The new FFT convolution bloom

[a_bad_rat]

Hi everybody. I’d like to discuss 4.16’s new FFT convolution bloom method. I couldn’t get it to work for a little bit but a recent preview update managed to fix it for me. Here’s some stuff:

@Stephen Ellis;693808

Post processing now supports Image-based (FFT) convolution for physically realistic bloom effects in addition to the existing bloom method. This new post processing feature is designed for use in cinematics or on high-end hardware.

• Image based Convolution adds new control parameters to the existing Lens | Bloom section found in Post Process volumes.

• In using a new texture to serve as the kernel image, it is important to ensure that the full image is present on the gpu and available at full resolution. Two settings are required to ensure this:

• Mips Gen Setting should be set to NoMipmaps

• Texture option Never Stream should be selected.

So here’s the normal bloom

http://i.imgur.com/dMNYSnZ.jpg

Here’s the default FFT bloom. There’s a very slight loss of sharpness.

http://i.imgur.com/2zaa5pJ.jpg

Here’s what happens when you resize the default Bloom Kernel down to 512 from 2048. (Note the drastic loss of sharpness)

http://i.imgur.com/dtf3jm6.jpg

Here’s what happened when I tried to create my own quick .EXR file to use as a texture and couldn’t get it to work properly.

http://i.imgur.com/7ISz9ma.jpg

Here’s the default engine Bokeh texture used as bloom.

http://i.imgur.com/M14plcS.jpg

In the end the only non-default acceptable result I managed to get was from resizing the default Bloom Kernel on Y and then putting it back onto a 2048 black texture.

http://i.imgur.com/tx8nkdg.jpg

If I could figure out how to generate .EXR files that work properly that’d be great, as this “anamorphic bloom” effect is one I’ve been trying to figure out for a while now. Anybody else experimented with this?