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unity用ComputeShader做模型流体喷涂喷绘工具

左右... 2024-06-17 10:14:31

简介unity用ComputeShader做模型流体喷涂喷绘工具

最近在研究喷涂喷绘项目，需要做大量纹理图形运算，因此更适合用GPU来处理，在unity中用ComputeShader完成像素运算，SurfaceShader完成纹理渲染。

实现思路：

1.用射线碰撞模型，得到碰撞纹理坐标brushX和brushY

2.ComputeShader拿到brush坐标，在纹理相应的位置做像素运算，并输出纹理ComputeTexture

3.通过SurfaceShader渲染纹理

管理代码：

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEditor.VersionControl;
using UnityEngine;
using UnityEngine.UI;

namespace Game.Patinter
{
    public class PatintManager : MonoBehaviour
    {
        //图片尺寸
        public static int textureSize = 1024;

        //渲染模型
        public GameObject paintSurfacePanel;
        
        //渲染模型
        public GameObject paintDataPanel;

        //运算shader
        private ComputeShader computeShader;
        
        //运算纹理
        private RenderTexture computeTexture;
        
        //输出纹理
        private Texture2D resultTexture;
        
        private int computeShaderKernel;
        
        // Start is called before the first frame update
        void Start()
        {
            //实例化shader
            computeShader = (ComputeShader) Resources.Load("Shader/PaintComputeShader", typeof(ComputeShader));
            computeShaderKernel = computeShader.FindKernel("PaintCompute");

            //创建纹理
            computeTexture = new RenderTexture(textureSize, textureSize, 24);
            computeTexture.enableRandomWrite = true;
            computeTexture.Create();

            //绑定纹理
            computeShader.SetTexture(computeShaderKernel, "paintTexture", computeTexture);
            computeShader.SetInt("textureSize", textureSize);
            
            //输出纹理
            resultTexture = new Texture2D(textureSize, textureSize, TextureFormat.ARGB32, false);
        }

        // Update is called once per frame
        void Update()
        {
            //鼠标左键按下开始喷绘
            if (Input.GetMouseButton(0))
            {
                var ray = Camera.main.ScreenPointToRay(Input.mousePosition);
                RaycastHit hit;
                Physics.Raycast(ray, out hit, 100);
                
                //检测到碰撞体
                if (hit.collider != null)
                {
                    var hitX = hit.textureCoord.x;
                    var hitY = hit.textureCoord.y;
                    
                    Render(hitX, hitY);
                    return;
                }
                
                //未检测到碰撞体
                Render(0, 0);
            }
            else
            {
                Render(0, 0);
            }
            
            //空格清空面板
            if (Input.GetKeyDown(KeyCode.Space))
            {
                computeTexture = new RenderTexture(textureSize, textureSize, 24);
                computeTexture.enableRandomWrite = true;
                computeTexture.Create();

                computeShader.SetTexture(computeShaderKernel, "paintTexture", computeTexture);

                Render(0, 0);
            }
        }

        void Render(float hitX, float hitY)
        {
            //传入绘制点
            computeShader.SetFloat("brushX", hitX * textureSize);
            computeShader.SetFloat("brushY", hitY * textureSize);
            
            //纹理运算
            computeShader.Dispatch(computeShaderKernel, textureSize / 8, textureSize / 8, 1);

            //拷贝纹理
            RenderTexture.active = computeTexture;
            resultTexture.ReadPixels(new Rect(0, 0, textureSize, textureSize), 0, 0);
            resultTexture.Apply();

            //渲染纹理
            paintDataPanel.GetComponent<MeshRenderer>().material.SetTexture("_MainTex", resultTexture);
            paintSurfacePanel.GetComponent<MeshRenderer>().material.SetTexture("_PaintDataTex", resultTexture);
        }
    }
}

代码很简单，就80行；在Start中初始化；Update中检测射线实时渲染；Render负责传入参数启动运算。

ComputeShader:

// Each #kernel tells which function to compile; you can have many kernels
#pragma kernel PaintCompute

// Create a RenderTexture with enableRandomWrite flag and set it
// with cs.SetTexture
RWTexture2D<float4> paintTexture;

float brushX;
float brushY;

int textureSize;

[numthreads(8,8,1)]
void PaintCompute(uint3 id : SV_DispatchThreadID)
{
    //绘制点有效
    if (brushX != 0 && brushY != 0)
    {
        // TODO: insert actual code here!
        //和绘制点距离
        float dis = distance(id.xy, float2(brushX, brushY));

        //距离小于90个像素
        if (dis < 90)
        {
            float4 v = paintTexture[id.xy];

            //添加边缘模糊
            float rate = 1 - dis / 90;
            v.x += 0.04 * rate;
            
            paintTexture[id.xy] = v;
        }
    }

    //流体效果
    if (id.y > 0)
    {
        float4 v = paintTexture[id.xy];

        //大于0.9向下流动
        if (v.x > 0.9)
        {
            v.x -= 0.02f;
            paintTexture[id.xy] = v;
            
            float4 down = paintTexture[id.xy - float2(0, 1)];
            if (down.x < 0.8f)down.x = 0.8;
            down += float4(0.0178f, 0, 0, 0);
            
            paintTexture[id.xy - float2(0, 1)] = down;
        }
    }
}

为了更像喷绘的效果，需要加上边缘模糊和流体效果

模型shader：

Shader "Custom/PaintSurfaceShader"
{
    Properties
    {
        _Color ("Color", Color) = (1,1,1,1)
        _MainTex ("Albedo (RGB)", 2D) = "white" {}
        _PaintDataTex ("PaintDataTex (RGB)", 2D) = "black" {}
        _Glossiness ("Smoothness", Range(0,1)) = 0.5
        _Metallic ("Metallic", Range(0,1)) = 0.0
    }
    SubShader
    {
        Tags
        {
            "RenderType"="Opaque"
        }
        LOD 200

        CGPROGRAM
        // Physically based Standard lighting model, and enable shadows on all light types
        #pragma surface surf Standard fullforwardshadows

        // Use shader model 3.0 target, to get nicer looking lighting
        #pragma target 3.0

        sampler2D _MainTex;
        sampler2D _PaintDataTex;

        struct Input
        {
            float2 uv_MainTex;
            float3 worldRefl;
            INTERNAL_DATA
        };

        half _Glossiness;
        half _Metallic;
        fixed4 _Color;

        // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
        // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
        // #pragma instancing_options assumeuniformscaling
        UNITY_INSTANCING_BUFFER_START(Props)
        // put more per-instance properties here
        UNITY_INSTANCING_BUFFER_END(Props)

        void surf(Input IN, inout SurfaceOutputStandard o)
        {
            // Albedo comes from a texture tinted by color
            fixed4 c = tex2D(_MainTex, IN.uv_MainTex);
            fixed4 p = tex2D(_PaintDataTex, IN.uv_MainTex);

            o.Albedo = c.rgb * (1 - p.r) + _Color * p.r;

            // Metallic and smoothness come from slider variables
            o.Metallic = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha = c.a;
        }
        ENDCG
    }
    FallBack "Diffuse"
}

将模型本身的纹理和喷涂上色混合

热力图Shader：

Shader "Custom/PaintDataShader"
{
    Properties
    {
        _Color ("Color", Color) = (1,1,1,1)
        _MainTex ("Albedo (RGB)", 2D) = "black" {}
        _ColorMapTex ("ColorMap (RGB)", 2D) = "black" {}
        _Glossiness ("Smoothness", Range(0,1)) = 0.5
        _Metallic ("Metallic", Range(0,1)) = 0.0
    }
    SubShader
    {
        Tags
        {
            "RenderType"="Opaque"
        }
        LOD 200

        CGPROGRAM
        // Physically based Standard lighting model, and enable shadows on all light types
        #pragma surface surf Standard fullforwardshadows

        // Use shader model 3.0 target, to get nicer looking lighting
        #pragma target 3.0

        sampler2D _MainTex;
        sampler2D _ColorMapTex;

        struct Input
        {
            float2 uv_MainTex;
            float3 worldPos;
        };

        half _Glossiness;
        half _Metallic;
        fixed4 _Color;

        // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
        // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
        // #pragma instancing_options assumeuniformscaling
        UNITY_INSTANCING_BUFFER_START(Props)
        // put more per-instance properties here
        UNITY_INSTANCING_BUFFER_END(Props)

        void surf(Input IN, inout SurfaceOutputStandard o)
        {
            // Albedo comes from a texture tinted by color
            fixed4 c = tex2D(_MainTex, IN.uv_MainTex);
            fixed4 m = tex2D(_ColorMapTex, float2((1 - c.r)*0.9 + 0.09, 0.1));
            o.Albedo = m.rgb;

            // Metallic and smoothness come from slider variables
            o.Metallic = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha = c.a;
        }
        ENDCG
    }
    FallBack "Diffuse"
}

此功能是为了反映喷涂渲染状况

效果：