unity shader内置变量（时间）
纹理动画——序列帧动画
可以将序列的纹理按顺序选中后ctrl+6可以自动生成序列帧动画。
也可以通过shader：提供一张包含了关键帧的图像，重点在于需要在每个时刻计算该时刻下应该播放的关键帧的位置，并对该关键帧进行纹理采样。
Shader "Unity Shaders Book/Chapter 11/Image Sequence Animation" {
Properties {
_Color ("Color Tint", Color) = (1, 1, 1, 1)
_MainTex ("Image Sequence", 2D) = "white" {}
_HorizontalAmount ("Horizontal Amount", Float) = 4//横向几个关键帧
_VerticalAmount ("Vertical Amount", Float) = 4//竖向几个关键帧
_Speed ("Speed", Range(1, 100)) = 30//控制序列帧动画的播放速度
}
SubShader {
//序列帧图像通常是透明纹理，所以进行相关标签设置。
Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
Pass {
Tags { "LightMode"="ForwardBase" }
ZWrite Off
Blend SrcAlpha OneMinusSrcAlpha
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
fixed4 _Color;
sampler2D _MainTex;
float4 _MainTex_ST;
float _HorizontalAmount;
float _VerticalAmount;
float _Speed;
struct a2v {
float4 vertex : POSITION;
float2 texcoord : TEXCOORD0;
};
struct v2f {
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
};
v2f vert (a2v v) {
v2f o;
o.pos = UnityObjectToClipPos(v.vertex);
o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
return o;
}
fixed4 frag (v2f i) : SV_Target {
float time = floor(_Time.y * _Speed);
//计算出关键帧所在的行列索引数
float row = floor(time / _HorizontalAmount);
float column = time - row * _HorizontalAmount;
// half2 uv = float2(i.uv.x /_HorizontalAmount, i.uv.y / _VerticalAmount);
// uv.x += column / _HorizontalAmount;
// uv.y -= row / _VerticalAmount;
half2 uv = i.uv + half2(column, -row);
uv.x /= _HorizontalAmount;
uv.y /= _VerticalAmount;
fixed4 c = tex2D(_MainTex, uv);
c.rgb *= _Color;
return c;
}
ENDCG
}
}
FallBack "Transparent/VertexLit"
}
纹理动画——滚动的背景
如果要模拟第一层比第二层更远的效果，第一层的滚动速度要小于第二层的滚动速度。
Shader "Unity Shaders Book/Chapter 11/Scrolling Background" {
Properties {
_MainTex ("Base Layer (RGB)", 2D) = "white" {}//第一层
_DetailTex ("2nd Layer (RGB)", 2D) = "white" {}//第二层
_ScrollX ("Base layer Scroll Speed", Float) = 1.0//第一层水平滚动速度
_Scroll2X ("2nd layer Scroll Speed", Float) = 1.0//第二层水平滚动速度
_Multiplier ("Layer Multiplier", Float) = 1//纹理的整体亮度
}
SubShader {
Tags { "RenderType"="Opaque" "Queue"="Geometry"}
Pass {
Tags { "LightMode"="ForwardBase" }
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
sampler2D _MainTex;
sampler2D _DetailTex;
float4 _MainTex_ST;
float4 _DetailTex_ST;
float _ScrollX;
float _Scroll2X;
float _Multiplier;
struct a2v {
float4 vertex : POSITION;
float4 texcoord : TEXCOORD0;
};
struct v2f {
float4 pos : SV_POSITION;
float4 uv : TEXCOORD0;
};
v2f vert (a2v v) {
v2f o;
o.pos = UnityObjectToClipPos(v.vertex);
o.uv.xy = TRANSFORM_TEX(v.texcoord, _MainTex) + frac(float2(_ScrollX, 0.0) * _Time.y);
o.uv.zw = TRANSFORM_TEX(v.texcoord, _DetailTex) + frac(float2(_Scroll2X, 0.0) * _Time.y);
return o;
}
fixed4 frag (v2f i) : SV_Target {
fixed4 firstLayer = tex2D(_MainTex, i.uv.xy);
fixed4 secondLayer = tex2D(_DetailTex, i.uv.zw);
fixed4 c = lerp(firstLayer, secondLayer, secondLayer.a);
c.rgb *= _Multiplier;
return c;
}
ENDCG
}
}
FallBack "VertexLit"
}
顶点动画——流动的河流
使用正弦函数来模拟水流的波动效果，批处理会合并所有相关的模型，模型各自的模型空间就会失去，所需要关闭批处理操作：
Shader "Unity Shaders Book/Chapter 11/Water" {
Properties {
_MainTex ("Main Tex", 2D) = "white" {}//河流纹理
_Color ("Color Tint", Color) = (1, 1, 1, 1)//整体颜色
_Magnitude ("Distortion Magnitude", Float) = 1//水流波动的幅度
_Frequency ("Distortion Frequency", Float) = 1//波动频率
_InvWaveLength ("Distortion Inverse Wave Length", Float) = 10//波长的倒数
_Speed ("Speed", Float) = 0.5//移动速度
}
SubShader {
// Need to disable batching because of the vertex animation
Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" "DisableBatching"="True"}
Pass {
Tags { "LightMode"="ForwardBase" }
ZWrite Off
Blend SrcAlpha OneMinusSrcAlpha
Cull Off
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
sampler2D _MainTex;
float4 _MainTex_ST;
fixed4 _Color;
float _Magnitude;
float _Frequency;
float _InvWaveLength;
float _Speed;
struct a2v {
float4 vertex : POSITION;
float4 texcoord : TEXCOORD0;
};
struct v2f {
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
};
v2f vert(a2v v) {
v2f o;
float4 offset;
offset.yzw = float3(0.0, 0.0, 0.0);
offset.x = sin(_Frequency * _Time.y + v.vertex.x * _InvWaveLength + v.vertex.y * _InvWaveLength + v.vertex.z * _InvWaveLength) * _Magnitude;
o.pos = UnityObjectToClipPos(v.vertex + offset);//顶点动画
o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
o.uv += float2(0.0, _Time.y * _Speed);//纹理动画
return o;
}
fixed4 frag(v2f i) : SV_Target {
fixed4 c = tex2D(_MainTex, i.uv);
c.rgb *= _Color.rgb;
return c;
}
ENDCG
}
}
FallBack "Transparent/VertexLit"
}
顶点动画——广告牌
广告牌技术会根据视角方向来旋转一个被纹理着色的多边形（通常是简单的四边形），使多边形看起来好像总是对着摄像机，比如渲染烟雾、云朵、闪光效果等。
广告牌技术的本质是构建旋转矩阵：表面法线+指向上的方向+指向右的方向，再加锚点来控制多边形在空间中的位置。
计算过程：通过初始计算可以得到目标的表面法线和指向上的方向，但这两者通常不垂直。但其中一者是固定的。模拟草丛时，指向上的方向固定。模拟粒子效果时，表面法线固定。
假设法线固定：法线和指向上的方向叉乘得到指向右的方向，归一化后，法线和指向右的方向叉乘得到正交的指向上的方向：
Shader "Unity Shaders Book/Chapter 11/Billboard" {
Properties {
_MainTex ("Main Tex", 2D) = "white" {}
_Color ("Color Tint", Color) = (1, 1, 1, 1)
_VerticalBillboarding ("Vertical Restraints", Range(0, 1)) = 1 //用于调整是固定法线还是固定指向上的方向
}
SubShader {
// Need to disable batching because of the vertex animation
Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" "DisableBatching"="True"}
Pass {
Tags { "LightMode"="ForwardBase" }
ZWrite Off
Blend SrcAlpha OneMinusSrcAlpha
Cull Off
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "Lighting.cginc"
sampler2D _MainTex;
float4 _MainTex_ST;
fixed4 _Color;
fixed _VerticalBillboarding;
struct a2v {
float4 vertex : POSITION;
float4 texcoord : TEXCOORD0;
};
struct v2f {
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
};
v2f vert (a2v v) {
v2f o;
//所有计算都在模型空间下计算
// Suppose the center in object space is fixed
float3 center = float3(0, 0, 0);//模型空间原点作为锚点
//将视角方向变换到模型空间下
float3 viewer = mul(unity_WorldToObject,float4(_WorldSpaceCameraPos, 1));
float3 normalDir = viewer - center;//计算目标法线方向
// If _VerticalBillboarding equals 1, we use the desired view dir as the normal dir
// Which means the normal dir is fixed
// Or if _VerticalBillboarding equals 0, the y of normal is 0
// Which means the up dir is fixed
normalDir.y =normalDir.y * _VerticalBillboarding;//0乘normal的y代表固定向上的方向
normalDir = normalize(normalDir);
// Get the approximate up dir
// If normal dir is already towards up, then the up dir is towards front
float3 upDir = abs(normalDir.y) > 0.999 ? float3(0, 0, 1) : float3(0, 1, 0);
float3 rightDir = normalize(cross(upDir, normalDir));
upDir = normalize(cross(normalDir, rightDir));
// Use the three vectors to rotate the quad
float3 centerOffs = v.vertex.xyz - center;
float3 localPos = center + rightDir * centerOffs.x + upDir * centerOffs.y + normalDir * centerOffs.z;
o.pos = UnityObjectToClipPos(float4(localPos, 1));
o.uv = TRANSFORM_TEX(v.texcoord,_MainTex);
return o;
}
fixed4 frag (v2f i) : SV_Target {
fixed4 c = tex2D (_MainTex, i.uv);
c.rgb *= _Color.rgb;
return c;
}
ENDCG
}
}
FallBack "Transparent/VertexLit"
}
使用quad来作为广告牌，不能使用plane的原因是，代码建立在竖直摆放的多边形的基础上，多边形的顶点结构需要满足在模型空间下是竖直排列的，只有这样，才能使用vertex来计算得到正确的相对于中心的位置偏移量。
顶点动画的注意事项
取消批处理会增加drawcall，因此要尽量避免使用模型空间下的一些绝对位置和方向来计算，在广告牌中，可以利用顶点颜色来存储每个顶点到锚点的距离值。同样在阴影的时候，需要自定义shadowcaster的pass来确保阴影效果的正确：
Shader "Unity Shaders Book/Chapter 11/Vertex Animation With Shadow" {
Properties {
_MainTex ("Main Tex", 2D) = "white" {}
_Color ("Color Tint", Color) = (1, 1, 1, 1)
_Magnitude ("Distortion Magnitude", Float) = 1
_Frequency ("Distortion Frequency", Float) = 1
_InvWaveLength ("Distortion Inverse Wave Length", Float) = 10
_Speed ("Speed", Float) = 0.5
}
SubShader {
// Need to disable batching because of the vertex animation
Tags {"DisableBatching"="True"}
Pass {
Tags { "LightMode"="ForwardBase" }
Cull Off
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
sampler2D _MainTex;
float4 _MainTex_ST;
fixed4 _Color;
float _Magnitude;
float _Frequency;
float _InvWaveLength;
float _Speed;
struct a2v {
float4 vertex : POSITION;
float4 texcoord : TEXCOORD0;
};
struct v2f {
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
};
v2f vert(a2v v) {
v2f o;
float4 offset;
offset.yzw = float3(0.0, 0.0, 0.0);
offset.x = sin(_Frequency * _Time.y + v.vertex.x * _InvWaveLength + v.vertex.y * _InvWaveLength + v.vertex.z * _InvWaveLength) * _Magnitude;
o.pos = UnityObjectToClipPos(v.vertex + offset);
o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
o.uv += float2(0.0, _Time.y * _Speed);
return o;
}
fixed4 frag(v2f i) : SV_Target {
fixed4 c = tex2D(_MainTex, i.uv);
c.rgb *= _Color.rgb;
return c;
}
ENDCG
}
// Pass to render object as a shadow caster
Pass {
Tags { "LightMode" = "ShadowCaster" }
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma multi_compile_shadowcaster
#include "UnityCG.cginc"
float _Magnitude;
float _Frequency;
float _InvWaveLength;
float _Speed;
struct v2f {
V2F_SHADOW_CASTER;
};
v2f vert(appdata_base v) {
v2f o;
float4 offset;
offset.yzw = float3(0.0, 0.0, 0.0);
offset.x = sin(_Frequency * _Time.y + v.vertex.x * _InvWaveLength + v.vertex.y * _InvWaveLength + v.vertex.z * _InvWaveLength) * _Magnitude;
v.vertex = v.vertex + offset;
TRANSFER_SHADOW_CASTER_NORMALOFFSET(o)
return o;
}
fixed4 frag(v2f i) : SV_Target {
SHADOW_CASTER_FRAGMENT(i)
}
ENDCG
}
}
FallBack "VertexLit"
}
