Unity 實時陰影新方案

大家都知道，實時光產生陰影的性能開銷很大，爲了在移動端有更好的性能表現，所以在網上參考了一些方案，總結了一個陰影shader去解決實時光性能開銷過大的問題。

1.陰影shader，產生陰影的物體需要使用這個shader

Shader "Custom/PlayerShadow"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
		_ShadowInvLen ("ShadowInvLen", float) = 1.0 //0.4449261
		_Power("Power", Range(0,2)) = 1.7
		_Alpha("Alpha",Range(0,1)) = 1.0
	}

	SubShader
	{
		Tags{ "RenderType" = "Opaque" "Queue" = "Geometry+10" }
		LOD 100

		Pass
		{
			CGPROGRAM

			#pragma vertex vert
			#pragma fragment frag
			// make fog work
			#pragma multi_compile_fog

			#include "UnityCG.cginc"

			struct appdata
			{
				float4 vertex : POSITION;
				float2 uv : TEXCOORD0;
			};

			struct v2f
			{
				float2 uv : TEXCOORD0;
				UNITY_FOG_COORDS(1)
				float4 vertex : SV_POSITION;
			};

			sampler2D _MainTex;
			float4 _MainTex_ST;
			fixed _Power;
			
			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
				UNITY_TRANSFER_FOG(o,o.vertex);
				return o;
			}

			fixed4 frag (v2f i) : SV_Target
			{
				// sample the texture
				fixed4 col = tex2D(_MainTex, i.uv) * _Power;

				// apply fog
				UNITY_APPLY_FOG(i.fogCoord, col);
				return col;
			}

			ENDCG
		}

		Pass
		{
			Blend SrcAlpha  OneMinusSrcAlpha
			ZWrite Off
			Cull Back
			ColorMask RGB

			Stencil
			{
				Ref 0
				Comp Equal
				WriteMask 255
				ReadMask 255
				//Pass IncrSat
				Pass Invert
				Fail Keep
				ZFail Keep
			}

			CGPROGRAM

			#pragma vertex vert
			#pragma fragment frag

			float4 _ShadowPlane; //渲染的地面
			float4 _ShadowProjDir; //渲染的光源點，這裏只是記錄點的位置，用於計算陰影的投影
			float4 _WorldPos;
			float _ShadowInvLen; //陰影的長度
			float4 _ShadowFadeParams; //陰影漸變的參數
			float _Alpha;
			struct appdata
			{
				float4 vertex : POSITION;
			};

			struct v2f
			{
				float4 vertex : SV_POSITION;
				float3 xlv_TEXCOORD0 : TEXCOORD0;
				float3 xlv_TEXCOORD1 : TEXCOORD1;
			};

			v2f vert(appdata v)
			{
				v2f o;

				float3 lightdir = normalize(_ShadowProjDir); //單位化光照方向向量
				float3 worldpos = mul(unity_ObjectToWorld, v.vertex).xyz; //模型座標轉成世界座標
				// _ShadowPlane.w = p0 * n  // 平面的w分量就是p0 * n
				float distance = (_ShadowPlane.w - dot(_ShadowPlane.xyz, worldpos)) / dot(_ShadowPlane.xyz, lightdir.xyz); //計算陰影的長度
				worldpos = worldpos + distance * lightdir.xyz; //影子的投影點
				o.vertex = mul(unity_MatrixVP, float4(worldpos, 1.0));
				o.xlv_TEXCOORD0 = _WorldPos.xyz;
				o.xlv_TEXCOORD1 = worldpos;  //影子投影的點組成的紋理
				return o;
			}

			float4 frag(v2f i) : SV_Target
			{
				float3 posToPlane_2 = (i.xlv_TEXCOORD0 - i.xlv_TEXCOORD1);
				float4 color;
				color.xyz = float3(0.0, 0.0, 0.0);
				color.w = (pow((1.0 - clamp(((sqrt(dot(posToPlane_2, posToPlane_2)) * _ShadowInvLen) - _ShadowFadeParams.x), 0.0, 1.0)), _ShadowFadeParams.y) * _ShadowFadeParams.z);  //透明度漸變計算
				color.a = color.a*_Alpha;
				return color;
			}

			ENDCG
		}
	}
}

2.控制腳本，通過獲取場景中的所有運用了陰影shader的材質。需要給定一個光源位置（空物體即可，不需要light），需要一個正交相機（不是你的主相機）

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Qarth;
using System;

namespace GameWish.Game
{
    public class ShadowController : TMonoSingleton<ShadowController>
    {
        [SerializeField]
        private Camera m_ShadowCam;//陰影渲染相機的位置
        [SerializeField]
        private GameObject m_Light;//模擬光源的位置
        [SerializeField]
        private List<Material> m_LstMat = new List<Material>();

        private void Awake()
        {
            RefreshRender();
            EventSystem.S.Register(EventID.OnMeshChange, OnMeshChange);
        }

        private void OnMeshChange(int key, object[] param)
        {
            RefreshRender();
        }

        private void RefreshRender()
        {
            m_LstMat.Clear();
            MeshRenderer[] renderlist = GetComponentsInChildren<MeshRenderer>();
            foreach (var render in renderlist)
            {
                if (render == null)
                    continue;
                foreach (var mt in render.materials)
                {
                    if (mt.shader.name == "Custom/PlayerShadow")
                        m_LstMat.Add(mt);
                }
            }
        }

        void Update()
        {
            UpdateShader();
        }

        private void UpdateShader()
        {
            if (m_Light == null)
                return;

            foreach (var mat in m_LstMat)
            {
                if (mat == null)
                    continue;
                mat.SetVector("_WorldPos", transform.position);
                mat.SetVector("_ShadowProjDir", m_Light.transform.forward);
                mat.SetVector("_ShadowPlane", new Vector4(0f, 0.4f, 0.0f, 0.0f));
                mat.SetVector("_ShadowFadeParams", new Vector4(1f, 0.9f, 0.8f, 0.7f));
            }
        }
    }

}

有問題歡迎大家提出~  參考文獻：https://blog.csdn.net/dingxiaowei2013/article/details/84237331