Unity3D引擎之高级渲染技术

笔者介绍：姜雪伟，IT公司技术合伙人，IT高级讲师，****社区专家，特邀编辑，畅销书作者，国家专利发明人，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》电子工业出版社等书籍

在游戏开发中尤其对于角色的材质渲染一直是被游戏开发者所看重，也成为衡量游戏品质的一个指标，关于渲染就需要考虑到Shader编程，Shader主要是对模型的顶点和模型的材质图片做处理，下面告诉读者如何去编写Shader。

在公司，策划需求提出用Unity3D引擎实现角色材质高光、法线效果。策划需求提出后，美术首先用PS和MAX工具将模型制作出来，MAX中有自身带的Shader，它可以完整的实现高光、法线效果，这也是程序编写和调试Shader时的参照依据，程序是参照MAX中的效果去调试，程序实现的效果只能无限接近MAX工具制作的效果。Unity5.4以上版本也有自己的高光法线Shader，但是在使用时效果并不理想，不如自己去实现一下。在这里首先需要提供三张贴图：Diffuse(原图)，Specular(高光)，Normal(法线)。

接下来就需要对其进行Shader编程实现，为了让美术调试方便，在这里我们使用了控制面板。首先实现一个继承于Materal类的编辑器脚本，将其放到Editor文件夹下面，内容如下所示：

using System.Collections.Generic;using UnityEngine;using UnityEditor;using System.Linq;using System.Text.RegularExpressions;public abstract class CustomMaterialEditor : MaterialEditor{ public class FeatureEditor {  // The name the toggle will have in the inspector.  public string InspectorName;  // We will look for properties that contain this word, and hide them if we're not enabled.  public string InspectorPropertyHideTag;  // The keyword that the shader uses when this feature is enabled or disabled.  public string ShaderKeywordEnabled;  public string ShaderKeywordDisabled;  // The current state of this feature.  public bool Enabled;  public FeatureEditor(string InspectorName, string InspectorPropertyHideTag, string ShaderKeywordEnabled, string ShaderKeywordDisabled)  {   this.InspectorName = InspectorName;   this.InspectorPropertyHideTag = InspectorPropertyHideTag;   this.ShaderKeywordEnabled = ShaderKeywordEnabled;   this.ShaderKeywordDisabled = ShaderKeywordDisabled;   this.Enabled = false;  } } // A list of all the toggles that we have in this material editor. protected List<FeatureEditor> Toggles = new List<FeatureEditor>(); // This function will be implemented in derived classes, and used to populate the list of toggles. protected abstract void CreateToggleList();  public override void OnInspectorGUI () {  // if we are not visible... return  if (!isVisible)   return;  // Get the current keywords from the material  Material targetMat = target as Material;  string[] oldKeyWords = targetMat.shaderKeywords;  // Populate our list of toggles  //Toggles.Clear();  Toggles = new List<FeatureEditor>();  CreateToggleList();  // Update each toggle to enabled if it's enabled keyword is present. If it's enabled keyword is missing, we assume it's disabled.  for(int i = 0; i < Toggles.Count; i++)  {   Toggles[i].Enabled = oldKeyWords.Contains (Toggles[i].ShaderKeywordEnabled);  }  // Begin listening for changes in GUI, so we don't waste time re-applying settings that haven't changed.  EditorGUI.BeginChangeCheck();  serializedObject.Update ();  var theShader = serializedObject.FindProperty ("m_Shader");  if (isVisible && !theShader.hasMultipleDifferentValues && theShader.objectReferenceValue != null)  {   float controlSize = 64;   EditorGUIUtility.labelWidth = Screen.width - controlSize - 20;   EditorGUIUtility.fieldWidth = controlSize;   Shader shader = theShader.objectReferenceValue as Shader;   EditorGUI.BeginChangeCheck();   // Draw Non-toggleable values   for (int i = 0; i < ShaderUtil.GetPropertyCount(shader); i++)   {    ShaderPropertyImpl(shader, i, null);   }   // Draw toggles, then their values.   for (int s = 0; s < Toggles.Count; s++)   {    EditorGUILayout.Separator();    Toggles[s].Enabled = EditorGUILayout.BeginToggleGroup(Toggles[s].InspectorName, Toggles[s].Enabled);    if (Toggles[s].Enabled)    {     for (int i = 0; i < ShaderUtil.GetPropertyCount(shader); i++)     {      ShaderPropertyImpl(shader, i, Toggles[s]);     }    }    EditorGUILayout.EndToggleGroup();   }   if (EditorGUI.EndChangeCheck())    PropertiesChanged ();  }  // If changes have been made, then apply them.  if (EditorGUI.EndChangeCheck())  {   // New list of key words.   List<string> newKeyWords = new List<string>();   // If true, add the enabled keyword (ending with _ON), if false, add the disabled keyword(ending with _OFF).   for(int i = 0; i < Toggles.Count; i++)   {    newKeyWords.Add(Toggles[i].Enabled ? Toggles[i].ShaderKeywordEnabled : Toggles[i].ShaderKeywordDisabled);   }   // Send the new list of keywords to the material, this will define what version of the shader to use.   targetMat.shaderKeywords = newKeyWords.ToArray ();   EditorUtility.SetDirty (targetMat);  } } // This runs once for every property in our shader. private void ShaderPropertyImpl(Shader shader, int propertyIndex, FeatureEditor currentToggle) {  string propertyDescription = ShaderUtil.GetPropertyDescription(shader, propertyIndex);  // If current toggle is null, we only want to show properties that aren't already "owned" by a toggle,  // so if it is owned by another toggle, then return.  if (currentToggle == null)  {   for (int i = 0; i < Toggles.Count; i++)   {    if (Regex.IsMatch(propertyDescription, Toggles[i].InspectorPropertyHideTag , RegexOptions.IgnoreCase))    {     return;    }   }  }  // Only draw if we the current property is owned by the current toggle.  else if (!Regex.IsMatch(propertyDescription, currentToggle.InspectorPropertyHideTag , RegexOptions.IgnoreCase))  {   return;  }  // If we've gotten to this point, draw the shader property regulairly.  ShaderProperty(shader,propertyIndex); }}

上面是我们自己实现的可以作为父类使用，其实就是做了一个接口封装，下面代码是自己定义的为我们自己的Shader脚本操作写的几个开关。如下所示：

using System.Collections.Generic;using UnityEngine;using UnityEditor; public class EditorInspector : CustomMaterialEditor{    protected override void CreateToggleList()    {        Toggles.Add(new FeatureEditor("Normal Enabled","normal","NORMALMAP_ON","NORMALMAP_OFF"));        Toggles.Add(new FeatureEditor("Specular Enabled","specular","SPECULAR_ON","SPECULAR_OFF"));        Toggles.Add(new FeatureEditor("Fresnel Enabled","fresnel","FRESNEL_ON","FRESNEL_OFF"));        Toggles.Add(new FeatureEditor("Rim Light Enabled","rim","RIMLIGHT_ON","RIMLIGHT_OFF"));    }} 

相对来说比较简单，它只是做了几个Toggle作为Shader脚本中的控制。将上述两个文件拖放到Editor文件夹下面。

  下面才开始真正的Shader编写工作，在这里我们使用了SurfaceOutput作为我们的输出结构体，SurfaceOutput简单地描述了surface的属性（  properties of the surface ），如反射率颜色（albedo color）、法线（normal）、散射（emission）、镜面反射（specularity ）等。首先定义一个输入结构体如下所示：

struct Input        {            float2 uv_DiffuseMap;            #if SPECULAR_ON            float2 uv_SpecMap;            #endif            #if NORMALMAP_ON            float2 uv_NormalMap;            #endif            #if FRESNEL_ON || RIMLIGHT_ON            float3 viewDir;            #endif        }; 

结构体中包含 Diffuse贴图的uv坐标uv_DiffuseMap，高光的uv坐标uv_SpecMap，法线的uv坐标uv_NormalMap，另外还定义了一个方向值viewDir。接下来就是实现主函数surf了，对于高光法线的渲染就在这里面了，它调用了大量的CG库函数，如下所示：

 void surf (Input IN, inout SurfaceOutput o)        {              float3 TexData = tex2D(_DiffuseMap, IN.uv_DiffuseMap);            float3 _BlendColor =  _TintColor.rgb * _TintColorMultiply;                         o.Albedo.rgb = _Brightness * lerp(TexData, _TintColor.rgb, _TintColorMultiply) ;                         #if SPECULAR_ON            o.Specular = _Gloss;            o.Gloss = max(_SpecAdd + _SpecularMultiply, 1.0) * tex2D (_SpecMap, IN.uv_SpecMap);            //o.Emission = _Gloss * tex2D (_SpecMap, IN.uv_SpecMap);            #endif            #if NORMALMAP_ON            o.Normal = UnpackNormal(tex2D(_NormalMap, IN.uv_NormalMap));            #endif                     #if FRESNEL_ON && SPECULAR_ON || RIMLIGHT_ON            float facing = saturate(1.0 - max(dot(normalize(IN.viewDir), normalize(o.Normal)), 0.0));                 #if FRESNEL_ON && SPECULAR_ON                float fresnel = max(_FresnelBias + (1.0-_FresnelBias) * pow(facing, _FresnelPower), 0);                fresnel = fresnel * o.Specular * _FresnelMultiply;                o.Gloss *= 1+fresnel;                #endif                        #if RIMLIGHT_ON                float rim = max(_RimBias + (1.0-_RimBias) * pow(facing, _RimPower), 0);                rim = rim * o.Specular * _RimMultiply;                o.Albedo *= 1+rim;                #endif            #endif                 } 

下面将Shader的完整代码展示如下：

Shader "Custom_Shaders/DNSRender"{    Properties    {        _TintColor ("Color Tint",color) = (1.0,1.0,1.0,1.0)        //Diffuse Sliders        _TintColorMultiply("Color Tint Multiply", Range(0.0, 1.0)) = 0.0        _Brightness ("Diffuse Brightness", Range(0.0, 2.0)) = 1.0        _DiffuseMap ("Diffuse (RGB)", 2D) = "white" {}        _NormalMap ("Normal Map(RGB)", 2D) = "bump" {}        _SpecColor ("Specular Color", Color) = (0.5, 0.5, 0.5, 1)        _SpecularMultiply ("Specular Brightness",float) = 1.0        _SpecAdd ("Specular Boost", float) = 0        _SpecMap ("Specular Map (RGB)", 2D) = "grey" {}        _Gloss ("Specular Glossiness", float) = 0.5        _FresnelPower ("Fresnel Power",float) = 1.0        _FresnelMultiply ("Fresnel Multiply", float) = 0.2        _FresnelBias ("Fresnel Bias", float) = -0.1        _RimPower ("RimLight Power",float) = 1.0        _RimMultiply ("RimLight Multiply", float) = 0.2        _RimBias ("RimLight Bias", float) = 0        _EmissionColor("Emission Color", color) = (1.0,1.0,1.0,1.0)    }    SubShader    {        Tags { "RenderType"="Opaque" }        LOD 300        CGPROGRAM        #pragma surface surf BlinnPhong        #pragma target 3.0        #pragma shader_feature NORMALMAP_ON NORMALMAP_OFF        #pragma shader_feature SPECULAR_ON SPECULAR_OFF        #pragma shader_feature FRESNEL_ON FRESNEL_OFF        #pragma shader_feature RIMLIGHT_ON RIMLIGHT_OFF        float3 _TintColor;        float _TintColorMultiply;        float _Brightness;        sampler2D _DiffuseMap;        sampler2D _NormalMap;            sampler2D _SpecMap;        float _SpecularMultiply;        float _SpecAdd;        float _Gloss;        float _FresnelPower;        float _FresnelMultiply;        float _FresnelBias;        float _RimPower;        float _RimMultiply;        float _RimBias;        float3 _EmissionColor;        struct Input        {            float2 uv_DiffuseMap;            #if SPECULAR_ON            float2 uv_SpecMap;            #endif            #if NORMALMAP_ON            float2 uv_NormalMap;            #endif            #if FRESNEL_ON || RIMLIGHT_ON            float3 viewDir;            #endif        };         void surf (Input IN, inout SurfaceOutput o)        {              float3 TexData = tex2D(_DiffuseMap, IN.uv_DiffuseMap);            float3 _BlendColor =  _TintColor.rgb * _TintColorMultiply;                o.Albedo.rgb = _Brightness * lerp(TexData, _TintColor.rgb, _TintColorMultiply) ;                #if SPECULAR_ON            o.Specular = _Gloss;            o.Gloss = max(_SpecAdd + _SpecularMultiply, 1.0) * tex2D (_SpecMap, IN.uv_SpecMap);            //o.Emission = _Gloss * tex2D (_SpecMap, IN.uv_SpecMap);            #endif            #if NORMALMAP_ON            o.Normal = UnpackNormal(tex2D(_NormalMap, IN.uv_NormalMap));            #endif                     #if FRESNEL_ON && SPECULAR_ON || RIMLIGHT_ON            float facing = saturate(1.0 - max(dot(normalize(IN.viewDir), normalize(o.Normal)), 0.0));                 #if FRESNEL_ON && SPECULAR_ON                float fresnel = max(_FresnelBias + (1.0-_FresnelBias) * pow(facing, _FresnelPower), 0);                fresnel = fresnel * o.Specular * _FresnelMultiply;                o.Gloss *= 1+fresnel;                #endif                        #if RIMLIGHT_ON                float rim = max(_RimBias + (1.0-_RimBias) * pow(facing, _RimPower), 0);                rim = rim * o.Specular * _RimMultiply;                o.Albedo *= 1+rim;                #endif            #endif                 }        ENDCG    }    CustomEditor "EditorInspector"} 

将Shader挂接到材质球上效果如下：

最终展示效果如下所示：