Improving Tesselation Resolution

[nick.ace]

Does anyone know how to write tesselation shaders? I looked at the example, and was able to integrate it with my custom shader, but the control and evaluation shaders from diffuse-normal-specular-tess.shader doesn't really seem to do anything. I want to be able to take a triangle and subdivide it into an arbitrary amount of triangles. There seems to be a lack of tutorials online for tesselation shaders .

[Rastar]

Well, you can't divide a triangle into an arbitrary number of triangles, because the tessellation factors are limited (iirc factors of 64 are guarantueed, more might be available). But usually that's sufficient. A good approach often is to calculate the tessellation factors based on the screen-space size of the triangle edge. That way the tessellation automatically changes based on the distance from the camera. Here is an example

 

http://codeflow.org/entries/2010/nov/07/opengl-4-tessellation/

 

The author's doing that for terrain tessellation, but the principle is the same.

[nick.ace]

Thanks! I found a link at the bottom of the page that explained it better. I didn't know what the outer and inner tess levels were and how they are used. I'm not interested in doing dynamic tesselation right now, but maybe I'll implement that later.

[Rastar]

Which reminds me: Ages ago I did a couple of blog posts here a bout tessellation

 

http://www.leadwerks.com/werkspace/blog/117/entry-1185-pass-the-tessellation-please-part-1/

http://www.leadwerks.com/werkspace/blog/117/entry-1195-pass-the-tessellation-please-part-2/

 

Maybe there's something helpful in there as well.

[nick.ace]

Thanks! Those tutorials you wrote are super helpful! I kind of wish I saw them earlier because those are some of the best tutorials I've seen on the subject.

 

Btw, I actually got it working yesterday. I guess I thought there was more control you could have over the shaders than just the number of subdivisions you could have and how you want the subdivisions to behave (to an extent). I was able to make shattering windows because of it lol.