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// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
// Upgrade NOTE: replaced '_World2Object' with 'unity_WorldToObject'
Shader "Unity Shaders Book/Chapter 11/Billboard"
{
Properties
{
_MainTex("Main Tex", 2D) = "white" {}
_Color("Color Tint", Color) = (1,1,1,1)
//调整时是固定法线还是固定指向上的方向,即约束垂直方向的程度
_VerticalBillboarding("Vertical Restraints", Range(0,1)) = 1
}
SubShader
{
//由于序列帧图像通常是透明背景所以需要设置pass的相关状态以渲染透明效果
//半透明“标配”,DisableBatching指明是否对该SubShader使用批处理批处理会合并所有相关模型模型各自的模型空间就会丢失
//广告牌技术需要使用物体的模型空间下的位置来作为锚点进行计算
Tags{ "Queue" = "Transparent" "IgnoreProject" = "True" "RenderType" = "Transparent" "DisableBatching" = "True" }
Pass
{
Tags{ "LightMode" = "ForwardBase" }
//为了让广告牌的每个面都能显示
//关闭深度写入
ZWrite off
//开启并设置混合模式
Blend SrcAlpha OneMinusSrcAlpha
//关闭剔除功能
Cull Off
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
sampler2D _MainTex;
float4 _MainTex_ST;
fixed4 _Color;
float _VerticalBillboarding;
struct a2v
{
float4 vertex : POSITION;
float4 texcoord : TEXCOORD0;
};
struct v2f
{
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
};
v2f vert(a2v v)
{
v2f o;
//选择模型空间的原点作为广告牌的锚点
float3 center = float3(0, 0, 0);
//获取模型空间下的视角位置
float3 viewer = mul(unity_WorldToObject, float4(_WorldSpaceCameraPos, 1));
//开始计算3个正交矢量
//根据观察方向和锚点计算目标法线方向
float3 normalDir = viewer - center;
//根据_VerticalBillboarding属性控制垂直方向上的约束
//当_VerticalBillboarding为1时法线方向固定为视角方向
//当_VerticalBillboarding为0时向上方向固定为(0,1,0)
//获得的法线方向需要进行归一化操作得到单位矢量
normalDir.y = normalDir.y * _VerticalBillboarding;
normalDir = normalize(normalDir);
//获得粗略的向上方向,为了方式法线方向和向上方向平行(如果平行,叉积会得到错误的结果)对法线方向的y分量进行判断
float3 upDir = abs(normalDir.y) > 0.999 ? float3(0, 0, 1) : float3(0, 1, 0);
//根据法线方向和粗略的向上方向得到向右方向,并归一化
float3 rightDir = normalize(cross(upDir, normalDir));
//根据法线方向和向右方向获得准确的向上方向
upDir = normalize(cross(normalDir, rightDir));
//根据原始的位置相对于锚点的偏移量以及3个正交基矢量以计算得到新的顶点位置
float3 centerOffs = v.vertex.xyz - center;
float3 localPos = center + rightDir * centerOffs.x + upDir * centerOffs.y + normalDir * centerOffs.z;
//把模型空间的顶点位置变换到裁剪空间
o.pos = UnityObjectToClipPos(float4(localPos, 1));
o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
return o;
}
fixed4 frag(v2f i) : SV_Target
{
//对纹理进行采样
fixed4 c = tex2D(_MainTex,i.uv);
//混合颜色
c.rgb *= _Color.rgb;
return c;
}
ENDCG
}
}
Fallback"Transparent/VertexLit"
}