iRAY emissive shader + visible glow - How?

SnapperTrx

So I am using the iRAY emissive shader on an object in my scene and althought it casts light I would like for it to have a visble glow to it. I have tried usin the Bloom Filter, but this adds a haziness to the entire scene, which is not what I am going for. Unfortunately the reference guide doesnt have much information on the Bloom Filter and it's uses, so I am at a bit of a loss. Any suggestions? Thanks.

BeeMKay

http://sickleyield.deviantart.com/journal/Tutorial-Creating-Dust-And-Atmosphere-in-Iray-522291773

try placing a small fog-box in front of your light. As far as I am aware, that is the only way to create a reach-out glow effect.

Tobor

"Glow" is up to interpretation, but do try the bloom filter in Iray. Turn it on, and do some spot renders while modifying the three options. You should also see the effect pretty well by switching to Iray render in the viewport (the little icon to the left of the camera selector, upper-right corner -- this assumes the standard interface).

These settings are just for starters. They will still need some tweaking:

http://docs.daz3d.com/lib/exe/fetch.php/public/software/dazstudio/4/new_features/4_8/bloomsettings2.png

 

SnapperTrx

Tobor said:

"Glow" is up to interpretation, but do try the bloom filter in Iray. Turn it on, and do some spot renders while modifying the three options. You should also see the effect pretty well by switching to Iray render in the viewport (the little icon to the left of the camera selector, upper-right corner -- this assumes the standard interface).

These settings are just for starters. They will still need some tweaking:

http://docs.daz3d.com/lib/exe/fetch.php/public/software/dazstudio/4/new_features/4_8/bloomsettings2.png

 

This is a great resource, thanks a lot!

rol3d

Glow in render works great on the entire scene, however I just want one object to glow. I have a lightbulb; all I want is for the filament to glow, but with render-glow, the entire bulb glows.

 

Any suggestions? Thanks.

Fishtales

If you can isolate the filament in the scene tab and the surface tab then add the emissive shader to it and it will glow as a light. Adjust the temperature and lumens to get the glow you need.

rol3d

Fishtales said:

If you can isolate the filament in the scene tab and the surface tab then add the emissive shader to it and it will glow as a light. Adjust the temperature and lumens to get the glow you need.

Thanks. I've got that part working just fine; the filament is 'emitting' quite nicely, even lighting up what's around it as it should But it needs to bloom in addition.

rol3d

Here are the examples (I didn't bother to let the renders finish, you can see the issue clearly).

The only difference between the two renders is 'Glow' is on for the bottom one. That amount of glow for the filament is what I want ... just not on the entire scene. I would like to do this without any postwork.

 

Thanks.

 

rol3d

Fishtales

Getting it to do that has something to do with the bloom threshold and the firefly nominal luminance settings. I did it on another render by trial and error by setting them so that only a certain light temperature was being affected. I'm sorry I can't be more specific as I try things randomly until something works but a lot of it doesn't work every time on all renders 

Tobor

rol3d said:

Glow in render works great on the entire scene, however I just want one object to glow. I have a lightbulb; all I want is for the filament to glow, but with render-glow, the entire bulb glows.

Three ways, all of them fairly easy, though all three require combining images in Photoshop, GIMP, or other graphics program:

1. Render it twice, and in Photoshop, apply a layer mask to the bloomed image. Isolate just the lamp on this layer.

2. Click off everything in the Scene tab except your lamp, and render it separately with the bloom as high as you want.

3. Use the canvas feature, and select the lamp as a node. Render just the node. Be sure to half the Alpha option turned on. The benefit of this approach is that the shadow and ocluding effects of other objects are preserved. In other words, if your character is holding the bulb with his hand, the part of the bulb blocked by fingers will be transparent (won't render). This makes compositing much easier. Do a Google search here for rendering nodes on Iray canvases.

Fishtales

After reading your post I decided to do a render with a set I was rendering at the time. I used the method I outlined in my post above. It still needs a bit more work and this is only 50% done but I thought I would post it here for you to see.

Click on image for full size.

Connatic

I like doing magic and energetic effects.  All glows are in-render and I used Bloom.

rol3d

Tobor said:

rol3d said:

Glow in render works great on the entire scene, however I just want one object to glow. I have a lightbulb; all I want is for the filament to glow, but with render-glow, the entire bulb glows.

Three ways, all of them fairly easy, though all three require combining images in Photoshop, GIMP, or other graphics program:

1. Render it twice, and in Photoshop, apply a layer mask to the bloomed image. Isolate just the lamp on this layer.

2. Click off everything in the Scene tab except your lamp, and render it separately with the bloom as high as you want.

3. Use the canvas feature, and select the lamp as a node. Render just the node. Be sure to half the Alpha option turned on. The benefit of this approach is that the shadow and ocluding effects of other objects are preserved. In other words, if your character is holding the bulb with his hand, the part of the bulb blocked by fingers will be transparent (won't render). This makes compositing much easier. Do a Google search here for rendering nodes on Iray canvases.

Thanks for your response but I would like to learn to do this without post work. I did try the following: made the filament a separate object – previously it was only a material zone of the entire bulb. I applied a glow texture to that: no improvement. So then, I created a 'Geometry Shell' of the filament and applied a glow texture, also changed opacity of the shell,  hoping the original filament would shine through … still no good.

rol3d

Fishtales said:

 

 

r reading your post I decided to do a render with a set I was rendering at the time. I used the method I outlined in my post above. It still needs a bit more work and this is only 50% done but I thought I would post it here for you to see.

Click on image for full size.

OK, thanks, looks good, I'm going to experiement with your suggestion.

 

rol3d

Connatic said:

I like doing magic and energetic effects.  All glows are in-render and I used Bloom.

Thanks. Are you using the same steps as Fishtales above?

rol3d

Here're the rults using bloom (again, only partial renders: these take forever)

Pic 1: no bloom, just a 'glow' texture

Pic 2: bloom turned 'on', threshold 10,000

Pic 3: same as Pic 2, but now also with Bloom Radius set to 0.1

Connatic

rol3d said:

Connatic said:

I like doing magic and energetic effects.  All glows are in-render and I used Bloom.

Thanks. Are you using the same steps as Fishtales above?

No, mine was done in one render, no retouch or compositing.

Fishtales

Connatic said:

rol3d said:

Connatic said:

I like doing magic and energetic effects.  All glows are in-render and I used Bloom.

Thanks. Are you using the same steps as Fishtales above?

No, mine was done in one render, no retouch or compositing.

Mine is in render too, no post work.

Fishtales

These should be the relative settings I used in the render.

Tobor

rol3d said:

Thanks for your response but I would like to learn to do this without post work. I did try the following: made the filament a separate object – previously it was only a material zone of the entire bulb. I applied a glow texture to that: no improvement. So then, I created a 'Geometry Shell' of the filament and applied a glow texture, also changed opacity of the shell,  hoping the original filament would shine through … still no good.

There are several Iray-specific issues here. The first is that in its current implementation, bloom cannot be applied on a per-object or surface basis. If you add too little bloom, you won't get the glow effect; if you add too much, everything takes on a "smeary" look. Sometimes that look is acceptable, and sometimes it's not. This is why post work often provides exactly what you want, because you're not settling for something in the middle. There is nothing wrong or bad about doing things in post -- compositing is a common practice in all 3D work, including animated features. 

Since you're looking to just making the filament glow, and not the whole bulb, you need to be careful how you shade the glass of the bulb -- or if you comp images, simply remove the bulb and render the filament only. Shaders on the glass can diminish the effect of emissive surface. Do a google in-site: search to the forum leads on how to apply the best glass shaders for self-lit bulbs.

rol3d

Thanks for all the great feedback! Gives me plenty to work with. 

BTW, I'm not neccessarily adverse to post-work, I'm a 15yr Photoshop 'veteran' - I need to be as I'm a live-music-photographer as a hobby. But as we all know, in film, the term '... just fix it in post' is not a much heralded one :) ... be it PS or AE. I am also trying to learn this thing, it as well is a hobby but the more I know of it, the more control I know I'll have.

 

 

 

mjc1016

rol3d said:

Thanks for all the great feedback! Gives me plenty to work with. 

BTW, I'm not neccessarily adverse to post-work, I'm a 15yr Photoshop 'veteran' - I need to be as I'm a live-music-photographer as a hobby. But as we all know, in film, the term '... just fix it in post' is not a much heralded one :) ... be it PS or AE. I am also trying to learn this thing, it as well is a hobby but the more I know of it, the more control I know I'll have.

There's a huge difference between 'fix it in post'...and it is easier/cheaper to do in post.

Trying to postwork out blatant problems and just bad work is not the best way to go about things.  Adding an effect that would be impossible/take too long/blow the budget...that's what the whole process is for. 

Connatic

I am not against using postwork.  It happens that the render I posted used only in-render effects.  Usually using bloom it does have some extra unwanted fogginess.  To fix that, I do a second version of the render with no bloom, composite the two images and use eraser to blend together what I want to show.  Soon I must learn the canvases layering system within Iray.

Tobor

What Mjc said. 

Iray was designed from the ground up for compositing. That's why they have the canvas, matte objects, light path expressions, and other features. nVidia anticipated you'd be using the renderer for compositing, which is why they took the time to add these features. They aren't fixes for something that's broken, but additional functionality that extends the capabilities of the renderer.

"Just fix it in post" may have had some negative connotations, but there's hardly an animated or visuals-driven film these days where a majority of scenes are not processed in post. Audiences have come to expect and demand the something extra that compositing can provide.

In the end, what you're trying to do with the glow from a specific is create a diffusion in front of that object. The diffusion creates a scattering and absorption volume that causes glow. For Iray, this means building some geometry in front of the object, applying a volumetric shader, and then hoping you get something that looks even basically passable. Because of the limitations doing this, they instead have the bloom filter, which is actually the "quick fix in post" -- the effect is added as a post process. You just don't realize it because it appears in the output window with everything else. Currently there is no way to define just a small area for the bloom filter, hence the other work-arounds. But make no mistake, bloom is a "let's fix it in post" solution, just like doing it in Photoshop

mjc1016

Tobor said:

 

"Just fix it in post" may have had some negative connotations, but there's hardly an animated or visuals-driven film these days where a majority of scenes are not processed in post. Audiences have come to expect and demand the something extra that compositing can provide.

I don't know of ANY film that isn't at least run through color grading/exposure adjustments.

rol3d

Thanks for all the additional input, I hadn't checked here for a while.

I think we're all fully aware that much post processing takes place in just about any visual/audio media -  I post-process extensively when composting music videos for example - there's no way to get some of the lighting and ‘texture’ effects of which I am fond with real light. So I wasn’t arguing against post-work as a blanket statement. But I do want to learn ‘this thing’ as much as possible, there will be plenty of post-work left I’m sure.

When I get back to playing with the bulb, I’m going to try as suggested and build some geometry around the filament and apply a volumetric shader; this would allow me to animate the camera (for example rotate around the bulb) and yield continuous, believable glow I assume.

I just need to find come time to play.