Unity Shader实现3D饼图

怀这一些堕落和伤感写下这篇文章，今天写想用Shader写一个3D饼图效果，居然没有想到别的更高效的写法，功能实现了更效率不高。希望看到此文章有更好实现方式的请私信我，谢谢。

代码本身看起来很长，其实只是把自身坐标顶点传入片元着色器，再判断所以点与中心的连线，与中心点的夹角的度数，判断使用哪个颜色。使用了大量的if else…求指正。

只需要哒到如下效果即可。

下面是原代码：

Shader "Custom/PieGraph" {
	Properties{
		_element1("element%1",Range(0.00,100.00))=0
		_element2("element%2",Range(0.00,100.00))=0
		_element3("element%3",Range(0.00,100.00))=0
		_element4("element%4",Range(0.00,100.00))=0
		_element5("element%5",Range(0.00,100.00))=0
		_element6("element%6",Range(0.00,100.00))=0
		_element7("element%7",Range(0.00,100.00))=0
		_element8("element%8",Range(0.00,100.00))=0
		_element9("element%9",Range(0.00,100.00))=0
		_Angle1Color("Color1",Color)=(1,1,1,1)
		_Angle2Color("Color2",Color)=(1,1,1,1)
		_Angle3Color("Color3",Color)=(1,1,1,1)
		_Angle4Color("Color4",Color)=(1,1,1,1)
		_Angle5Color("Color5",Color)=(1,1,1,1)
		_Angle6Color("Color6",Color)=(1,1,1,1)
		_Angle7Color("Color7",Color)=(1,1,1,1)
		_Angle8Color("Color8",Color)=(1,1,1,1)
		_Angle9Color("Color9",Color)=(1,1,1,1)

		
		_Diffuse("Diffuse",Color)=(0.1,0.1,0.1,1)
		_Specular("Specular",Color)=(1,1,1,1)
		_Gloss("Gloss",Range(8,256))=20
	}
	SubShader{
		Tags{"IgnoreProjector"="True"}

		Pass{
			Tags{"LightMode"="ForwardBase"}

			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#include "Lighting.cginc"

			fixed4 _Color;
			float _element1;
			float _element2;
			float _element3;
			float _element4;
			float _element5;
			float _element6;
			float _element7;
			float _element8;
			float _element9;
			fixed4 _Angle1Color;
			fixed4 _Angle2Color;
			fixed4 _Angle3Color;
			fixed4 _Angle4Color;
			fixed4 _Angle5Color;
			fixed4 _Angle6Color;
			fixed4 _Angle7Color;
			fixed4 _Angle8Color;
			fixed4 _Angle9Color;

			fixed4 _Diffuse;
			fixed4 _Specular;
			float _Gloss;
			
			struct a2v{
				float4 vertex:POSITION;
				float2 uv:TEXCOORD0;
				float3 normal:NORMAL;
			};
			
			struct v2f{
				float4 pos:SV_POSITION;
				float2 uv:TEXCOORD0;
				float4 objPos:TEXCOORD1;
				float3 worldPos:TEXCOORD2;
				float3 normal:TEXCOORD3;
			};

			v2f vert(a2v v){
				v2f o;
				o.pos = UnityObjectToClipPos(v.vertex);
				o.objPos = v.vertex;
				o.uv = v.uv;
				o.worldPos =mul(unity_ObjectToWorld,v.vertex);
				o.normal = normalize(mul(v.normal,(float3x3)unity_WorldToObject));

				return o;
			}
			   
			float4 frag(v2f i):SV_TARGET{

				float2 thisline = i.objPos.zx;
				float angle = atan2(thisline.y,thisline.x)*15.92;
				_element1 = _element1-50;

				_element2 +=_element1 ;
				_element3 +=_element2 ;
				_element4 +=_element3 ;
				_element5 +=_element4 ;
				_element6 +=_element5 ;
				_element7 +=_element6 ;
				_element8 +=_element7 ;
				_element9 +=_element8 ;
				
				fixed3 additionaryColor;
				if(angle<_element1){
					additionaryColor = _Angle1Color;
				}else if(angle<_element2){
					additionaryColor = _Angle2Color;
				}else if(angle<_element3){
					additionaryColor = _Angle3Color;
				}else if(angle<_element4){
					additionaryColor = _Angle4Color;
				}else if(angle<_element5){
					additionaryColor = _Angle5Color;
				}else if(angle<_element6){
					additionaryColor = _Angle6Color;
				}else if(angle<_element7){
					additionaryColor = _Angle7Color;
				}else if(angle<_element8){
					additionaryColor = _Angle8Color;
				}else if(angle<_element9){
					additionaryColor = _Angle9Color;
				}

				fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz;
				fixed3 worldLightDir = normalize(_WorldSpaceLightPos0.xyz);
				fixed3 diffuse = _LightColor0.rgb*_Diffuse.rgb*saturate(dot(i.normal,worldLightDir));
				fixed3 reflectDir = normalize(reflect(-worldLightDir,i.normal));
				fixed3 viewDir = normalize(_WorldSpaceCameraPos.xyz-i.worldPos.xyz);
				fixed3 specular = _LightColor0.rgb * _Specular.rgb *pow(saturate(dot(reflectDir,viewDir)),_Gloss);
				float3 color = (ambient+diffuse+specular)*additionaryColor;

				return fixed4(color,1);
			}
			ENDCG
		}
	}
}