Bloom with Alpha environment? Possible?

JasonWNalley

So, I am trying to render a Star Wars inspired figure with a Light Sword, and I never liked the way DAZ Light swords looked with their multiple layers of transparent blades... the effect doesn't have that soft edge that a bloom does.. So I was wondering if it's possible to have the bloom show up in a render with no environment to speak of (except a shadow catcher floor)  I've tried a few ways, but without some sort of mass behind it (semi-transparent works) I can't seem to get the boom effect to render out.  Anyone know any tricks?

juvesatriani

Hi.. In my experiences , Bloom is POST FX which added  after renderng process done .t does "smearing/blur/bleeding" area around it to get what we know as bloom .

So with alpha environment , the post FX will not getting right information about area around the object which should have those fx . Especially if you have plan to mashup with another render/photo

Something you can try is doing Beauty pass for  any emission shaders in your scene.

Then bring into 2D image editor . Overaly in top your standard render .

Set layer mode to screen or linear dodge - give it blur filter with low setting - duplicate it then give them blur filter again , now with bigger value than before - repeat the steps until you see the bloom FX you liike

JasonWNalley

juvesatriani said:

Hi.. In my experiences , Bloom is POST FX which added  after renderng process done .t does "smearing/blur/bleeding" area around it to get what we know as bloom .

So with alpha environment , the post FX will not getting right information about area around the object which should have those fx . Especially if you have plan to mashup with another render/photo

Something you can try is doing Beauty pass for  any emission shaders in your scene.

Then bring into 2D image editor . Overaly in top your standard render .

Set layer mode to screen or linear dodge - give it blur filter with low setting - duplicate it then give them blur filter again , now with bigger value than before - repeat the steps until you see the bloom FX you liike

In the IRay render settings, there is a bloom filter.  If you enable this, you can achieve different levels of bloom on emissive objects, lights, and reflections.  In reality, what we know as 'blooming' occurs due to fine particulates in the air, and has no reliance on something to be behind it to be visible.  However, when using the bloom filter in an entirely alpha environment the bloom doesn't show up.  If you put a plane behind it, or an object behind it, then the bloom appears.  What you're suggesting can be done with a simple "outer glow" in photoshop on the light sword, and currently, if I want that bloom effect that's how I have to do it, or I have to create a volumetric light catcher in the scene (this doesn't look as smooth, unfortunately).

These examples are PNGs coming straight out of DAZ with no post-processing of any kind.
Alpha Environment:

Simple Plane behind actor:

With a background:

 

The goal, for me, is to capture both the bloom and the shadow in a render, without any background objects (in an alpha environment) without having to resort to post-processing to re-create the bloom (which never looks like it's supposed to).  The closest I've come is by taking a cue from some of the other non-daz light sabers that work in DAZ, which have employed the use of a pair or trifecta of planes to create a volumetric light catcher around the blade.  Though this comes with its own set of problems (edges that need cleaning even with an opacity mask).  

I'm hoping someone has an answer... I've been trying various things, with limited success...