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Type: Posts; User: memfr0b

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  1. Replies
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    Re: Coping with the blank screen of death.

    You did not provide texture coordinates for your vertices. That means, both vertices will use whatever tex coord was set before (probably the default (0,0,0,1)), which will map to the texelat index...
  2. Re: Wrapping a OpenGL Texture from a SDL_Surface does not work

    You never disable texturing, so after loading the texture, not only is your quad textured, but so are your lines. Commenting out the glTexImage2D call helps because without the call the texture...
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    Re: problem compiling/linking on linux

    The messages aren't generated because some libs aren't used, but because you're using link flags during compilation. Compilation (transforming source code to binary code) and linking (combining...
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    Re: problem compiling/linking on linux

    The first error (and probably some of the following) is caused by a typo in the type name. The correct type is GLfloat (notice the uppercase L), not Glfloat.

    The invalid suffix errors are caused...
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    Re: How to compute the matrix used by gluLookAt

    The up vector is recomputed to guarantee an ortho-normal coordinate system. The up vector provided to gluLookAt isn't necessarily orthogonal to the view vector, but the one used to build the...
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    Re: multipass-multitexturing problem

    No, you misunderstood. It is possible to combine multiple passes, it's just that when you have more than one texture per pass, you need to use different texture environments and blend functions.
    ...
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    Re: multipass-multitexturing problem

    When you're switching from multipass to multitexture+multipass, you have to be careful to choose the correct texture environment functions to achieve the same end result. I'll demonstrate what i...
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    Re: Quick shading/shadowing question

    For lighting purposes, the surface normal specifies the orientation of the surface and thus controls the intensity of the reflected/scattered light by the surface.

    OpenGL doesn't compute surface...
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    Re: special line rendering

    Polygon offset affects lines too. You just have to enable is separately with glEnable(GL_POLYGON_OFFSET_LINE).
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    Re: A few basic questions on OpenGL

    You can achieve this by using culling and drawing in two steps:

    Again, you need to draw in two steps. The polygon offset is necessary because lines and polygons are rasterized differently, which...
  11. Thread: vvector.h

    by memfr0b
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    Re: vvector.h

    Assuming that each float[4] contains a column of the matrix, both types are actually compatible. You could just use float temp[4][4] in you program and and pass &temp[0][0], temp[0] or (float*)temp...
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    Re: Where is the type FILE?

    FILE (and the related functions) are part of the C standard library and are defined in stdio.h.
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    Re: Changing texture filtering on the fly?

    Anisotropy is an additional functionality which reduces the blur introduced by trilinear filtering when looking at a surface at a steep angle. See Wikipedia - Anisotropic filtering for more...
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    Re: gluPerspective and glFrustum...

    The functionality of gluPerspective is a strict subset of glFrustum. It does not include rotation, and exactly the same amount of translation as glFrustum. You're probably thinking of gluLookAt.
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    Re: Changing texture filtering on the fly?

    GL_LINEAR_MIPMAP_LINEAR is what is called trilinear filtering.

    GL_NEAREST_MIPMAP_NEAREST is nearest neighbor filtering using the best matching mipmap.

    GL_LINEAR_MIPMAP_NEAREST is linear...
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    Re: Display list problem

    Think about what display lists actually do:

    Reduce number of function calls.
    Instead of calling glColor/glNormal/glVertex/etc many times, you only call glCallList once. Store data in...
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    Re: Changing texture filtering on the fly?

    The code is perfectly fine. You can change the minifacation/magnification settings (almost) any time you like. They will stay until you change them again.

    The only thing you have to keep in mind...
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    Re: Render to Texture issue (SDL+OpenGL)

    Heh, thanks for the flowers :) Nice to hear it worked.

    If you want to mention my minor contribution to your project, sure, the name "memfr0b" is fine. My website is http://memfrob.de , ...
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    Re: light position problem

    glutSolidTeapot seems to fiddle with the current matrix. You have to switch to GL_MODELVIEW for it to work correctly.
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    Re: Render to Texture issue (SDL+OpenGL)

    You're currently using a single blend function for both color and alpha. With glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA), the alpha value does not add up, but is averaged between source and...
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    Re: Render to Texture issue (SDL+OpenGL)

    The problem with the black borders around your brush stems from texture filtering. The problem is caused by putting a white circle on black backgroud. Even though the background has alpha = 0, and...
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    Re: GLUT: glutKeyboardFunc + glutSpecialFunc

    Special key codes overlap with ascii character codes. For example GLUT_KEY_LEFT has the same code as the character 'd'.
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    Re: glutInit conflicts with fstream output

    Output may be buffered until you explicitly flush the buffers or close the file. Try calling the flush() method after outputting your data.
  24. Re: Getting Z coordinates from 3 vectors knowing their X, Y coordinates

    (3, 3, -3) and (4, -4, -4) are not perpendicular.


    3*4 + 3*(-4) + ((-3)*(-4)
    = 12 - 12 + 12
    = 12Let's try a different example:


    a = (0, 2, z1)
    b = (0, -3, z2)
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    Re: glScale/depth test

    First off, there's simply a conceptual difference between "Which type of faces should be culled" and "Which vertex order indicates front-facing polygons". Having both functions allows you to...
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