Unity shadow map

参考：
http://fabiensanglard.net/shadowmapping/index.php
https://learnopengl-cn.readthedocs.io/zh/latest/05 Advanced Lighting/03 Shadows/01 Shadow Mapping/
https://www.jianshu.com/p/17ccdd7c0888

不知为啥直接照抄代码实现不了 我用到unity版本是2018.4.1 不知道是不是版本的问题
先上个图吧

更具自己的理解加网上的代码，差不多是这种效果

生成深度图
存下深度数据

Shader "Shadow/DeapthTextureShader"
{
    SubShader
    {
        Tags { "RenderType"="Opaque" }

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float2 depth : TEXCOORD1;
            };
            
             v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                // o.depth = o.vertex.zw;
                o.depth = COMPUTE_DEPTH_01;
                return o;
            }
            
            fixed4 frag (v2f i) : SV_Target
            {
                // float depth = i.depth.x / i.depth.y;
                float depth = i.depth;
                // fixed4 col = EncodeFloatRGBA(depth);
                fixed4 col = EncodeFloatRGBA(min(depth, 0.9999991));
                return col;
            }
            ENDCG
        }
    }
}

阴影贴图

Shader "Shadow/ShadowMapNormal"
{
    Properties
    {
        _MainTex("Texture", 2D) = "white" {}
    }
    SubShader
    {
        Pass
        {
            CGPROGRAM

            #pragma vertex vert
            #pragma fragment frag

            #pragma multi_compile_fog

            #include "UnityCG.cginc"

            sampler2D _MainTex;
            float4 _MainTex_ST;


            struct v2f {
                float4 pos: SV_POSITION;
                float4 worldPos: TEXCOORD0;
                float4 ShadowCoord : TEXCOORD3;
                float2 depth : TEXCOORD4;
            };


            float4x4 _ProjectionMatrix;
            sampler2D _DepthTexture;
            float _ShadowBias;

            v2f vert(appdata_full v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);

                // 通过投影矩阵变换到light空间(摄像机为原点)
                o.ShadowCoord = mul(_ProjectionMatrix, mul(unity_ObjectToWorld, v.vertex));
                // 这一步不太懂
				o.ShadowCoord.z = -(mul(_WorldToViewMatrix, mul(unity_ObjectToWorld, v.vertex)).z * 1/200.0);
                return o;
            }

            fixed4 frag(v2f i) : SV_Target
            {
                fixed4 col = fixed4(1,1,1,1);

				float planeDepth = i.ShadowCoord.z;
				
                fixed4 dcol = tex2Dproj(_DepthTexture, i.ShadowCoord);
                float boxDepth = DecodeFloatRGBA(dcol);

                float  shadow = planeDepth + 0.0025 > boxDepth ? 0.5 : 1.0;

                return col * shadow;
            }
            ENDCG
        }
    }
}

用代码赋值 获取投影矩阵啥的

/// 

/// 创建depth相机
/// 
/// 

public class DepthTextureCamera : MonoBehaviour
{
    Camera _camera;

    RenderTexture _rt;

    // 光照的角度
    public Transform lightTrans;

    Matrix4x4 bias = new Matrix4x4();

    [Range(0, 0.1f)]
    public float ShadowBias = 0.005f;

    [Range(1, 2000)]
    public int UVLightSize = 500;

    [Range(1, 10)]
    public float OrthographicSize = 10;


    void Start()
    {

        _camera = new GameObject().AddComponent<Camera>();
        _camera.name = "DepthCamera";
        _camera.depth = 2;
        _camera.clearFlags = CameraClearFlags.SolidColor;
        _camera.backgroundColor = Color.white;
        _camera.farClipPlane = 100;

        _camera.cullingMask = LayerMask.GetMask("Player");
        _camera.aspect = 1;
        _camera.transform.position = this.transform.position;
        _camera.transform.rotation = this.transform.rotation;
        _camera.transform.parent = this.transform;

        _camera.orthographic = true;
        _camera.orthographicSize = OrthographicSize;


        // 0.5 * x + 0.5  [-1, 1] => [0, 1]
        bias.SetRow(0, new Vector4(0.5f,  0,        0,      0.5f));
        bias.SetRow(1, new Vector4(0,     0.5f,     0,      0.5f));
        bias.SetRow(2, new Vector4(0,     0,        0.5f,   0.5f));
        bias.SetRow(3, new Vector4(0,     0,        0,      1));


        _rt = new RenderTexture(1024, 1024, 0);
        _rt.filterMode = FilterMode.Point;
        _camera.targetTexture = _rt;
        _camera.SetReplacementShader(Shader.Find("Shadow/DeapthTextureShader"), "RenderType");
    }

    void Update() 
    {
        _camera.orthographicSize = OrthographicSize;
        this.transform.eulerAngles = lightTrans.eulerAngles;
        _camera.Render();

        Matrix4x4 project = _camera.projectionMatrix;
        Matrix4x4 worldToView = _camera.worldToCameraMatrix;
        Matrix4x4 mtx = project * worldToView;

        mtx = bias * mtx;

        Shader.SetGlobalMatrix("_ProjectionMatrix", mtx);
        Shader.SetGlobalMatrix("_WorldToViewMatrix", worldToView);
        Shader.SetGlobalTexture("_DepthTexture", _rt);
        Shader.SetGlobalFloat("_ShadowBias", ShadowBias);
        Shader.SetGlobalFloat("UVLightSize", UVLightSize);
        Shader.SetGlobalVector("_EyePos", new Vector4(
            _camera.transform.position.x,
            _camera.transform.position.y,
            _camera.transform.position.z, 0));
    }


}