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I have searched the net for resources related to rendering a bloom effect using GLSL, but haven't found anything. Although the tutorial at Philip Rideout's website is a good one, it performs very poorly on my Nvidia GPU.

Can anyone guide me as to how should I approach this problem and build a fairly efficient implementation of a bloom effect?

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    \$\begingroup\$ Ardor3d, an opensource java 3d engine, has a bloom shader implemented. Since it is opensource you can easily check that out (www.ardor3d.com). But basically, its just copying the framebuffer, downscale,blur,additive blending.. \$\endgroup\$
    – Pjotterke
    Commented Oct 18, 2011 at 14:39
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    \$\begingroup\$ What kind of GPU do you have? \$\endgroup\$
    – user1430
    Commented Oct 18, 2011 at 15:03
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    \$\begingroup\$ Very important to let us know what GPU / video card you have. +! @JoshPetrie \$\endgroup\$ Commented Oct 18, 2011 at 15:29
  • \$\begingroup\$ I have a Nvidia GeForce GT 230M graphic card on my laptop \$\endgroup\$
    – snape
    Commented Oct 18, 2011 at 15:35
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    \$\begingroup\$ @snape: How large a gaussian kernel are you using, and what is the resolution of your largest blurred FBO? The easiest way to improve performance is to use a smaller kernel and a smaller FBO. (In my stuff, I do my blurring inside a 512x512 resolution FBO, no matter the display resolution) \$\endgroup\$ Commented Oct 18, 2011 at 20:52

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As Trevor mentioned in his comment, your only option might be to reduce the size of your kernel or to perform further downsampling .

But did you thoroughly read the tutorial you've linked to? There's a tip about exploiting hardware filtering, that the author calls the "sneaky" version. It's probably the best trick you can use to optimize you bloom effect without affecting its quality.

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  • \$\begingroup\$ Yes, I read the tutorial thoroughly. I finally improved it's performance by using offline rendering and also I hadn't enabled hardware support for graphics application earlier. \$\endgroup\$
    – snape
    Commented Apr 6, 2012 at 16:14
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I solved a very similar problem (blurring, but the bloom filter is bluring) with two passes.

In the first pass i blur in the X direction and in the second pass i blur in the Y direction.

I dunno from where i do have this trick but it lowers the time complexity from n² to 2n.

This works only for kernels which don't have any direction (so you can'T optimize a bokeh kernel this way).

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