【风宇冲】Shader:二十六Tessellation_风宇冲

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【风宇冲】Shader:二十六Tessellation

(2016-01-27 11:39:33)

分类： Unity3d之Shader篇

原创文章如需转载请注明：转载自风宇冲博客

Shader第二十六讲 Tessellation

Unity 5.1之前的版本，OpenGL ES2.0 、3.0 、desktop OpenGL的渲染都是分别的版本。而5.1，unity使用统一的OpenGL Core，所以一些渲染的新功能DX和OpenGL都可以使用:
Tessellation Shader:细分曲面。Geometry Shader:几何Shader。
Compute Shader: 计算Shader。

(1)使用要求：

【Tessellation Shader/Geometry Shader】

PC/Console: Shader Model 4.6 + DX11/OpenGL Core

安卓平台: OpenGL ES 3.1 + AEP(Android Extension Pack)

【Compute Shader】

PC/Console: DX11/OpenGL desktop 4.3+

安卓平台: OpenGL ES 3.1+

(2)开启：

最好是在Player Settings里关掉Auto Graphics API.

做PC/Console的话

直接选择例如DX11即可

移动端的话

Computer Shader 建议用Vulkan

Tessellation/Geometry 建议用 OpenGLES3 + Require ES3.1 + AEP

http://s10/mw690/001iGO8Gzy7aosFjdpvd9&690

简而言之，Instancing/Compute Shader/Tessellation Shader/Geometry Shader

在电脑/家用机/移动端都可以运行(只要显卡支持)

下面用一张图说明这些Shader的关系。

http://s3/mw690/001iGO8Ggy6YVumJNke22&690

本讲就来介绍Tessellation细分曲面。
当我们显示普通的模型时，效果一般，于是有了法线贴图。但是法线贴图有局限性，例如入视角。而DX11的
Tessellation是真正的生成更细致的mesh。一句话就是把模型的三角面细分成一组更小的面，再配合Displace贴图等信息进行处理。
Unity的Surface Shader支持Tessellation，例子如下

http://s11/mw690/001iGO8Ggy6YTyKE0qe7a&690

[例一：基本细分曲面]
http://s2/mw690/001iGO8Ggy6YTuHU5zj91&690
步骤
1：准备Displacement和Normal 两张贴图。Displacement根据亮度决定细分曲面的高度或者说凸起程度。
2：代码中添加
tessellate:tessFixed

    float _Tess;

            float4 tessFixed()
            {
                return _Tess;
            }
这个表示每个三角面细分的量级
3：对
Displacement进行纹理采样，并沿法线方向作相应偏移。

    void disp (inout appdata v)
            {
                float d = tex2Dlod(_DispTex, float4(v.texcoord.xy,0,0)).r * _Displacement;
                v.vertex.xyz += v.normal * d;
            }

Shader "Tessellation/1FixedAmount" {
Properties {
_Tess ("Tessellation", Range(1,32)) = 4
_MainTex ("Base (RGB)", 2D) = "white" {}
_DispTex ("Disp Texture", 2D) = "gray" {}
_NormalMap ("Normalmap", 2D) = "bump" {}
_Displacement ("Displacement", Range(0, 1.0)) = 0.3
_Color ("Color", color) = (1,1,1,0)
_SpecColor ("Spec color", color) = (0.5,0.5,0.5,0.5)
}
SubShader {
Tags { "RenderType"="Opaque" }
LOD 300
CGPROGRAM
#pragma surface surf BlinnPhong addshadow fullforwardshadows vertex:disp tessellate:tessFixed nolightmap
struct appdata {
float4 vertex : POSITION;
float4 tangent : TANGENT;
float3 normal : NORMAL;
float2 texcoord : TEXCOORD0;
};
float _Tess;
float4 tessFixed()
{
return _Tess;
}
sampler2D _DispTex;
float _Displacement;
void disp (inout appdata v)
{
float d = tex2Dlod(_DispTex, float4(v.texcoord.xy,0,0)).r * _Displacement;
v.vertex.xyz += v.normal * d;
}
struct Input {
float2 uv_MainTex;
};
sampler2D _MainTex;
sampler2D _NormalMap;
fixed4 _Color;
void surf (Input IN, inout SurfaceOutput o) {
half4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
o.Albedo = c.rgb;
o.Specular = 0.2;
o.Gloss = 1.0;
o.Normal = UnpackNormal(tex2D(_NormalMap, IN.uv_MainTex));
}
ENDCG
}
FallBack "Diffuse"
}

http://s6/small/001iGO8Ggy6YTyCZ4SF45&690

[例二：基于距离细分曲面]

http://s11/mw690/001iGO8Ggy6YTuHXwZI4a&690

基于相机距离进行细分，离相机越近细分面数越多。

       float4 tessDistance (appdata v0, appdata v1, appdata v2) {
                float minDist = 10.0;
                float maxDist = 25.0;
                return UnityDistanceBasedTess(v0.vertex, v1.vertex, v2.vertex, minDist, maxDist, _Tess);
            }

Shader "Tessellation/2Distance" {
Properties {
_Tess ("Tessellation", Range(1,32)) = 4
_MainTex ("Base (RGB)", 2D) = "white" {}
_DispTex ("Disp Texture", 2D) = "gray" {}
_NormalMap ("Normalmap", 2D) = "bump" {}
_Displacement ("Displacement", Range(0, 1.0)) = 0.3
_Color ("Color", color) = (1,1,1,0)
_SpecColor ("Spec color", color) = (0.5,0.5,0.5,0.5)
}
SubShader {
Tags { "RenderType"="Opaque" }
LOD 300
CGPROGRAM
#pragma surface surf BlinnPhong addshadow fullforwardshadows vertex:disp tessellate:tessDistance nolightmap
#include "Tessellation.cginc"
struct appdata {
float4 vertex : POSITION;
float4 tangent : TANGENT;
float3 normal : NORMAL;
float2 texcoord : TEXCOORD0;
};
float _Tess;
float4 tessDistance (appdata v0, appdata v1, appdata v2) {
float minDist = 10.0;
float maxDist = 25.0;
return UnityDistanceBasedTess(v0.vertex, v1.vertex, v2.vertex, minDist, maxDist, _Tess);
}
sampler2D _DispTex;
float _Displacement;
void disp (inout appdata v)
{
float d = tex2Dlod(_DispTex, float4(v.texcoord.xy,0,0)).r * _Displacement;
v.vertex.xyz += v.normal * d;
}
struct Input {
float2 uv_MainTex;
};
sampler2D _MainTex;
sampler2D _NormalMap;
fixed4 _Color;
void surf (Input IN, inout SurfaceOutput o) {
half4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
o.Albedo = c.rgb;
o.Specular = 0.2;
o.Gloss = 1.0;
o.Normal = UnpackNormal(tex2D(_NormalMap, IN.uv_MainTex));
}
ENDCG
}
FallBack "Diffuse"
}

http://s6/mw690/001iGO8Ggy6YTA5z63b55&690

[例三：边缘长度曲面]
http://s6/mw690/001iGO8Ggy6YTuI0Dzvf5&690
根据三角面的边缘长度进行细分，也就是越大的三角细分越多

    float4 tessEdge (appdata v0, appdata v1, appdata v2)
            {
                return UnityEdgeLengthBasedTess (v0.vertex, v1.vertex, v2.vertex, _EdgeLength);
            }

Shader "Tessellation/3EdgeLength" {
Properties {
_EdgeLength ("Edge length", Range(2,50)) = 15
_MainTex ("Base (RGB)", 2D) = "white" {}
_DispTex ("Disp Texture", 2D) = "gray" {}
_NormalMap ("Normalmap", 2D) = "bump" {}
_Displacement ("Displacement", Range(0, 1.0)) = 0.3
_Color ("Color", color) = (1,1,1,0)
_SpecColor ("Spec color", color) = (0.5,0.5,0.5,0.5)
}
SubShader {
Tags { "RenderType"="Opaque" }
LOD 300
CGPROGRAM
#pragma surface surf BlinnPhong addshadow fullforwardshadows vertex:disp tessellate:tessEdge nolightmap
#include "Tessellation.cginc"
struct appdata {
float4 vertex : POSITION;
float4 tangent : TANGENT;
float3 normal : NORMAL;
float2 texcoord : TEXCOORD0;
};
float _EdgeLength;
float4 tessEdge (appdata v0, appdata v1, appdata v2)
{
return UnityEdgeLengthBasedTess (v0.vertex, v1.vertex, v2.vertex, _EdgeLength);
}
sampler2D _DispTex;
float _Displacement;
void disp (inout appdata v)
{
float d = tex2Dlod(_DispTex, float4(v.texcoord.xy,0,0)).r * _Displacement;
v.vertex.xyz += v.normal * d;
}
struct Input {
float2 uv_MainTex;
};
sampler2D _MainTex;
sampler2D _NormalMap;
fixed4 _Color;
void surf (Input IN, inout SurfaceOutput o) {
half4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
o.Albedo = c.rgb;
o.Specular = 0.2;
o.Gloss = 1.0;
o.Normal = UnpackNormal(tex2D(_NormalMap, IN.uv_MainTex));
}
ENDCG
}
FallBack "Diffuse"
}

[例四： Phong细分曲面]

http://s1/mw690/001iGO8Ggy6YTuI35HW60&690

如果是low poly的模型的话，沿着法线方向去细分效果并不好。
http://s5/bmiddle/001iGO8Ggy6YTAaVuqE04&690

而我们可以用Phong Tesselation去细分，该方法尤其适用于low poly模型。

tessphong:_Phong
#pragma surface surf Lambert vertex:dispNone tessellate:tessEdge tessphong:_Phong nolightmap

Shader "Tessellation/4Phong" {
Properties {
_EdgeLength ("Edge length", Range(2,50)) = 5
_Phong ("Phong Strengh", Range(0,1)) = 0.5
_MainTex ("Base (RGB)", 2D) = "white" {}
_Color ("Color", color) = (1,1,1,0)
}
SubShader {
Tags { "RenderType"="Opaque" }
LOD 300
CGPROGRAM
#pragma surface surf Lambert vertex:dispNone tessellate:tessEdge tessphong:_Phong nolightmap
#include "Tessellation.cginc"
struct appdata {
float4 vertex : POSITION;
float3 normal : NORMAL;
float2 texcoord : TEXCOORD0;
};
void dispNone (inout appdata v) { }
float _Phong;
float _EdgeLength;
float4 tessEdge (appdata v0, appdata v1, appdata v2)
{
return UnityEdgeLengthBasedTess (v0.vertex, v1.vertex, v2.vertex, _EdgeLength);
}
struct Input {
float2 uv_MainTex;
};
fixed4 _Color;
sampler2D _MainTex;
void surf (Input IN, inout SurfaceOutput o) {
half4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
o.Albedo = c.rgb;
o.Alpha = c.a;
}
ENDCG
}
FallBack "Diffuse"
}

http://s13/mw690/001iGO8Ggy6YTBlelnmfc&690

参考资料：
Surface Shaders with DX11 Tessellation
Phong Tessellation

《Introduction_to_3D_Game_Programming_with_Directx_11》

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