Bloom Haze on Neutral and Dark Tones

Started by WAS, July 08, 2018, 01:09:55 AM

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WAS

Here is an example of Bloom Haze on neutral and dark tone colours with bloom at 0.1. Colour is at 0.1 with some fake stones for highlights. There should be NO bloom here at these colours levels and lighting level, with no specular.

Haze is especially noticeable in shadows, but exists in the whole frame.

As you may be familiar with differance comparison shows any changes in pixel tone and colour.

It would be nice if the bloom feature was simply a levels input, and pixel blur radius for custom blooms to fit individual scenes without post. Maybe even a button for the preview to visualize what it may look like by applying to preview. Similar to toggling DOF visualization or other stuff.

WAS

#1
Here is a shape example with extended shadows, and even colours within shadows effected. This image in most bloom filters actions I have in PS has  some bloom, but not in the shadows, where TG effects shadows and just overall the whole frame. I bet even if I stilled these in UE4 it would act appropriately.

You'll notice even darker tones bloom onto lighter tones (base of the shape lift) which is just odd, instead of it being only the other way around mainly in effect

Matt

#2
It is supposed to simulate a small amount of diffusion by the lens and possibly other reflections within the camera, and these are optical effects don't change according to luminance. So it works like this by design. Perhaps bloom isn't the best name for this, as the term bloom can mean other phenomena that happen at the film or sensor which do change according to luminance, and which Terragen doesn't do.

I think 0.1 gives a stronger effect than you'd see with most cameras, but I wanted the default to be high enough to cause a noticeable difference when you first enable it.

Most cameras also push the shadows down a little bit more than TG's default tone mapping, so combining TG's bloom with some levels/curves adjustments in post (or increasing contrast in TG) sometimes looks pretty good.

Our 2018 roadmap includes realtime previews/adjustments of TG's post effects and tone mapping in the Render View.

Matt
Just because milk is white doesn't mean that clouds are made of milk.

WAS

I see. Yeah, bloom might not be the best name. I have worked with hundreds of bloom shaders, filters, and macros for programs and some of them being pretty high quality and incorporating math I don't understand from the authors but never seen these effects. They almost look based on high pass computation and changing the saturation with some blurring or something similar. All in all it is a cool effect, and like noted in the Doc's topic, has a very dreamy effect. In early versions of DX this is how bloom worked in general as it was based on contrast and brightness rather than actually tone mapping the buffers level and clamping to specular and strong light surfaces. 

Quote from: Matt on July 09, 2018, 06:00:30 PM
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Most cameras also push the shadows down a little bit more than TG's default tone mapping, so combining TG's bloom with some levels/curves adjustments in post (or increasing contrast in TG) sometimes looks pretty good.

Our 2018 roadmap includes realtime previews/adjustments of TG's post effects and tone mapping in the Render View.

Matt

Yeah, simple curves in the middle pushed down a bit makes stills really pop.

The rtp for post effects will be so nice. Save a lot of time or doing silly little crops to see effects.

Though again, a input control for levels of the effect would allow control of the bloom to certain light levels by clamping in blacks/mid-tones etc.