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Thread: Tessellation -> very begginner question

  1. #1
    Newbie Newbie
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    Sep 2014
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    Tessellation -> very begginner question

    Hello, I'm trying to follow the code explained on OpenGL superbible book...

    ..there is a basic code for tessellation demonstration, it have to figure out a triangle through VertexShader -> TessellationControlShader -> TessellatioEvaluationShader -> FragmentShader.

    The triangle at the must be filled with a lot of subtriangle...

    ..the way to figure it out is to call :

    glDrawArrays(GL_PATCHES,0,3);

    What happen is an empty window...and i get an exception : "GL_INVALID_ENUM error generated. Invalid primitive mode."

    if i call the following : glDrawArrays(GL_TRIANGLES,0,3); it shows a simple triangle but it is not filled with tessellation.

    I'm working with OpenGL version 3.3.0, is there a reason for this behavior?

    Sorry for my stupid beginner question.

  2. #2
    Newbie Newbie
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    Sep 2014
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    I'm new myself, but I believe that tessellation was added in 4.0. https://www.opengl.org/sdk/docs/man3...DrawArrays.xml does not mention GL_PATCHES.

  3. #3
    Senior Member OpenGL Pro Aleksandar's Avatar
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    Jul 2009
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    1,214
    That is not a belief. A HW tessellation is not possible in OpenGL 3.3. You need to buy new hardware if you want to play with it.

  4. #4
    Newbie Newbie
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    Sep 2014
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    Thanks everybody for the answers...i have a book that show all samples with opengl 4.0....and now i have to upgrade my hardware :-( ... Thanks again.

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