Implementing Fixed Function TexGen in Shaders

在Unity 5之前，纹理属性可能在卷括号中有选项，例如TexGen CubeReflect. 这些控制固定功能纹理坐标生成。这个功能是在Unity 5删除；如果你需要TexGen你应该写一个顶点着色器代替。

本页说明如何在Unity4执行每一个固定功能的纹理生成模式。

Cubemap reflection (TexGen CubeReflect)

TexGen CubeReflect通常用于简单的立方体贴图的反射。它反映了视图沿法线方向的视图空间，并使用该作为UV坐标。

Shader "TexGen/CubeReflect" {
Properties {
    _Cube ("Cubemap", Cube) = "" { /* used to be TexGen CubeReflect */ }
}
SubShader { 
    Pass { 
        CGPROGRAM
        #pragma vertex vert
        #pragma fragment frag
        #include "UnityCG.cginc"

        struct v2f {
            float4 pos : SV_POSITION;
            float3 uv : TEXCOORD0;
        };

        v2f vert (float4 v : POSITION, float3 n : NORMAL)
        {
            v2f o;
            o.pos = UnityObjectToClipPos(v);

            // TexGen CubeReflect:
            // reflect view direction along the normal,
            // in view space
            float3 viewDir = normalize(ObjSpaceViewDir(v));
            o.uv = reflect(-viewDir, n);
            o.uv = mul(UNITY_MATRIX_MV, float4(o.uv,0));
            return o;
        }

        samplerCUBE _Cube;
        half4 frag (v2f i) : SV_Target
        {
            return texCUBE(_Cube, i.uv);
        }
        ENDCG 
    } 
}
}

Cubemap normal (TexGen CubeNormal)

TexGen CubeNormal is typically used with cubemaps too. It uses view space normal as the UV coordinate.

Shader "TexGen/CubeNormal" {
Properties {
    _Cube ("Cubemap", Cube) = "" { /* used to be TexGen CubeNormal */ }
}
SubShader { 
    Pass { 
        CGPROGRAM
        #pragma vertex vert
        #pragma fragment frag
        #include "UnityCG.cginc"

        struct v2f {
            float4 pos : SV_POSITION;
            float3 uv : TEXCOORD0;
        };

        v2f vert (float4 v : POSITION, float3 n : NORMAL)
        {
            v2f o;
            o.pos = UnityObjectToClipPos(v);

            // TexGen CubeNormal:
            // use view space normal of the object
            o.uv = mul((float3x3)UNITY_MATRIX_IT_MV, n);
            return o;
        }

        samplerCUBE _Cube;
        half4 frag (v2f i) : SV_Target
        {
            return texCUBE(_Cube, i.uv);
        }
        ENDCG 
    } 
}
}

Object space coordinates (TexGen ObjectLinear)

TexGen ObjectLinear used object space vertex position as UV coordinate.

Shader "TexGen/ObjectLinear" {
Properties {
    _MainTex ("Texture", 2D) = "" { /* used to be TexGen ObjectLinear */ }
}
SubShader { 
    Pass { 
        CGPROGRAM
        #pragma vertex vert
        #pragma fragment frag
        #include "UnityCG.cginc"

        struct v2f {
            float4 pos : SV_POSITION;
            float3 uv : TEXCOORD0;
        };

        v2f vert (float4 v : POSITION)
        {
            v2f o;
            o.pos = UnityObjectToClipPos(v);

            // TexGen ObjectLinear:
            // use object space vertex position
            o.uv = v.xyz;
            return o;
        }

        sampler2D _MainTex;
        half4 frag (v2f i) : SV_Target
        {
            return tex2D(_MainTex, i.uv.xy);
        }
        ENDCG 
    } 
}
}

View space coordinates (TexGen EyeLinear)

TexGen EyeLinear used view space vertex position as UV coordinate.

Shader "TexGen/EyeLinear" {
Properties {
    _MainTex ("Texture", 2D) = "" { /* used to be TexGen EyeLinear */ }
}
SubShader { 
    Pass { 
        CGPROGRAM
        #pragma vertex vert
        #pragma fragment frag
        #include "UnityCG.cginc"

        struct v2f {
            float4 pos : SV_POSITION;
            float3 uv : TEXCOORD0;
        };

        v2f vert (float4 v : POSITION)
        {
            v2f o;
            o.pos = UnityObjectToClipPos(v);

            // TexGen EyeLinear:
            // use view space vertex position
            o.uv = UnityObjectToViewPos(v);
            return o;
        }

        sampler2D _MainTex;
        half4 frag (v2f i) : SV_Target
        {
            return tex2D(_MainTex, i.uv.xy);
        }
        ENDCG 
    } 
}
}

Spherical environment mapping (TexGen SphereMap)

TexGen SphereMap computes UV coordinates for spherical environment mapping. See OpenGL TexGen reference for the formula.

Shader "TexGen/SphereMap" {
Properties {
    _MainTex ("Texture", 2D) = "" { /* used to be TexGen SphereMap */ }
}
SubShader { 
    Pass { 
        CGPROGRAM
        #pragma vertex vert
        #pragma fragment frag
        #include "UnityCG.cginc"

        struct v2f {
            float4 pos : SV_POSITION;
            float2 uv : TEXCOORD0;
        };

        v2f vert (float4 v : POSITION, float3 n : NORMAL)
        {
            v2f o;
            o.pos = UnityObjectToClipPos(v);

            // TexGen SphereMap
            float3 viewDir = normalize(ObjSpaceViewDir(v));
            float3 r = reflect(-viewDir, n);
            r = mul((float3x3)UNITY_MATRIX_MV, r);
            r.z += 1;
            float m = 2 * length(r);
            o.uv = r.xy / m + 0.5;

            return o;
        }

        sampler2D _MainTex;
        half4 frag (v2f i) : SV_Target
        {
            return tex2D(_MainTex, i.uv);
        }
        ENDCG 
    } 
}
}