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Thread: Converting OpenGL to OpenGLES?

  1. #1
    Junior Member
    Join Date
    Jul 2008
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    1

    Converting OpenGL to OpenGLES?

    Hi

    I've been doing OpenGL for a few years, but am struggling under OpenGL ES with all the missing commands (glTexGen at the mo for example). Is there a way of doing all the stuff OpenGL does under OpenGL ES? Is there an online guide somewhere or a book that's recommended to help us learn the differences and how to handle them?

    Also, is there a way to projected textures under OpenGL ES? (Obviously without glTexGen etc)?

    Any help would be greatly appreciated.

    Thanks!

  2. #2
    Senior Member
    Join Date
    May 2006
    Posts
    353

    Re: Converting OpenGL to OpenGLES?

    Quote Originally Posted by Useless
    Is there a way of doing all the stuff OpenGL does under OpenGL ES?
    OpenGL ES provides only a subset of the OpenGL functionality so there are some things you can't do (unless you implement them yourself), such as glBegin/End, wireframe, two-sided materials, and texgen.

    Also, is there a way to projected textures under OpenGL ES? (Obviously without glTexGen etc)?
    Both EYE_LINEAR and OBJECT_LINEAR texgen modes can easily be implemented using the texture matrix, and re-using the same vertex data array for both positions and texcoords. Simply use the plane coefficients you pass as OBJECT_PLANE for each of the texcoord components as a row of the texture matrix.

    Note however that some OpenGL ES implementations don't perform perspective correct interpolation with projected texture coordinates (i.e. where Q != 1).
    Georg Kolling, Imagination Technologies
    Please ask questions specific to PowerVR hardware or SDKs on the PowerVR Insider Forum
    DevTech@imgtec.com | http://www.powervrinsider.com

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