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I've got the book "OpenGL SuperBible Seventh Edition" and I'm now wondering how the tesselation works? I'm currently in chapter 3 of the book and I do not really understand the explanation of the tesselation with the tesselation control shaders, the tesselation engine and the tesselation evaluataion shaders.

So I'm using

  • OpenGL 4.5
  • C++11
  • Windows

Can anyone explain to me in detail how tesselation works in OpenGL 4.5 and what control points, batches etc. are?

EDIT: Ok, I think I have to ask in more detail.

  • What is an "high-order primitive"?
  • What are "quadrilaterals"?
  • What are those "control points" from which a patch is formed?
  • What are "batches"? (The book explains that the tesselation control shader runs in batches on groups of control points where the size of each batch is the same as the number of vertices per patch.)
  • What is a "barycentric coordinate".

I think that makes it more clear what my problem and question is.

ShadowDragon
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  • I don't own that book, but isn't it that book's job to teach you what those things mean? Doesn't it go over "how tesselation[sic] works" and the meaning of the various other terms? – Nicol Bolas Jul 30 '16 at 17:18
  • Yeah, it is the book's job to teach me what those things mean and the book does it. The problem I'm having is that I don't understand the tesselation part of this book. It might be because I'm not a native english speaker or because the way how that part of the book is written. So that's why I am asking here. Because I don't understand the explanation in the book. – ShadowDragon Jul 30 '16 at 23:18
  • The problem with your question is that it's very broad and general. I have no idea what it is about tessellation that you don't understand. It sounds very much like you're asking someone to [rewrite this page, and its associate pages,](https://www.opengl.org/wiki/Tessellation) for you. We generally don't do that sort of thing on SO; we try to deal with focused questions, not broad "how does this entire system work" kinds of things. – Nicol Bolas Jul 30 '16 at 23:25
  • "Tessellation" means a lot of different things. I suggest a scientific approach. Start with the first example in the book, write the code, see what it does. Try changing a number and see what happens. Change a shader... – Hugh Fisher Jul 31 '16 at 00:37

1 Answers1

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The 6th edition SuperBible has a cubic Bezier patch example, which I'm guessing will still be in the 7th. Using that to answer your questions

High order primitive: anything more complicated than a triangle. In this case a Bezier patch. Quadrilateral: 4 vertices forming flat polygon Control points: the 4x4 = 16 vertices forming a single Bezier patch Batch: the Bezier patch. Barycentric coordinate: not important

Computer graphics is a subject where you can always see the results of what you do. I suggest less thinking, more coding.

Hugh Fisher
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