Unity Shader入门教程（七）：基础纹理之单张纹理

发表于2018-06-06

一、基础纹理应用

纹理的最初目的就是使用一张图片来控制模型的外观。使用纹理映射技术，我们可以吧一张图“黏”在模型表面，逐纹素(texel)(名字是为了和逐像素进行区分)地控制模型的颜色。

结合之前的光照模型的单张纹理应用：

// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'
// Upgrade NOTE: replaced '_World2Object' with 'unity_WorldToObject'
Shader "Custom/Edu/SingleTexture" ｛
    Properties 
    ｛
        _MainTex("MainTex",2D)= "white"｛｝
        _Diffuse("Diffuse",Color) = (1,1,1,1)
        _Specular("Specular",Color) = (1,1,1,1)
        _Gloss("Gloss",Range(8,256)) = 40
        _Color("ColorTint",Color) = (1,1,1,1)
    ｝
    SubShader 
    ｛
        Pass
        ｛
            Tags｛"LightMode" = "ForwardBase"｝
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
            #include "Lighting.cginc"
            sampler2D _MainTex;
            float4 _MainTex_ST;
            fixed4 _Diffuse;
            fixed4 _Specular;
            fixed4 _Color;
            float _Gloss;
            struct a2v
            ｛
                float4 vertex:POSITION;
                float3 normal:NORMAL;
                float4 texcoord:TEXCOORD0;
            ｝;
            struct v2f
            ｛
                float4 pos:SV_POSITION;
                float3 worldNormal:TEXCOORD0;
                float3 worldPos:TEXCOORD1;
                float2 uv:TEXCOORD2;
            ｝;
            v2f vert(a2v v)
            ｛
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP,v.vertex);
                o.worldPos = mul(unity_ObjectToWorld,v.vertex);
                o.worldNormal = mul(v.normal,(float3x3)unity_WorldToObject);
                o.uv = TRANSFORM_TEX(v.texcoord,_MainTex);
                return o;
            ｝
            fixed4 frag(v2f i):SV_Target
            ｛
                fixed3 worldNormal = normalize(i.worldNormal);
                fixed3 worldLightDir = normalize(UnityWorldSpaceLightDir(i.worldPos));
                fixed3 albedo = tex2D(_MainTex,i.uv).rgb * _Color.rgb;
                fixed3 diffuse = _LightColor0.rgb * albedo * _Diffuse.rgb * saturate(dot(worldNormal,worldLightDir));
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.rgb * albedo;
                fixed3 viewDir = normalize(UnityWorldSpaceViewDir(i.worldPos));
                fixed3 halfDir = normalize(viewDir + worldLightDir);
                fixed3 specular = _LightColor0.rgb * _Specular.rgb * pow(saturate(dot(worldNormal,halfDir)),_Gloss);
                return fixed4( diffuse + ambient + specular , 1.0);
            ｝
            ENDCG
        ｝
    ｝
    FallBack "Diffuse"
｝

TRASFORM_TEX实在UnityCG.cginc中定义的：

/Transform 2D UV by scale/bias property
#define TRANSFORM_TEX(tex,name)(tex.xy * name##_ST.xy + name##_ST.zw)

它接受两个参数

第一个参数是顶点的纹理坐标

第二个参数是纹理的名称

看一下效果：

二、纹理采样区间设置

下面为了阐释纹理的属性，编写一个更为纯粹的纹理属性应用shader

Shader "Custom/Edu/SimpleTextureProperties" ｛
    Properties ｛
        _Color ("Color", Color) = (1,1,1,1)
        _MainTex ("Albedo (RGB)", 2D) = "white" ｛｝
    ｝
    SubShader 
    ｛
        Pass
        ｛
            Tags｛"LightMode" = "ForwardBase"｝
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
            #include "Lighting.cginc"
            sampler2D _MainTex;
            float4 _MainTex_ST;
            fixed4 _Color;
            struct a2v
            ｛
                float4 vertex:POSITION;
                float2 texcoord:TEXCOORD0;
            ｝;
            struct v2f
            ｛
                float4 pos:SV_POSITION;
                float2 uv:TEXCOORD0;
            ｝;
            v2f vert(a2v v)
            ｛
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP,v.vertex);
                o.uv = TRANSFORM_TEX(v.texcoord,_MainTex);
                return o;
            ｝
            fixed4 frag(v2f i):SV_Target
            ｛
                fixed3 color = tex2D(_MainTex,i.uv);
                return fixed4(color,1.0);
            ｝
            ENDCG
        ｝
    ｝
    FallBack "Diffuse"
｝

利用这个shader在场景中创建一个Quad。