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[Shader 着色器]冰霜效果的思考和实现
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http://game.ceeger.com/forum/read.php?tid=23209&fid=2
由于最近要做一个冰系的角色，就想能不能做一些冰霜效果。那么就试试吧，先弄一张原图：
1.常规的冰霜，最简单的要数霜冻的颜色变化，只需要减少亮度，增加蓝色分量。
片段着色器：
texcol *= fixed4(0.9, 0.9, 0.9, 1f);
texcol.b += 0.2;
效果如下：
虽然简单，但效果也十分一般。
2.如果你玩过冰火围城，它里面的冰冻效果则是更加金属化，给人的感觉是一层灰色滤镜再增加一点蓝色，然后顶部会更亮。
首先，我们要计算法线夹角，方便处理顶部更亮这部分。
顶点着色器：
float3 normal = mul(SCALED_NORMAL, (float3x3)_World2Object);
fixed dotProduct = dot(normal, fixed3(0, 1, 0)) / 2;
if(dotProduct <= 0)
{
dotProduct = 0;
}
o.color = dotProduct.xxx;
然后灰化整个角色，并且增加顶部亮度。
片段着色器：
float grey = dot(texcol.rgb, float3(0.299, 0.587, 0.114)) + i.color.x;
texcol = fixed4(grey, grey, grey, texcol.a);
texcol.r -= 0.15;
texcol.b += 0.15;
效果如下：
不过由于这个模型本身比较暗，所以看上去有点像雕像。但这似乎不是我们想要的效果呢，于是我打算换一个思路，让材质先变成霜。
增加了一张贴图，看看霜的效果：
哈哈，有点像冰棍了呢。但霜应该要亮一些，我打算增加下亮度，同时增加外发光。
顶点着色器：
fixed3 viewDir = normalize(ObjSpaceViewDir(v.vertex));
fixed dotProduct = 1 - dot(v.normal, viewDir);
o.color = smoothstep(0, 1, dotProduct);
o.color *= _RimColor;
片段着色器：
texcol.rgb += i.color;
效果:
可是这样就完全是冰棍了呢，我想要混合一下原始的像素，于是增加一个变量，控制一下混合。
片段着色器：
texcol = texcol * _Frezz + alpha * (1 - _Frezz);
设置效果：
通过控制滚动条可以调整混合比例，这个大概是64开的比例，看着还行吧。
但这样就结束的话还是差强人意，因为冰霜的变化太过规则了，我们很多时候希望的是随机变化，显得更自然。
再增加一张噪点贴图，通过获得贴图的值调整混合比例。
float ClipTex = tex2D (_RandomTex, i.uv).r ;
float ClipAmount = (_Frezz - ClipTex) / 2 + 0.5;
if(ClipAmount < 0)
{
ClipAmount = 0;
}
if(ClipAmount > 1)
{
ClipAmount = 1;
}
效果如下：
这样马马虎虎吧，如果还要继续就需要法线贴图，遗憾的是这个模型没有法线贴图。
如果有法线贴图，我们可以再法线贴图层面上增加冰霜的颜色变化。
最后 的完整shader代码：
本部分设定了隐藏,您已回复过了,以下是隐藏的内容
// Upgrade NOTE: replaced 'PositionFog()' with multiply of UNITY_MATRIX_MVP by position
// Upgrade NOTE: replaced 'V2F_POS_FOG' with 'float4 pos : SV_POSITION'
Shader "Custom/CharactorShaderCullOff" {
Properties {
_MainTex ("Base (RGB)", 2D) = "white" {}
_AlphaTex ("Base (RGB)", 2D) = "white" {}
_RandomTex ("Base (RGB)", 2D) = "white" {}
_RimColor ("Rim Color", Color) = (1, 0, 0, 1)
_Color("_Color", Color) = (0.5,0.5,0.5,1)
_Rampage("_Rampage", Float) = 0
_Frezz("_Frezz", Range(0, 1)) = 0
}
SubShader {
//Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
Pass {
cull off
Blend SrcAlpha OneMinusSrcAlpha
CGPROGRAM
// Upgrade NOTE: excluded shader from DX11 and Xbox360; has structs without semantics (struct v2f members pos1)
#pragma exclude_renderers d3d11 xbox360
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
struct appdata {
float4 vertex : POSITION;
float3 normal : NORMAL;
float2 texcoord : TEXCOORD0;
};
struct v2f {
half4 pos : SV_POSITION;
half2 uv : TEXCOORD0;
fixed3 color : COLOR;
};
uniform fixed4 _RimColor;
uniform fixed _Rampage;
uniform fixed _Frezz;
v2f vert (appdata_base v) {
v2f o;
o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
if(_Rampage == 1)
{
fixed3 viewDir = normalize(ObjSpaceViewDir(v.vertex));
fixed dotProduct = 1 - dot(v.normal, viewDir);
o.color = smoothstep(0, 1, dotProduct);
o.color *= _RimColor;
}
float3 normal = mul(SCALED_NORMAL, (float3x3)_World2Object);
fixed dotProduct = dot(normal, fixed3(0, 1, 0)) / 2;
if(dotProduct <= 0)
{
dotProduct = 0;
}
o.color += dotProduct.xxx;
o.uv = v.texcoord.xy;
return o;
}
uniform sampler2D _MainTex;
uniform sampler2D _AlphaTex;
uniform sampler2D _RandomTex;
uniform fixed4 _Color;
fixed4 frag(v2f i) : COLOR {
fixed4 texcol = tex2D(_MainTex, i.uv);
fixed4 alpha = tex2D(_AlphaTex, i.uv);
float ClipTex = tex2D (_RandomTex, i.uv).r ;
float ClipAmount = (_Frezz - ClipTex) / 2 + 0.5;
if(ClipAmount < 0)
{
ClipAmount = 0;
}
if(ClipAmount > 1)
{
ClipAmount = 1;
}
if(_Rampage == 1)
{
texcol.rgb += i.color;
}
texcol = texcol * ClipAmount + alpha * (1 - ClipAmount);
texcol.a = alpha.a;
clip(texcol.a - 0.5);
texcol *= _Color;
return texcol;
}
ENDCG
}
}
}
// Upgrade NOTE: replaced 'V2F_POS_FOG' with 'float4 pos : SV_POSITION'
Shader "Custom/CharactorShaderCullOff" {
Properties {
_MainTex ("Base (RGB)", 2D) = "white" {}
_AlphaTex ("Base (RGB)", 2D) = "white" {}
_RandomTex ("Base (RGB)", 2D) = "white" {}
_RimColor ("Rim Color", Color) = (1, 0, 0, 1)
_Color("_Color", Color) = (0.5,0.5,0.5,1)
_Rampage("_Rampage", Float) = 0
_Frezz("_Frezz", Range(0, 1)) = 0
}
SubShader {
//Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
Pass {
cull off
Blend SrcAlpha OneMinusSrcAlpha
CGPROGRAM
// Upgrade NOTE: excluded shader from DX11 and Xbox360; has structs without semantics (struct v2f members pos1)
#pragma exclude_renderers d3d11 xbox360
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
struct appdata {
float4 vertex : POSITION;
float3 normal : NORMAL;
float2 texcoord : TEXCOORD0;
};
struct v2f {
half4 pos : SV_POSITION;
half2 uv : TEXCOORD0;
fixed3 color : COLOR;
};
uniform fixed4 _RimColor;
uniform fixed _Rampage;
uniform fixed _Frezz;
v2f vert (appdata_base v) {
v2f o;
o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
if(_Rampage == 1)
{
fixed3 viewDir = normalize(ObjSpaceViewDir(v.vertex));
fixed dotProduct = 1 - dot(v.normal, viewDir);
o.color = smoothstep(0, 1, dotProduct);
o.color *= _RimColor;
}
float3 normal = mul(SCALED_NORMAL, (float3x3)_World2Object);
fixed dotProduct = dot(normal, fixed3(0, 1, 0)) / 2;
if(dotProduct <= 0)
{
dotProduct = 0;
}
o.color += dotProduct.xxx;
o.uv = v.texcoord.xy;
return o;
}
uniform sampler2D _MainTex;
uniform sampler2D _AlphaTex;
uniform sampler2D _RandomTex;
uniform fixed4 _Color;
fixed4 frag(v2f i) : COLOR {
fixed4 texcol = tex2D(_MainTex, i.uv);
fixed4 alpha = tex2D(_AlphaTex, i.uv);
float ClipTex = tex2D (_RandomTex, i.uv).r ;
float ClipAmount = (_Frezz - ClipTex) / 2 + 0.5;
if(ClipAmount < 0)
{
ClipAmount = 0;
}
if(ClipAmount > 1)
{
ClipAmount = 1;
}
if(_Rampage == 1)
{
texcol.rgb += i.color;
}
texcol = texcol * ClipAmount + alpha * (1 - ClipAmount);
texcol.a = alpha.a;
clip(texcol.a - 0.5);
texcol *= _Color;
return texcol;
}
ENDCG
}
}
}
