Struggling with Corona (and Special Buffers)

[MStrickland]

Cool Glows!!

I learned in the mailing list from Robert Wilson (seconded by Larry Schultz) that you can use Corona with Special Buffers to get some really cool glow effects.

(I was a SuperGlow2 user through 6.5/OS9 until Pontari stopped supporting the Mac for lack of interest.) :(

Anyway, I can't make it work the way I'm told it should in OS X, and since I'm getting INCONSISTENT RESULTS, I think that either Corona may be buggy, or the Special Buffers path may be buggy. I suspect Corona, but who knows?

Robert says you can create glows that just glow on the outside of objects, without that terrible additive "blown-out" surface look that Corona can deliver. And using Special Buffers, you can have as many as 4 different glow set-ups (different effects, colors, gradients, etc.), on up to 4 separate objects. All this sounded great to me, but after several hours of banging my head against it, I just can't seem to make it work.

So here's my request from the group:

1. If anyone wants to try this with me (especially if you also have a PC version of LW!, but even if you don't), I'll fill you in on how I have things set up, and maybe even email you objects, scenes, etc.

2. Has anyone else had inconsistent results with Corona (are there any known bugs with it?)

3. Are there any known bugs with Special Buffer on LW7.5c OS X 10.2.6?

Thanks a heap,
Michael

[toby]

I'll have a go!

Sounds like fun, I love problem solving/rendering/special effects, and I've used Corona many times including textures, threshold masks and input channels, and I'd like to learn about Special Buffers.

[Triple G]

I'd be interested in taking a stab at it. I usually do most of my glows and such in post, though I have used Corona and it's little brother, Bloom, from time to time. I'm running OSX 10.2.4 with 7.5c, if that makes any difference to you. :)

[MStrickland]

OK, here goes:

Make four simple objects (like a ball, a box, a cone, and a capsule). Give them surfaces called "One," "Two," "Three," and "Four." (How creative, no?)

Load them into Layout, and open the Surface Editor. On the Advanced Panel, select Special Buffers for "One." Set the first Special Buffer to 1.0, and the other three at 0. Now select texture "Two," and open its Special Buffer: set Special Buffer 2 to 1.0, and the other three to 0. And so on, for all four objects/surfaces.

Save the objects, save the scene.

Now in Layout, go to Scene:Image Process and Add Image Filter:Corona 4 times. (Apparently, these 4 iterations of the Corona Filter automatically correspond to Special Buffers 1 through 4, in order, and any objects/surfaces higher than 4 will always use the fourth Corona setting. -- I may not be completely clear on objects higher than 4.)

For now, uncheck Corona's 2-4. Open the first Corona, and Set its Input Channel to Inverse Geometry, and set its Threshold Mask to Special Buffer. For now, keep the Effect to Normal, the Falloff to Smooth. Set the Input Threshold to 75%, to make sure the filter has something to work with. Set the Strength to 200%, and the Size to something below 50, just for the sake of speed. Hit F9.

You should get some kind of "glow" around object One, and ONLY around object one. Now turn on the other three Corona's, and set them to something similar to the first one. Hit F9, and they should each display their particular effect, each being identified by the "Special Buffer."

Once you get to this place, let me know, and we'll talk about the "Edit Texture" button, and how it fits into this attempt at a "SuperGlow"-like glow. (I haven't reached the part that seems to work inconsistently for me, yet.)

Let me know if anything I've written isn't clear. (I tried to include a jpeg here, but I'm not sure if it was accepted.)

Best,
Michael

[MStrickland]

My Object and Scene files are here:

http://www.StricklandDesign.com/CoronaTest.zip

[MStrickland]

To restate one of the problems with using Corona to generate glows:

If you want a really HOT glow around the edge of the objects, without BLOWING-OUT the interior parts of the surface area, there needs to be a way to have the Glow appear ONLY OUTSIDE the edge of the glowing object.

That would be like SuperGlow2. But I haven't been able to find the magic combination of settings to make it work . . . yet. (And Robert Wilson says it's possible.)

And I think there may be a Corona bug in the OS X version, since sometimes I get the texture to appear, and sometimes NOT! :-(

MS

[Triple G]

Ok, this is what I have so far (this is with all 4 Coronas applied and active). Does this look about right?

http://home.comcast.net/~greggd/temp/corona_test01.jpg

I deviated slightly from your instructions, and set up the settings for one Corona filter, then copy/pasted it three times. I did a test render after each, and the glow for each object turned on in succession, so I assume this is ok? Also, I put all objects on separate layers within one .lwo, I'm assuming this shouldn't make a difference, but thought I'd mention it just incase.

[MStrickland]

Yes, Gregg, I also put all four objects in the same object on four layers (I'm pretty sure there is little difference between that and making four totally separate objects, except it's easier to manage the way we've done it.)

Apparently, all the Special Buffers do is assign the number (up to 4) so the Image Filter (Corona) can tell which one it's supposed to do its thing on. Simple, really.

Now my real problem:

(Have you ever used SuperGlow2 from Pontari.com? -- It's a very handy plugin from 6.5-and-earlir days, for making glows -- but not available for 7>, or for OS X) What it could do is what I'm after. As you can see in your render and mine, Corona "blows out" the actual surfaces that it is applied to. What I want to do (and Robert Wilson says it's possible, if I understood him correctly) is to have the Corona-glow extend outside of the object, but not ON the surface itself, because that makes the surface texture too bright, and blows out the values.

So . . .

In the Corona panel, there is an "Edit Texture" button. Click that and up comes the good ol' Surface Editor. Choose Gradient type, and give the key a color different that Object One, say.

Set the Input Parameter to "LW_CVorona Input Channel." Hit F9.

Take a look at my attachment; the first image is with no Corona, and the second one is WITH Corona. See how the glow is almost acting like a ring around the edge of the object (this is because of using "Inverse Geometry" as Corona's Input Channel), but is really changing/lightening the surface of the object as well. I don't know if it's possible to do this in LW (it may need to be done in post), but I'd like to figure out how to make the glow ONLY appear outside the edges of the object.

I'll post another message, with the results of another idea using the texture gradient . . .

Michael

[MStrickland]

In this attempt, I thought that I could maybe use the Gradient to "alpha-out" the inner (unwanted) part of the Corona effect. See the attachment.

I don't understand. This is what makes me think that maybe there's something "not quite right" with Corona/OS X.

What do you think? Shouldn't the Gradient show up in the render, instead of just the color of the LAST KEY???

:mad:

Michael

[MStrickland]

OOPS! Forgot the jpeg.

[toby]

I think it depends on what the beginning and end of the gradient ( special buffer ) actually are. It's not neccessarily the distance to the center -

I'm working on a scene too, just nothing to show yet

[toby]

Are you sure you're supposed to be able to entirely eliminate the glow from the surface of the object? In your first image you've shown that it doesn't blow out the color.

It seems like you're asking Corona to mask out the only thing that it can make the glow with. Maybe your other program just slapped the alpha onto the glow before adding it to the rgb?

[MStrickland]

Originally posted by toby
Are you sure you're supposed to be able to entirely eliminate the glow from the surface of the object? In your first image you've shown that it doesn't blow out the color.

It seems like you're asking Corona to mask out the only thing that it can make the glow with. Maybe your other program just slapped the alpha onto the glow before adding it to the rgb?

Toby -- My first image really does blow out the color. Just take a look at the subsequent image without any glow at all, and you can see quite a difference. The point is, if you could make an edge-only glow, making a separate inner glow would be a piece-o-cake, and it would be very easy to combine the two, to get it dialed in.

Yes, I am asking Corona to mask out the only thing it has to make the glow with, and you're also probably right, SuperGlow2 probably did slap the Alpha on there first, before applying the glow to the image. But I've been told it can be done in LW using Corona. Maybe not. -- ??

Your sample is exactly what I'm trying to do. Please tell how you did it? in Photoshop, AE, etc.? Or does it just LOOK like the surface isn't getting blown out?

If you did it in LW, did you do it on an Intel machine? or in OS X?

Thanks,
Michael

[Triple G]

Nothing new to report here. I tried fiddling with alpha gradients, and using different Input Parameters/Threshold Masks....I keep getting images with identical looks as what you've shown...in short, I've been able to figure out nothing which will give the look you're going for, Michael.

The only obvious solution I can think of is to comp it in post, which would save a heckuva lot in render time. Add to that the tweakability factor, and for most scenes, there's really no good reason to do this all in LW. I've never used the plug you mentioned, but I'm betting with Toby that it probably somehow applied the object alpha to the resulting image.

Though it does seem strange that other (Intel) users are able to do this, seemingly without a problem, without the use of any external plugins. Kinda makes me wonder, too, if there's something that's not quite right with Corona on OS X. :confused:

[toby]

uuhhhh, I totally cheated on that one...:D

First rendered the glowing object then rendered again without glow, used 'image controls' in the Image viewer to blend them by the alpha ( I set the floors' alpha to 0) then did a screenshot. ( I can't find a way to save a combined image out of LW.)

Certainly could be done in Pshop or AE

The second image could have been rendered with a different color glow giving you the effect you mentioned

"My first image really does blow out the color"

I guess what I meant was that you can make only the edges glow - you have more control, and you might be able to stop it from blowing out the center - I thought that might be what Robert and Larry Schultz meant

[MStrickland]

Originally posted by toby
I guess what I meant was that you can make only the edges glow - you have more control, and you might be able to stop it from blowing out the center - I thought that might be what Robert and Larry Schultz meant

It's this kind of talking that's tripping me up. :-)

You mean in programs OTHER then LW, (PS, AE, etc.) right?

Thanks,
MS

P.S. THANKS TO GREGG and TOBY!!
-- now all i need to do is get someone using intel to help me find out if there's a buggy-boo in corona/OS X

but first . . . zzzzzzzzzzzzzzzzzzzzzzzzzzzz