用Unity Shader实现漫反射

Untiy原来的效果

image.png

逐顶点

Shader "Unlit/Chapter6DiffuseVertextLevel"
{
    Properties
    {
        _Diffuse("Diffuse", Color) = (1, 1, 1, 1)
    }
        SubShader
    {

        Pass
        {
            Tags { "LightMode" = "ForwardBase" }

            CGPROGRAM
            #pragma vertex vert 
            #pragma fragment frag
            #include "Lighting.cginc"
            fixed4 _Diffuse;
            struct a2v {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
            };
            struct v2f {
                float4 pos : SV_POSITION;
                fixed3 color : COLOR;
            };

            v2f vert(a2v v) {
                v2f obj;
                // Transform
                obj.pos = UnityObjectToClipPos(v.vertex);

                // Get ambient term
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz;

                // Transform the normal fram obj space to world space
                fixed3 worldNormal = normalize(mul(v.normal, (float3x3)unity_WorldToObject));

                // Get the light diraction in world space
                fixed3 worldLight = normalize(_WorldSpaceLightPos0.xyz);

                // Compute diffuse term
                fixed3 diffuse = _LightColor0.rgb * _Diffuse.rgb * saturate(dot(worldNormal, worldLight));
                obj.color = ambient + diffuse;
                return obj;
            }

            fixed4 frag(v2f i) : SV_Target{
                return fixed4(i.color, 1.0);
            }
            ENDCG
        }
    }
    Fallback "Diffuse"

}

最终效果

image.png

image.png

可以看到逐顶点着色在边缘有锯齿感，逐像素着色可以解决这个问题

逐像素着色

Shader "Unlit/Chapter6DiffusePixelLevel"
{
    Properties
    {
        _Diffuse("Diffuse", Color) = (1, 1, 1, 1)
    }
        SubShader
    {

        Pass
        {
            Tags { "LightMode" = "ForwardBase" }

            CGPROGRAM
            #pragma vertex vert 
            #pragma fragment frag
            #include "Lighting.cginc"
            fixed4 _Diffuse;

            struct a2v {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
            };
            struct v2f {
                float4 pos : SV_POSITION;
                float3 worldNormal: TEXCOORD0;
            };

            v2f vert(a2v v) {
                v2f obj;
                // Transform
                obj.pos = UnityObjectToClipPos(v.vertex);

                obj.worldNormal = mul(v.normal, (float3x3)unity_WorldToObject);
               
                return obj;
            }

            fixed4 frag(v2f i) : SV_Target{
                // Get ambient term
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz;

                // Transform the normal fram obj space to world space
                fixed3 worldNormal = normalize(i.worldNormal);

                // Get the light diraction in world space
                fixed3 worldLight = normalize(_WorldSpaceLightPos0.xyz);

                // Compute diffuse term
                fixed3 diffuse = _LightColor0.rgb * _Diffuse.rgb * saturate(dot(worldNormal, worldLight));
                fixed3 color = ambient + diffuse;
                return fixed4(color, 1.0);
            }
            ENDCG
        }
    }
        Fallback "Diffuse"

}

image.png

可以看到边缘锯齿感好很多了，但是阴影是全黑的，不太行

半兰伯特模型

经验公式

fixed4 frag(v2f i): SV_Target{
                ...
                fixed halfLamber = dot(worldNormal, worldLight) * 0.5 + 0.5;
                fixed3 diffuse = _LightColor0.rgb * _Diffuse.rgb * halfLamber;
                fixed3 color = ambient + diffuse;
}

image.png