unity URP 利用particle system制作简单的shader交互

首先这里制作了一个简单交互，使用shader grapgh，根据计算距离和变化数值的差实现交互后的扩散，同时计算消散遮罩让它逐渐谈去。

将他赋予材质物体，根据脚本传入位置和逐渐变化的大小后，呈现这样的效果。

但是，shader graph这样的工具，在做这种效果非常快的同时，也存在不少缺点，比如这里我希望我传入的位置和大小变化都是数组，使用shader graph就不太好办了。

这时候就需要把它翻译成代码，根据连线图的逻辑翻译即可，此外把传入的位置和size值替换为数组。

Shader "yourname"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _HitPos("HitPos", Vector) = (0, 0, 0, 0)
        _HitSize("HitSize", Float) = 0.001
        _HitSpread("HitSpread", Range(0, 10)) = 1
        _HitSizeMax("HitSizeMax", Float) = 0
        _DisappearSpread("DisappearSpread", Float) = 1
        _HitSpreadNoiseMulti("HitSpreadNoiseMulti", Range(0.01, 10)) = 1
        _HitSpreadNoiseScale("HitSpreadNoiseScale", Range(1, 200)) = 20
        [HideInInspector]_QueueOffset("_QueueOffset", Float) = 0
        [HideInInspector]_QueueControl("_QueueControl", Float) = -1
        [HideInInspector][NoScaleOffset]unity_Lightmaps("unity_Lightmaps", 2DArray) = "" {}
        [HideInInspector][NoScaleOffset]unity_LightmapsInd("unity_LightmapsInd", 2DArray) = "" {}
        [HideInInspector][NoScaleOffset]unity_ShadowMasks("unity_ShadowMasks", 2DArray) = "" {}


    }
    SubShader
    {

        Tags
        {
            "RenderPipeline"="UniversalPipeline"
            "RenderType"="Opaque"
            //"UniversalMaterialType" = "Lit"
            "Queue"="Geometry"
            "DisableBatching"="False"
        }

        Pass
        {

            Name "Universal Forward"
            Tags
            {
                "LightMode" = "UniversalForward"
            }
            Cull Back
            Blend One Zero
            ZTest LEqual
            ZWrite On
           
            HLSLPROGRAM
            #pragma enable_d3d11_debug_symbols  //  debug信息
            #pragma multi_compile_instancing
            #pragma target 4.0  // 默认2.5 target的详细信息 https://docs.unity3d.com/Manual/SL-ShaderCompileTargets.html
   
            #pragma vertex vert
         
            #pragma fragment frag
         
            //https://github.com/Unity-Technologies/Graphics/tree/master/Packages/com.unity.render-pipelines.universal/ShaderLibrary
            #include_with_pragmas "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DOTS.hlsl"
            #include_with_pragmas "Packages/com.unity.render-pipelines.universal/ShaderLibrary/RenderingLayers.hlsl"
            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"
            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Texture.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Input.hlsl"
            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/TextureStack.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Shadows.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/ShaderGraphFunctions.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DBuffer.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/Editor/ShaderGraph/Includes/ShaderPass.hlsl"
            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Hashes.hlsl"

      

            float Unity_SimpleNoise_ValueNoise_Deterministic_float (float2 uv)
            {
                float2 i = floor(uv);
                float2 f = frac(uv);
                f = f * f * (3.0 - 2.0 * f);
                uv = abs(frac(uv) - 0.5);
                float2 c0 = i + float2(0.0, 0.0);
                float2 c1 = i + float2(1.0, 0.0);
                float2 c2 = i + float2(0.0, 1.0);
                float2 c3 = i + float2(1.0, 1.0);
                float r0; Hash_Tchou_2_1_float(c0, r0);
                float r1; Hash_Tchou_2_1_float(c1, r1);
                float r2; Hash_Tchou_2_1_float(c2, r2);
                float r3; Hash_Tchou_2_1_float(c3, r3);
                float bottomOfGrid = lerp(r0, r1, f.x);
                float topOfGrid = lerp(r2, r3, f.x);
                float t = lerp(bottomOfGrid, topOfGrid, f.y);
                return t;
            }
        
            void Unity_SimpleNoise_Deterministic_float(float2 UV, float Scale, out float Out)
            {
                float freq, amp;
                Out = 0.0f;
                freq = pow(2.0, float(0));
                amp = pow(0.5, float(3-0));
                Out += Unity_SimpleNoise_ValueNoise_Deterministic_float(float2(UV.xy*(Scale/freq)))*amp;
                freq = pow(2.0, float(1));
                amp = pow(0.5, float(3-1));
                Out += Unity_SimpleNoise_ValueNoise_Deterministic_float(float2(UV.xy*(Scale/freq)))*amp;
                freq = pow(2.0, float(2));
                amp = pow(0.5, float(3-2));
                Out += Unity_SimpleNoise_ValueNoise_Deterministic_float(float2(UV.xy*(Scale/freq)))*amp;
            }

            void Unity_SampleGradientV1_float(Gradient Gradient, float Time, out float4 Out)
            {
                float3 color = Gradient.colors[0].rgb;
                [unroll]
                for (int c = 1; c < Gradient.colorsLength; c++)
                {
                    float colorPos = saturate((Time - Gradient.colors[c - 1].w) / (Gradient.colors[c].w - Gradient.colors[c - 1].w)) * step(c, Gradient.colorsLength - 1);
                    color = lerp(color, Gradient.colors[c].rgb, lerp(colorPos, step(0.01, colorPos), Gradient.type));
                }
            #ifdef UNITY_COLORSPACE_GAMMA
                color = LinearToSRGB(color);
            #endif
                float alpha = Gradient.alphas[0].x;
                [unroll]
                for (int a = 1; a < Gradient.alphasLength; a++)
                {
                    float alphaPos = saturate((Time - Gradient.alphas[a - 1].y) / (Gradient.alphas[a].y - Gradient.alphas[a - 1].y)) * step(a, Gradient.alphasLength - 1);
                    alpha = lerp(alpha, Gradient.alphas[a].x, lerp(alphaPos, step(0.01, alphaPos), Gradient.type));
                }
                Out = float4(color, alpha);
            }

            struct appdata
            {
                //顶点着色器语义 https://learn.microsoft.com/zh-cn/windows/win32/direct3dhlsl/dx-graphics-hlsl-semantics?redirectedfrom=MSDN
                float4 vertex : POSITION;
                float3  normal  : NORMAL;
                float4  tan  : TANGENT;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                //像素着色器语义 https://learn.microsoft.com/zh-cn/windows/win32/direct3dhlsl/dx-graphics-hlsl-semantics?redirectedfrom=MSDN
                float4 positionCS : SV_POSITION;
                float3  normal  : NORMAL;
                float2 uv : TEXCOORD0;
                float3 positionWS : TEXCOORD1;
            };
            //从片段着色器的返回结构，SV_Target,SV_Depth等,不知道这两个之外还有能用的不。SV_Target可以从0到7，在多渲染目标(MRT)时很有用
            struct fragOutput {
                //语义 https://learn.microsoft.com/zh-cn/windows/win32/direct3dhlsl/dx-graphics-hlsl-semantics?redirectedfrom=MSDN
                float4 Emission : SV_Target;
            };


            sampler2D _MainTex;
            float4 _MainTex_ST; 

            float _HitSpreadNoiseScale;
            float _HitSpreadNoiseMulti;
            int count;
            float3 hitposarray[20];
            float hitsizearray[20];
            float hitspreadarray[20];
            float hitsizemaxarray[20];
            float disappearspreadarray[20];


            v2f vert(appdata v, uint vid : SV_VertexID)
            {
                v2f o;
                o.positionCS = TransformObjectToHClip(v.vertex);
                o.positionWS = TransformObjectToWorld(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.normal = v.normal;
                return o;
            }

            float4 CalculateCircle(v2f i, float3 _HitPos, float _HitSize, float _HitSpread, float _HitSizeMax, float _DisappearSpread)
            {
                float3 tempdis = distance(_HitPos, i.positionWS);
                float tempupmul = clamp(((tempdis - _HitSizeMax) * (-1) )/ _DisappearSpread, 0, 1);

                float noiseout = 0;
                Unity_SimpleNoise_Deterministic_float(i.uv, _HitSpreadNoiseScale, noiseout);
                noiseout = noiseout * _HitSpreadNoiseMulti;
                float temp1 = noiseout + (tempdis - _HitSize);
                float temp2 = 1 - clamp(temp1 / min(_HitSize, _HitSpread), 0, 1);
                Gradient _Gradient = NewGradient(0, 4, 2, float4(0, 0, 0, 0),float4(0.767647, 0.767647, 0.767647, 0.1058824),float4(0.6861503, 0.6861503, 0.6861503, 0.7705958),float4(0, 0, 0, 0.9647059),float4(0, 0, 0, 0),float4(0, 0, 0, 0),float4(0, 0, 0, 0),float4(0, 0, 0, 0), float2(1, 0),float2(1, 1),float2(0, 0),float2(0, 0),float2(0, 0),float2(0, 0),float2(0, 0),float2(0, 0));
                float4 gradientout = 0;
                Unity_SampleGradientV1_float(_Gradient, temp2, gradientout);

                return tempupmul * gradientout;
            }

            fragOutput frag(v2f i) : SV_Target
            {
                fragOutput o = (fragOutput)0;
                float4 tempemission = 0;
                for(int j = 0; j < count; j++){
                    tempemission += CalculateCircle(i, hitposarray[j], hitsizearray[j], hitspreadarray[j], hitsizemaxarray[j], disappearspreadarray[j]);
                };
                o.Emission = tempemission;


                return o;
            }
            ENDHLSL
        }
    }
    Fallback Off
}

particle system制作为在点击位置射线检测，生成粒子，并逐渐放大，最后消失。

弄好后关闭粒子的renderer，使其不可见。

然后创建脚本根据particle system产生的粒子位置和大小，particle system，按个数传入shader代码的数组中，按照粒子的位置和大小同步shader数组中的值以实现效果。

using System.Collections;
using System.Collections.Generic;
using Unity.Mathematics;
using UnityEngine;
using UnityEngine.InputSystem;
using static UnityEngine.Rendering.DebugUI;

[ExecuteAlways]
public class ForceField : MonoBehaviour
{
    //编辑器引用
    public GameObject forcefield;
    public ParticleSystem ps;
    //静态存储
    [Header("粒子系统最大数量")]
    public int psAmount = 20;
    Material material;
    Shader shader;
    Mouse mouse;
    //动态变化存储
    RaycastHit raycastHit;
    ParticleSystem.Particle[] particles;
    bool isInited = false;

    void Init()
    {
        if (material == null)
            material = forcefield.GetComponent<MeshRenderer>().sharedMaterial;
        if (shader == null)
            shader = material.shader;
        if (mouse == null)
            mouse = Mouse.current;

        particles = new ParticleSystem.Particle[psAmount];
    }

    void Update()
    {
        //编辑器模式下就要做的事情
        if (forcefield == null) return;
        if (ps == null) return;

        if (!isInited)
        {
            Init();
            isInited = true;
        }

        //运行模式下才要做的事情
        if (!Application.isPlaying) return;
        if (mouse.leftButton.wasPressedThisFrame)//Status:鼠标左键按下  运行时才有作用
        {
            Vector2 mousePos = Pointer.current.position.ReadValue();
            Ray ray = Camera.main.ScreenPointToRay(mousePos);
            Physics.Raycast(ray, out raycastHit, 1000, LayerMask.GetMask("ForceField"));
            
            if(raycastHit.collider != null)//检测有效，做以下操作
            {
                ps.transform.position = raycastHit.point;
                ps.Emit(1);
            }
        }

        ParticleSystem.MainModule psMainModule = ps.main;
        int count = ps.GetParticles(particles);
        Debug.Log(count);

        material.SetInteger("count", count);  //  激活的个数

        if(count > 0)
        {
            Vector4[] hitposs = new Vector4[20];
            float[] hitsizes = new float[20];
            float[] hitspreads = new float[20];
            float[] hitsizemaxs = new float[20];
            float[] disappearspreads = new float[20];
            for (int i = 0; i < count; i++)
            {
                hitposs[i] = new Vector4(particles[i].position.x, particles[i].position.y, particles[i].position.z, 1);
                hitsizes[i] = particles[i].GetCurrentSize(ps);
                hitspreads[i] = 1;
                hitsizemaxs[i] = psMainModule.startSize.constantMax;
                disappearspreads[i] = psMainModule.startSize.constantMax / 2;
            }
            material.SetVectorArray("hitposarray", hitposs);
            material.SetFloatArray("hitsizearray", hitsizes);
            material.SetFloatArray("hitspreadarray", hitspreads);
            material.SetFloatArray("hitsizemaxarray", hitsizemaxs);
            material.SetFloatArray("disappearspreadarray", disappearspreads);
        }

    }

}

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