In the Built-in Render PipelineA series of operations that take the contents of a Scene, and displays them on a screen. Unity lets you choose from pre-built render pipelines, or write your own. More info
See in Glossary, Surface ShadersA streamlined way of writing shaders for the Built-in Render Pipeline. More info
See in Glossary have some support for DirectX 11 / OpenGL Core GPU Tessellation.
tessellate:FunctionName
modifier. That function computes triangle edge and inside tessellation factors.vertex:FunctionName
) is invoked after tessellation, for each generated vertex in the domain shaderA program that runs on the GPU. More infoSurface Shaders have support for simple tessellation and displacement. When you write custom Shader programs, you can use the full set of DX11 shader model 5.0 features, including geometry, hull, and domain Shaders.
Current limitations of tessellation support:
Feature name | Universal Render Pipeline (URP) | High Definition Render Pipeline (HDRP) | Custom SRP | Built-in Render Pipeline |
---|---|---|---|---|
Surface Shaders | No For a streamlined way of creating Shader objects in URP, see Shader Graph. |
No For a streamlined way of creating Shader objects in HDRP, see Shader Graph. |
No | Yes |
If your model’s faces are roughly the same size on screen, add a fixed amount of tesselation to the MeshThe main graphics primitive of Unity. Meshes make up a large part of your 3D worlds. Unity supports triangulated or Quadrangulated polygon meshes. Nurbs, Nurms, Subdiv surfaces must be converted to polygons. More info
See in Glossary (the same tessellation level over the whole Mesh).
The following example script applies a fixed amount of tessellation.
Shader "Tessellation Sample" { 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 #pragma target 4.6 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" }
In the example above, the tessFixed
tessellation function returns four tessellation factors as a single float4 value: three factors for each edge of the triangle, and one factor for the inside of the triangle.
The example returns a constant value that is set in the Material properties.
You can also change tessellation level based on distance from the cameraA component which creates an image of a particular viewpoint in your scene. The output is either drawn to the screen or captured as a texture. More info
See in Glossary.
For example, you could define two distance values:
Shader "Tessellation Sample" { 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 #pragma target 4.6 #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" }
Here, the tessellation function takes the vertex data of the three triangle corners before tessellation as its three parameters.
Unity needs this to compute tessellation levels, which depend on vertex positions.
The example includes a built-in helper file, Tessellation.cginc, and calls the UnityDistanceBasedTess
function from the file to do all the work. This function computes the distance of each vertex to the camera and derives the final tessellation factors.
Purely distance based tessellation is effective only when triangle sizes are quite similar. In the image above, the GameObjectsThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary that have small triangles are tessellated too much, while GameObjects that have large triangles aren’t tessellated enough.
One way to improve this is to compute tessellation levels based on triangle edge length on the screen. Unity should apply a larger tessellation factor to longer edges.
Shader "Tessellation Sample" { 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 #pragma target 4.6 #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" }
In this example, you call the UnityEdgeLengthBasedTess
function from Tessellation.cginc to do all the work.
For performance reasons, call the UnityEdgeLengthBasedTessCull function instead, which performs patch frustum culling. This makes the shader a bit more expensive, but saves a lot of GPU work for parts of meshes that are outside of the Camera’s view.
Phong Tessellation modifies positions of the subdivided faces so that the resulting surface follows the mesh normals a bit. It’s quite an effective way of making low-poly meshes become more smooth.
Unity’s surface shaders can compute Phong tessellation automatically using tessphong:VariableName
compilation directive. Here’s an example shader:
Shader "Phong Tessellation" { 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" }
Here is a comparison between a regular shader (top row) and one that uses Phong tessellation (bottom row). See that even without any displacement mapping, the surface becomes more round.
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