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Thread: OpenGL|ES 1.0 sample are not support Fixed-point

  1. #1
    Junior Member
    Join Date
    May 2005
    Posts
    1

    OpenGL|ES 1.0 sample are not support Fixed-point

    I'v trace the codes of OpenGL|es 1.0 sample and found that although it has fixed function like translatex() ...,but actually when fixed-point value pass to the function, the value conver back to float to count,as follow:

    glScalex(GLfixed x, GLfixed y, GLfixed z) {
    __gl_matrixf_t m;
    __gl_mk_identity(m);

    //__GL_X_2_F mean fixed to float
    __M(0,0) = __GL_X_2_F(x); //here!
    __M(1,1) = __GL_X_2_F(y); //here!
    __M(2,2) = __GL_X_2_F(z); //here!
    __gl_update_mtx(m);
    }

    so ? since OpenGL|ES is support fixed-point why it happened ? Where can I find the real OpenGL|es which support fixed-point?
    Thank for your attention...thank you very much!

  2. #2
    Junior Member
    Join Date
    Oct 2004
    Location
    UK
    Posts
    24

    Re: OpenGL|ES 1.0 sample are not support Fixed-point

    Are you talking about the behaviour of OGLES wrappers ? Most of those will probably map Fixed Point into Floating Point ASAP for ease of implementation, this does mean you can not necessarily see the true impact of the loss of accuracy which can occur when using fixed point maths.

    One option is to move to a real fixed point device with OGLES support such as the Dell AximX50v which only supports fixed point entry points, or alternatively implement your own fixed point maths and only pass the data onto the wrapper at the last moment for rendering.

    K-

  3. #3
    Senior Member
    Join Date
    Sep 2003
    Location
    Seattle, WA
    Posts
    246

    Re: OpenGL|ES 1.0 sample are not support Fixed-point

    Or, in case you are looking for sources, there is Vincent Mobile 3D Rendering Library.

    - HM

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