![]() ![]() If you look at a completed tessellation, you will see the original motif repeats in a pattern. The term has become more specialised and is often used to refer to pictures or tiles, mostly in the form of animals and other life forms, which cover the surface of a plane in a symmetrical way without overlapping or leaving gaps. They were used to make up 'tessellata' - the mosaic pictures forming floors and tilings in Roman buildings The word 'tessera' in latin means a small stone cube. When you fit individual tiles together with no gaps or overlaps to fill a flat space like a ceiling, wall, or floor, you have a tiling. Patch.vertex * barycentricCoordinates.x + patch.vertex * barycentricCoordinates.A tessellation is created when a shape is repeated over and over again covering a plane without any gaps or overlaps.Īnother word for a tessellation is a tiling. ![]() The X, Y, and Z coordinates determine the weights of the first, second, and third control points. To find the position of this vertex, we have to interpolate across the original triangle domain, using the barycentric coordinates. įloat3 barycentricCoordinates : SV_DomainLocation Inside the function, we have to generate the final vertex data. OutputPatch patch, float3 barycentricCoordinates : SV_DomainLocation They have the SV_DomainLocation semantic. To make this possible, the domain function is invoked once per vertex and is provided the barycentric coordinates for it. It's up to the domain shader to use those coordinates to derive the final vertices. Instead, it comes up with barycentric coordinates for those vertices. While the tessellation stage determines how the patch should be subdivided, it doesn't generated any new vertices. TessellationFactors factors, OutputPatch patch The domain program is fed the tessellation factors that were used, as well as the original patch, which is of type OutputPatch in this case. We signal this again via the UNITY_domain attribute. Shader "Custom/Tessellation" īoth the hull and domain shader act on the same domain, which is a triangle. Duplicate that shader, rename it to Tessellation Shader and adjust its menu name. ![]() To clearly see that triangles get subdivided, we'll make use of the Flat Wireframe Shader. Let's put the code that we'll need in its own file, MyTessellation.cginc, with its own include guard. The first step is to create a shader that has tessellation enabled. ![]() We're going to need a hull program and domain program. But it's not as simple as adding just one other program to our shader. This stage sits in between the vertex and the fragment shader stages. We cannot control that, but there's also a tessellation stage that we are allowed to configure. It does this for various reasons, for example when part of a triangle ends up clipped. The GPU is capable of splitting up triangles fed to it for rendering. This makes it possible to add more details to geometry, though in this tutorial we'll focus on the tessellation process itself. In our case, we're going to subdivide triangles so we end up with smaller triangles that cover the same space. Tessellation is the art of cutting things into smaller parts. If you don't have enough triangles, make some more. This tutorial is made with Unity 2017.1.0. It uses the Flat and Wireframe Shading tutorial as a basis. This tutorial covers how to add support for tessellation to a custom shader. ![]()
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