Unity3D眼镜Shader技术实现

笔者介绍：姜雪伟，IT公司技术合伙人，IT高级讲师，CSDN社区专家，特邀编辑，畅销书作者，已出版书籍：《手把手教你架构3D游戏引擎》电子工业出版社和《Unity3D实战核心技术详解》电子工业出版社等。

CSDN视频网址：http://edu.csdn.net/lecturer/144

最近在利用Shader实现眼镜的反射，透明以及高光，法线等效果，Unity虽然为我们提供了很多的Shader，但是在实际项目开发中，大部分不能直接使用，因为项目的需求要求实现的渲染效果时比较细致的，我们项目目前实现的眼镜渲染比较贴近于真实的眼镜，这就要求我们要明白其实现原理，然后将其调试出来，我们的眼镜分为三部分：镜框，镜面，眼鼻三部分。

每一部分都单独对其进行渲染处理，当然如果你讲它们合并在一起也是可以的，镜框的实现需要我们使用法线和原图两张材质就实现了高光，法线效果，非常炫，实现效果如下所示：

接下来实现镜面效果，在这里使用了Cubemap和Diffuse模拟真实环境中的镜面反射效果，实现如下所示：

最后一个是镜鼻的实现，它的实现比较简单只是用了透明处理，实现的效果如下所示：

而且实现了透明遮挡处理，以上就是关于眼镜的实现效果，下面把眼镜镜面的渲染代码给读者展示如下：

Shader "Custom/Glass_Mirror" {
    Properties {
        _cubemap ("cubemap", Cube) = "_Skybox" {}
        _cubemap_slider ("cubemap_slider", Range(0, 1)) = 1
        _color ("color", Color) = (0.5,0.5,0.5,1)
        _texture_diffuse ("texture_diffuse", 2D) = "white" {}
        _alpha_slider ("_alpha_slider", Range(0, 1)) = 1
    }
    SubShader {
		Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}

		Blend SrcAlpha OneMinusSrcAlpha 

        Pass {
//            Name "FORWARD"
//           Tags {
//                "LightMode"="ForwardBase"
//            }
            
            
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #define UNITY_PASS_FORWARDBASE
            #include "UnityCG.cginc"
            #include "AutoLight.cginc"

            #include "UnityPBSLighting.cginc"
            #include "UnityStandardBRDF.cginc"
            #pragma multi_compile_fwdbase_fullshadows
            //#pragma multi_compile_fog
            //#pragma exclude_renderers gles3 metal d3d11_9x xbox360 xboxone ps3 ps4 psp2 
            #pragma target 3.0
           // uniform float4 _LightColor0;
            uniform samplerCUBE _cubemap;
            uniform float _cubemap_slider;
            uniform float4 _color;
            uniform sampler2D _texture_diffuse; uniform float4 _texture_diffuse_ST;
            uniform float _alpha_slider;
            struct VertexInput {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
                float2 texcoord0 : TEXCOORD0;
            };
            struct VertexOutput {
                float4 pos : SV_POSITION;
                float2 uv0 : TEXCOORD0;
                float4 posWorld : TEXCOORD1;
                float3 normalDir : TEXCOORD2;
                LIGHTING_COORDS(3,4)
                UNITY_FOG_COORDS(5)
            };
            VertexOutput vert (VertexInput v) {
                VertexOutput o = (VertexOutput)0;
                o.uv0 = v.texcoord0;
                o.normalDir = UnityObjectToWorldNormal(v.normal);
                o.posWorld = mul(unity_ObjectToWorld, v.vertex);
                float3 lightColor = _LightColor0.rgb;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex );
                UNITY_TRANSFER_FOG(o,o.pos);
                TRANSFER_VERTEX_TO_FRAGMENT(o)
                return o;
            }
            float4 frag(VertexOutput i) : COLOR {
                i.normalDir = normalize(i.normalDir);
                float3 viewDirection = normalize(_WorldSpaceCameraPos.xyz - i.posWorld.xyz);
                float3 normalDirection = i.normalDir;
                float3 viewReflectDirection = reflect( -viewDirection, normalDirection );
                float3 lightDirection = normalize(_WorldSpaceLightPos0.xyz);
                float3 lightColor = _LightColor0.rgb;
                float3 halfDirection = normalize(viewDirection+lightDirection);
////// Lighting:
                float attenuation = LIGHT_ATTENUATION(i);
                float3 attenColor = attenuation * _LightColor0.rgb;
                ////
                float Pi = 3.141592654;
                float InvPi = 0.31830988618;
                /////
///////// Gloss:
                float gloss = 0.8;
                float specPow = exp2( gloss * 10.0+1.0);

                /////// GI Data:
                UnityLight light;
                #ifdef LIGHTMAP_OFF
                    light.color = lightColor;
                    light.dir = lightDirection;
                    light.ndotl = LambertTerm (normalDirection, light.dir);
                #else
                    light.color = half3(0.f, 0.f, 0.f);
                    light.ndotl = 0.0f;
                    light.dir = half3(0.f, 0.f, 0.f);
                #endif
                UnityGIInput d;
                d.light = light;
                d.worldPos = i.posWorld.xyz;
                d.worldViewDir = viewDirection;
                d.atten = attenuation;
                d.boxMax[0] = unity_SpecCube0_BoxMax;
                d.boxMin[0] = unity_SpecCube0_BoxMin;
                d.probePosition[0] = unity_SpecCube0_ProbePosition;
                d.probeHDR[0] = unity_SpecCube0_HDR;
                d.boxMax[1] = unity_SpecCube1_BoxMax;
                d.boxMin[1] = unity_SpecCube1_BoxMin;
                d.probePosition[1] = unity_SpecCube1_ProbePosition;
                d.probeHDR[1] = unity_SpecCube1_HDR;
                Unity_GlossyEnvironmentData ugls_en_data;
                ugls_en_data.roughness = 1.0 - gloss;
                ugls_en_data.reflUVW = viewReflectDirection;
                UnityGI gi = UnityGlobalIllumination(d, 1, normalDirection, ugls_en_data );
                lightDirection = gi.light.dir;
                lightColor = gi.light.color;
////// Specular:
                float NdotL = max(0, dot( normalDirection, lightDirection ));
                float LdotH = max(0.0,dot(lightDirection, halfDirection));
                float3 specularColor = 0.0;
                float specularMonochrome;
                float node_5610 = 0.2;
                float3 diffuseColor = float3(node_5610,node_5610,node_5610); // Need this for specular when using metallic
                diffuseColor = DiffuseAndSpecularFromMetallic( diffuseColor, specularColor, specularColor, specularMonochrome );
                specularMonochrome = 1.0-specularMonochrome;
                float NdotV = max(0.0,dot( normalDirection, viewDirection ));
                float NdotH = max(0.0,dot( normalDirection, halfDirection ));
                float VdotH = max(0.0,dot( viewDirection, halfDirection ));
                float visTerm = SmithJointGGXVisibilityTerm( NdotL, NdotV, 1.0-gloss );
                float normTerm = max(0.0, GGXTerm(NdotH, 1.0-gloss));
                float specularPBL = (NdotL*visTerm*normTerm) * (UNITY_PI / 4);
                if (IsGammaSpace())
                    specularPBL = sqrt(max(1e-4h, specularPBL));
                specularPBL = max(0, specularPBL * NdotL);
                float3 directSpecular = (floor(attenuation) * _LightColor0.rgb)*specularPBL*FresnelTerm(specularColor, LdotH);
                half grazingTerm = saturate( gloss + specularMonochrome );
                float3 indirectSpecular = (gi.indirect.specular);
                indirectSpecular *= FresnelLerp (specularColor, grazingTerm, NdotV);
                float3 specular = (directSpecular + indirectSpecular);

/////// Diffuse:
                //float NdotL = max(0.0,dot( normalDirection, lightDirection ));
                float3 directDiffuse = max( 0.0, NdotL) * attenColor;
                 float3 indirectDiffuse = float3(0,0,0);
                indirectDiffuse *= UNITY_LIGHTMODEL_AMBIENT.rgb; // Ambient Light
                float3 node_307 = (texCUBE(_cubemap,viewReflectDirection).rgb*_cubemap_slider);

                //indirectDiffuse += float3(node_307,node_307,node_307); // Diffuse Ambient Light
                indirectDiffuse += node_307;
                float4 _texture_diffuse_var = tex2D(_texture_diffuse,i.uv0);

                 diffuseColor = (_texture_diffuse_var.rgb);
                float3 diffuse = (directDiffuse + indirectDiffuse) * diffuseColor;
                //float3 diffuse = node_307 + diffuseColor;
/// Final Color:
                float3 finalColor = diffuse + specular;
                //float3 finalColor = diffuseColor;
                fixed4 finalRGBA = fixed4(finalColor,_alpha_slider);
                UNITY_APPLY_FOG(i.fogCoord, finalRGBA);
                return finalRGBA;
            }
            ENDCG
        }
       

    }
    FallBack "Diffuse"
}

其实就是利用了反射，法线，透明这些基本的技术综合在一起实现了镜面的Shader处理。。。。