【Shader】基于噪声图片的动态雾效

using UnityEngine;
using System.Collections;

[ExecuteInEditMode]
[RequireComponent (typeof(Camera))]
public class PostEffectsBase : MonoBehaviour {

    protected void Start() {
        CheckResources();
    }
    // Called when start
    protected void CheckResources() {
        bool isSupported = CheckSupport();

        if (isSupported == false) {
            NotSupported();
        }
    }

    // Called in CheckResources to check support on this platform
    protected bool CheckSupport() {
        if (SystemInfo.supportsImageEffects == false || SystemInfo.supportsRenderTextures == false) {
            Debug.LogWarning("This platform does not support image effects or render textures.");
            return false;
        }

        return true;
    }

    // Called when the platform doesn't support this effect
    protected void NotSupported() {
        enabled = false;
    }



    // Called when need to create the material used by this effect
    protected Material CheckShaderAndCreateMaterial(Shader shader, Material material) {
        if (shader == null) {
            return null;
        }

        if (shader.isSupported && material && material.shader == shader)
            return material;

        if (!shader.isSupported) {
            return null;
        }
        else {
            material = new Material(shader);
            material.hideFlags = HideFlags.DontSave;
            if (material)
                return material;
            else 
                return null;
        }
    }
}

using UnityEngine;
using System.Collections;

public class FogWithNoise : PostEffectsBase {

    public Shader fogShader;
    private Material fogMaterial = null;

    public Material material {  
        get {
            fogMaterial = CheckShaderAndCreateMaterial(fogShader, fogMaterial);
            return fogMaterial;
        }  
    }

    private Camera myCamera;
    public Camera camera {
        get {
            if (myCamera == null) {
                myCamera = GetComponent<Camera>();
            }
            return myCamera;
        }
    }

    private Transform myCameraTransform;
    public Transform cameraTransform {
        get {
            if (myCameraTransform == null) {
                myCameraTransform = camera.transform;
            }

            return myCameraTransform;
        }
    }

    [Range(0.1f, 3.0f)]
    public float fogDensity = 1.0f;

    public Color fogColor = Color.white;

    public float fogStart = 0.0f;
    public float fogEnd = 2.0f;

    public Texture noiseTexture;

    [Range(-0.5f, 0.5f)]
    public float fogXSpeed = 0.1f;

    [Range(-0.5f, 0.5f)]
    public float fogYSpeed = 0.1f;

    [Range(0.0f, 3.0f)]
    public float noiseAmount = 1.0f;

    void OnEnable() {
        GetComponent<Camera>().depthTextureMode |= DepthTextureMode.Depth;
    }

    void OnRenderImage (RenderTexture src, RenderTexture dest) {
        if (material != null) {
            Matrix4x4 frustumCorners = Matrix4x4.identity;

            float fov = camera.fieldOfView;
            float near = camera.nearClipPlane;
            float aspect = camera.aspect;

            float halfHeight = near * Mathf.Tan(fov * 0.5f * Mathf.Deg2Rad);
            Vector3 toRight = cameraTransform.right * halfHeight * aspect;
            Vector3 toTop = cameraTransform.up * halfHeight;

            Vector3 topLeft = cameraTransform.forward * near + toTop - toRight;
            float scale = topLeft.magnitude / near;

            topLeft.Normalize();
            topLeft *= scale;

            Vector3 topRight = cameraTransform.forward * near + toRight + toTop;
            topRight.Normalize();
            topRight *= scale;

            Vector3 bottomLeft = cameraTransform.forward * near - toTop - toRight;
            bottomLeft.Normalize();
            bottomLeft *= scale;

            Vector3 bottomRight = cameraTransform.forward * near + toRight - toTop;
            bottomRight.Normalize();
            bottomRight *= scale;

            frustumCorners.SetRow(0, bottomLeft);
            frustumCorners.SetRow(1, bottomRight);
            frustumCorners.SetRow(2, topRight);
            frustumCorners.SetRow(3, topLeft);

            material.SetMatrix("_FrustumCornersRay", frustumCorners);

            material.SetFloat("_FogDensity", fogDensity);
            material.SetColor("_FogColor", fogColor);
            material.SetFloat("_FogStart", fogStart);
            material.SetFloat("_FogEnd", fogEnd);

            material.SetTexture("_NoiseTex", noiseTexture);
            material.SetFloat("_FogXSpeed", fogXSpeed);
            material.SetFloat("_FogYSpeed", fogYSpeed);
            material.SetFloat("_NoiseAmount", noiseAmount);

            Graphics.Blit (src, dest, material);
        } else {
            Graphics.Blit(src, dest);
        }
    }
}

Shader "Fog With Noise" {
    Properties {
        _MainTex ("Base (RGB)", 2D) = "white" {}
        _FogDensity ("Fog Density", Float) = 1.0
        _FogColor ("Fog Color", Color) = (1, 1, 1, 1)
        _FogStart ("Fog Start", Float) = 0.0
        _FogEnd ("Fog End", Float) = 1.0
        _NoiseTex ("Noise Texture", 2D) = "white" {}
        _FogXSpeed ("Fog Horizontal Speed", Float) = 0.1
        _FogYSpeed ("Fog Vertical Speed", Float) = 0.1
        _NoiseAmount ("Noise Amount", Float) = 1
    }
    SubShader {
        CGINCLUDE

        #include "UnityCG.cginc"

        float4x4 _FrustumCornersRay;

        sampler2D _MainTex;
        half4 _MainTex_TexelSize;
        sampler2D _CameraDepthTexture;
        half _FogDensity;
        fixed4 _FogColor;
        float _FogStart;
        float _FogEnd;
        sampler2D _NoiseTex;
        half _FogXSpeed;
        half _FogYSpeed;
        half _NoiseAmount;

        struct v2f {
            float4 pos : SV_POSITION;
            float2 uv : TEXCOORD0;
            float2 uv_depth : TEXCOORD1;
            float4 interpolatedRay : TEXCOORD2;
        };

        v2f vert(appdata_img v) {
            v2f o;
            o.pos = mul(UNITY_MATRIX_MVP, v.vertex);

            o.uv = v.texcoord;
            o.uv_depth = v.texcoord;

            // unity左下角0,0 右上角1,1
            //判断是否是directx平台，如果开启了抗锯齿，如果此时使用了渲染到纹理技术
            //那么此时纹理不会翻转，在顶点着色器中加入这样的处理
            #if UNITY_UV_STARTS_AT_TOP
            if (_MainTex_TexelSize.y < 0)
                o.uv_depth.y = 1 - o.uv_depth.y;
            #endif

            // 4 3
            // 1 2
            int index = 0;
            if (v.texcoord.x < 0.5 && v.texcoord.y < 0.5) {
                index = 0;
            } else if (v.texcoord.x > 0.5 && v.texcoord.y < 0.5) {
                index = 1;
            } else if (v.texcoord.x > 0.5 && v.texcoord.y > 0.5) {
                index = 2;
            } else {
                index = 3;
            }
            #if UNITY_UV_STARTS_AT_TOP
            if (_MainTex_TexelSize.y < 0)
                index = 3 - index;
            #endif

            o.interpolatedRay = _FrustumCornersRay[index];

            return o;
        }

        fixed4 frag(v2f i) : SV_Target {
            // LinearEyeDepth：视角空间下的线性深度值，
            // SAMPLE_DEPTH_TEXTURE：深度纹理采样
            float linearDepth = LinearEyeDepth(SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, i.uv_depth));
            // 1.摄像机在世界空间中的位置
            // 2.空间世界下该像素相对于摄像机的偏移量，把他们相加，得到的就是该像素的世界坐标
            float3 worldPos = _WorldSpaceCameraPos + linearDepth * i.interpolatedRay.xyz;


            float2 speed = _Time.y * float2(_FogXSpeed, _FogYSpeed);
            float noise = (tex2D(_NoiseTex, i.uv + speed).r - 0.5) * _NoiseAmount;

            float fogDensity = (_FogEnd - worldPos.y) / (_FogEnd - _FogStart); 
            fogDensity = saturate(fogDensity * _FogDensity * (1 + noise));

            fixed4 finalColor = tex2D(_MainTex, i.uv);
            finalColor.rgb = lerp(finalColor.rgb, _FogColor.rgb, fogDensity);

            return finalColor;
        }

        ENDCG

        Pass {              
            CGPROGRAM  

            #pragma vertex vert  
            #pragma fragment frag  

            ENDCG
        }
    } 
    FallBack Off
}