1;
｝;
v2f_ vert_(a2v_ v) ｛
Particle p = _Particles[GetID(v.id)];
v.vertex.xyz *= p.scale;
v.vertex.xyz += p.position;
v2f_ o;
o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
o.uv = p.uv;
TRANSFER_SHADOW_CASTER(o)
return o;
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float4 frag_(v2f_ i) : COLOR｛
float4 col = tex2D(_MainTex,i.uv);
clip(col.a - 0.2);
SHADOW_CASTER_FRAGMENT(i)
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ENDCG
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FallBack "Diffuse"
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