Unity角色残影特效

残影特效在网上有很多例子，比如这个，我参考着自己整合了一下，算是整合了一个比较完整且特别简单易用的出来，只需要一个脚本挂上去无需任何设定就能用。

这里只针对SkinnedMeshRenderer的网格（也就是带蒙皮的网格）残影，主要原理是根据设定的间隔时间连续的截取当前SkinnedMeshRenderer的网格数据并使用Graphics.DrawMesh画出网格。

一、首先是我们的残影类，为了能及时的Destroy，所以它最好派生至Object：

class AfterImage : Object
{
    //残影网格
    public Mesh _Mesh;
    //残影纹理
    public Material _Material;
    //残影位置
    public Matrix4x4 _Matrix;
    //残影透明度
    public float _Alpha;
    //残影启动时间
    public float _StartTime;
    //残影保留时间
    public float _Duration;

    public AfterImage(Mesh mesh, Material material, Matrix4x4 matrix4x4, float alpha, float startTime, float duration)
    {
        _Mesh = mesh;
        _Material = material;
        _Matrix = matrix4x4;
        _Alpha = alpha;
        _StartTime = startTime;
        _Duration = duration;
    }
}

属性描述：残影从创建之时起便记录《残影启动时间》，当其生命周期达到或者超过了设定的《残影保留时间》时，该残影即被清除；《残影网格》为残影创建之时从SkinnedMeshRenderer截取而来，保留有当前SkinnedMeshRenderer的网格数据，并依据设定的《残影纹理》在《残影位置》以《残影透明度》DrawMesh。

二、我们再定义一个残影特效类来管理残影：

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
/// <summary>
/// 残影特效
/// </summary>
public class AfterImageEffects : MonoBehaviour {

    //开启残影
    public bool _OpenAfterImage;

    //残影颜色
    public Color _AfterImageColor = Color.black;
    //残影的生存时间
    public float _SurvivalTime = 1;
    //生成残影的间隔时间
    public float _IntervalTime = 0.2f;
    private float _Time = 0;
    //残影初始透明度
    [Range(0.1f, 1.0f)]
    public float _InitialAlpha = 1.0f;

    private List<AfterImage> _AfterImageList;
    private SkinnedMeshRenderer _SkinnedMeshRenderer;

    void Awake () {
        _AfterImageList = new List<AfterImage>();
        _SkinnedMeshRenderer = GetComponent<SkinnedMeshRenderer>();
    }
    void Update () {
        if (_OpenAfterImage && _AfterImageList != null)
        {
            if (_SkinnedMeshRenderer == null)
            {
                _OpenAfterImage = false;
                return;
            }

            _Time += Time.deltaTime;
            //生成残影
            CreateAfterImage();
            //刷新残影
            UpdateAfterImage();
        }
    }
}

属性描述：《残影的生存时间》为每个残影从创建开始到销毁经历的时间，《生成残影的间隔时间》为残影创建后到下一个残影创建的时间，每个残影都会从《初始透明度》逐渐变化到0透明度并销毁。

生成残影：

/// <summary>
    /// 生成残影
    /// </summary>
    void CreateAfterImage()
    {
        //生成残影
        if (_Time >= _IntervalTime)
        {
            _Time = 0;

            Mesh mesh = new Mesh();
            _SkinnedMeshRenderer.BakeMesh(mesh);

            Material material = new Material(_SkinnedMeshRenderer.material);
            SetMaterialRenderingMode(material, RenderingMode.Fade);

            _AfterImageList.Add(new AfterImage(
                mesh,
                material,
                transform.localToWorldMatrix,
                _InitialAlpha,
                Time.realtimeSinceStartup,
                _SurvivalTime));
        }
    }

刷新残影：

/// <summary>
    /// 刷新残影
    /// </summary>
    void UpdateAfterImage()
    {
        //刷新残影，根据生存时间销毁已过时的残影
        for (int i = 0; i < _AfterImageList.Count; i++)
        {
            float _PassingTime = Time.realtimeSinceStartup - _AfterImageList[i]._StartTime;

            if (_PassingTime > _AfterImageList[i]._Duration)
            {
                _AfterImageList.Remove(_AfterImageList[i]);
                Destroy(_AfterImageList[i]);
                continue;
            }

            if (_AfterImageList[i]._Material.HasProperty("_Color"))
            {
                _AfterImageList[i]._Alpha *= (1 - _PassingTime / _AfterImageList[i]._Duration);
                _AfterImageColor.a = _AfterImageList[i]._Alpha;
                _AfterImageList[i]._Material.SetColor("_Color", _AfterImageColor);
            }

            Graphics.DrawMesh(_AfterImageList[i]._Mesh, _AfterImageList[i]._Matrix, _AfterImageList[i]._Material, gameObject.layer);
        }
    }

残影存在透明通道，所以必须要设置纹理的渲染模式为fade模式：

/// <summary>
    /// 设置纹理渲染模式
    /// </summary>
    void SetMaterialRenderingMode(Material material, RenderingMode renderingMode)
    {
        switch (renderingMode)
        {
            case RenderingMode.Opaque:
                material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.One);
                material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.Zero);
                material.SetInt("_ZWrite", 1);
                material.DisableKeyword("_ALPHATEST_ON");
                material.DisableKeyword("_ALPHABLEND_ON");
                material.DisableKeyword("_ALPHAPREMULTIPLY_ON");
                material.renderQueue = -1;
                break;
            case RenderingMode.Cutout:
                material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.One);
                material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.Zero);
                material.SetInt("_ZWrite", 1);
                material.EnableKeyword("_ALPHATEST_ON");
                material.DisableKeyword("_ALPHABLEND_ON");
                material.DisableKeyword("_ALPHAPREMULTIPLY_ON");
                material.renderQueue = 2450;
                break;
            case RenderingMode.Fade:
                material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.SrcAlpha);
                material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
                material.SetInt("_ZWrite", 0);
                material.DisableKeyword("_ALPHATEST_ON");
                material.EnableKeyword("_ALPHABLEND_ON");
                material.DisableKeyword("_ALPHAPREMULTIPLY_ON");
                material.renderQueue = 3000;
                break;
            case RenderingMode.Transparent:
                material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.One);
                material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
                material.SetInt("_ZWrite", 0);
                material.DisableKeyword("_ALPHATEST_ON");
                material.DisableKeyword("_ALPHABLEND_ON");
                material.EnableKeyword("_ALPHAPREMULTIPLY_ON");
                material.renderQueue = 3000;
                break;
        }
    }

三、效果图如下：

四、我将完整的源码贴一遍，只需要新建一个脚本AfterImageEffects，复制以下源码到其中，然后挂在有SkinnedMeshRenderer组件的模型上，并勾选OpenAfterImage，运行便可以看到效果：

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
/// <summary>
/// 残影特效
/// </summary>
public class AfterImageEffects : MonoBehaviour {

    //开启残影
    public bool _OpenAfterImage;

    //残影颜色
    public Color _AfterImageColor = Color.black;
    //残影的生存时间
    public float _SurvivalTime = 1;
    //生成残影的间隔时间
    public float _IntervalTime = 0.2f;
    private float _Time = 0;
    //残影初始透明度
    [Range(0.1f, 1.0f)]
    public float _InitialAlpha = 1.0f;

    private List<AfterImage> _AfterImageList;
    private SkinnedMeshRenderer _SkinnedMeshRenderer;

    void Awake () {
        _AfterImageList = new List<AfterImage>();
        _SkinnedMeshRenderer = GetComponent<SkinnedMeshRenderer>();
    }
	void Update () {
        if (_OpenAfterImage && _AfterImageList != null)
        {
            if (_SkinnedMeshRenderer == null)
            {
                _OpenAfterImage = false;
                return;
            }

            _Time += Time.deltaTime;
            //生成残影
            CreateAfterImage();
            //刷新残影
            UpdateAfterImage();
        }
	}
    /// <summary>
    /// 生成残影
    /// </summary>
    void CreateAfterImage()
    {
        //生成残影
        if (_Time >= _IntervalTime)
        {
            _Time = 0;

            Mesh mesh = new Mesh();
            _SkinnedMeshRenderer.BakeMesh(mesh);

            Material material = new Material(_SkinnedMeshRenderer.material);
            SetMaterialRenderingMode(material, RenderingMode.Fade);

            _AfterImageList.Add(new AfterImage(
                mesh,
                material,
                transform.localToWorldMatrix,
                _InitialAlpha,
                Time.realtimeSinceStartup,
                _SurvivalTime));
        }
    }
    /// <summary>
    /// 刷新残影
    /// </summary>
    void UpdateAfterImage()
    {
        //刷新残影，根据生存时间销毁已过时的残影
        for (int i = 0; i < _AfterImageList.Count; i++)
        {
            float _PassingTime = Time.realtimeSinceStartup - _AfterImageList[i]._StartTime;

            if (_PassingTime > _AfterImageList[i]._Duration)
            {
                _AfterImageList.Remove(_AfterImageList[i]);
                Destroy(_AfterImageList[i]);
                continue;
            }

            if (_AfterImageList[i]._Material.HasProperty("_Color"))
            {
                _AfterImageList[i]._Alpha *= (1 - _PassingTime / _AfterImageList[i]._Duration);
                _AfterImageColor.a = _AfterImageList[i]._Alpha;
                _AfterImageList[i]._Material.SetColor("_Color", _AfterImageColor);
            }

            Graphics.DrawMesh(_AfterImageList[i]._Mesh, _AfterImageList[i]._Matrix, _AfterImageList[i]._Material, gameObject.layer);
        }
    }
    /// <summary>
    /// 设置纹理渲染模式
    /// </summary>
    void SetMaterialRenderingMode(Material material, RenderingMode renderingMode)
    {
        switch (renderingMode)
        {
            case RenderingMode.Opaque:
                material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.One);
                material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.Zero);
                material.SetInt("_ZWrite", 1);
                material.DisableKeyword("_ALPHATEST_ON");
                material.DisableKeyword("_ALPHABLEND_ON");
                material.DisableKeyword("_ALPHAPREMULTIPLY_ON");
                material.renderQueue = -1;
                break;
            case RenderingMode.Cutout:
                material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.One);
                material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.Zero);
                material.SetInt("_ZWrite", 1);
                material.EnableKeyword("_ALPHATEST_ON");
                material.DisableKeyword("_ALPHABLEND_ON");
                material.DisableKeyword("_ALPHAPREMULTIPLY_ON");
                material.renderQueue = 2450;
                break;
            case RenderingMode.Fade:
                material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.SrcAlpha);
                material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
                material.SetInt("_ZWrite", 0);
                material.DisableKeyword("_ALPHATEST_ON");
                material.EnableKeyword("_ALPHABLEND_ON");
                material.DisableKeyword("_ALPHAPREMULTIPLY_ON");
                material.renderQueue = 3000;
                break;
            case RenderingMode.Transparent:
                material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.One);
                material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
                material.SetInt("_ZWrite", 0);
                material.DisableKeyword("_ALPHATEST_ON");
                material.DisableKeyword("_ALPHABLEND_ON");
                material.EnableKeyword("_ALPHAPREMULTIPLY_ON");
                material.renderQueue = 3000;
                break;
        }
    }
}
public enum RenderingMode
{
    Opaque,
    Cutout,
    Fade,
    Transparent,
}
class AfterImage : Object
{
    //残影网格
    public Mesh _Mesh;
    //残影纹理
    public Material _Material;
    //残影位置
    public Matrix4x4 _Matrix;
    //残影透明度
    public float _Alpha;
    //残影启动时间
    public float _StartTime;
    //残影保留时间
    public float _Duration;

    public AfterImage(Mesh mesh, Material material, Matrix4x4 matrix4x4, float alpha, float startTime, float duration)
    {
        _Mesh = mesh;
        _Material = material;
        _Matrix = matrix4x4;
        _Alpha = alpha;
        _StartTime = startTime;
        _Duration = duration;
    }
}