先看终于效果：

我们的原图是一个3D模型的截图：

这一效果是通过Shader实现的：

（Shader代码来自国外博客：http://www.thomas-joncorpuz.com/blog/2014/11/30/custom-unity-2d-sprite-shader）

Shader "Custom/SpriteNormal" {Properties{[PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}_NormalsTex ("Sprite Normals", 2D) = "bump" {}_Ramp ("Shading Ramp", 2D) = "white" {}_Color ("Tint", Color) = (1,1,1,1)[MaterialToggle] PixelSnap ("Pixel snap", Float) = 0_Cutoff ("Alpha Cutoff", Range (0,1)) = 0.5}SubShader{Tags{ "Queue"="Transparent" "IgnoreProjector"="False" "RenderType"="Transparent" "PreviewType"="Plane""CanUseSpriteAtlas"="True"}Cull OffLighting OnZWrite OffFog { Mode Off }Blend SrcAlpha OneMinusSrcAlphaCGPROGRAM#pragma surface surf CustomLambert alpha vertex:vert addshadow alphatest:_Cutoff #pragma multi_compile DUMMY PIXELSNAP_ONsampler2D _MainTex;sampler2D _NormalsTex;sampler2D _Ramp;fixed4 _Color;struct Input{float2 uv_MainTex;fixed4 color;};half4 LightingCustomLambert (SurfaceOutput s, half3 lightDir, half3 viewDir, half atten) {half NdotL = dot (s.Normal, lightDir);half4 c;c.rgb = (s.Albedo * _LightColor0.rgb * (tex2D (_Ramp, half2 (NdotL * 0.5 + 0.5, 0)))) * (atten * 2);c.a = s.Alpha;return c;}void vert (inout appdata_full v, out Input o){#if defined(PIXELSNAP_ON) && !defined(SHADER_API_FLASH)v.vertex = UnityPixelSnap (v.vertex);#endifv.normal = float3(0,0,-1);v.tangent = float4(-1, 0, 0, 1);UNITY_INITIALIZE_OUTPUT(Input, o);o.color = _Color * v.color;}void surf (Input IN, inout SurfaceOutput o){fixed4 c = tex2D(_MainTex, IN.uv_MainTex) * IN.color;o.Albedo = c.rgb;o.Normal = UnpackNormal (tex2D (_NormalsTex, IN.uv_MainTex));o.Alpha = c.a;}ENDCG} FallBack "Diffuse"
}

Shader须要的法线贴图能够通过一个软件：PixPlant生成出来，仅仅需提供原素材图。这个软件就能生成一个法线贴图了。

此外还须要一张阴影梯度图：