color problem

This is a discussion on color problem within the Game Programming forums, part of the General Programming Boards category; Hello! I use vertex-colors in my 2D elements of my program. I thought I understood the what the color is, ...

  1. #1
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    color problem

    Hello!
    I use vertex-colors in my 2D elements of my program.
    I thought I understood the what the color is, but it seems I don't. I thought the color consists of RGB values: RRGGBB. So that 0000ff is blue, 00ff00 is green and ff0000 is red. These colors seem to work, but when I combine them something goes wrong. ffffff which should be white is something like this and ffff00 which should be bright yellow is actually like this.

    What's wrong with it?

  2. #2
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    And what happens instead? We can probably figure out what is wrong if you give us a short table of
    Code:
    Value   Expected    Actual
    where "Value" might be 00FF00, and Expected "Green", and Actual "Blue".

    --
    Mats
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    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
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    Code:
    Value   Expected   Actual
    ffffff   white   this
    ffff00   this this
    00ffff   this this
    ff00ff   this this
    It's no point to give more colors. It seems that all colors are darker and I can't give exact colors anyway.

  4. #4
    Frequently Quite Prolix dwks's Avatar
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    Are you storing the colour numbers in a wide enough type? If you stuff "0xff" into a char, for example, you might not get the results you're expecting. An unsigned char would work; or, if you're putting all of the data into one variable, an unsigned long (or unsigned int if you wish I guess).

    Beyond that, you might want to post some relevant code.
    dwk

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  5. #5
    Super Moderator VirtualAce's Avatar
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    White is not FFFFFF. It is FFFFFFFF.

    Most color is expressed as RGBA, ARGB, or XRGB. What you have expressed is XRGB. If you are in a graphics API and you have alpha blending enabled but set alpha to 0.0f you will not get any colors at the vertices.

  6. #6
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    OK, I forgot about alpha, because I don't use it. These colors are for rhw vertices. Nevertheless it seems to make no difference. It seems that ffffff and ffffffff give exactly the same result and the problem remains.

    I use DWORDs to store colors.

  7. #7
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    It seems I know the problem now.
    D3DPRESENT_PARAMETERS :: EnableAutoDepthStencil

    When it is set to TRUE as in 3D it does weird things. I use 3D and 2D rhw simultaneously so I somehow need to change it, but it is not that simple, because it's used in CreateDevice. What should I do? Should I use two separate DirectX devices or is there some other way?

  8. #8
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    Never mind the previous post, that wasn't the problem.
    The problem was, that I had to unset the texture, so the 2D elements used the colors of the previously set textures. Colors turned darker, because the texture's color was brown.
    Problem solved!

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