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Thread: Glow / blur / trails ?

  1. #1
    Junior Member Newbie
    Join Date
    May 2007

    Glow / blur / trails ?

    I cant seem to find out what its called but what I'm trying to accomplish is the glowing/blur effect on an object. Like a circle that is glowing and when moved it will give off a trail or hue. kind of like the Solorwinds Screen saver

    Any ideas what its called and how i can achieve this?

  2. #2
    Senior Member OpenGL Pro Zengar's Avatar
    Join Date
    Sep 2001

    Re: Glow / blur / trails ?

    Render the objects multiple times over different positions, while increasing the alpha value. The current position will have the alpha value of 1.0 (fully opaque).

  3. #3
    Junior Member Newbie
    Join Date
    May 2007

    Re: Glow / blur / trails ?

    another good way to accomplish this effect if you want it for all of your objects as your screenshot shows is to:

    do your rendering, then copy the screen to a texture
    then on subsequent renders, draw the copied texture over the screen at some alpha before doing your next rendering

  4. #4
    Super Moderator OpenGL Guru imported_dorbie's Avatar
    Join Date
    Jul 2000
    Bay Area, CA, USA

    Re: Glow / blur / trails ?

    You're looking for "motion blur" there are many ways but it's generally expensive and so it is usually approximated of done incorrectly.

    The accurate way is to integrate all positions between the last frame and this.

    Zengar's suggestion does not accomplish this because the recent frame has a weight of 1.0, ziggle's suggestion does not accomplish this because it convolves inter frame and not intra frame.

    Either or a combination of their suggestions may provide something that looks 'cool' heck it might even be closer to what you're looking for than true motion blur.

    Good luck.

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