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，CSDN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 Toggles = new List();
	// 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();
		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 newKeyWords = new List();

			// 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：