Preserved Topic: Rendering in passes (Page 1 of 1)

Over the weekend, I played around with a technique called 'rendering in passes'. It's described in a book I purchased a few months ago calld "[Digital] Lighting and Rendering".

The key advantage to this technique is that you end up with various aspects of the render in seperate layers in Photoshop. This lets you alter an object's color, or reflectivity, or shadow intensity, or whatever in Photoshop rather than within the 3D application. Since a small adjustment and re-render in a high-quality renderer can take minutes or hours, the speed increase is tremendous.

This is especially valuable in the graphic arts industry, since you can very quickly make adjustments that a client requests, but it also acts as a 'creativity enabler', since you can very quickly and easily adjust your scene in Photoshop, until it's 'just so'.

I made a quick html doc, since the images would get edited into links anyway:

ballroom



[This message has been edited by Das (edited 05-02-2001).]

[This message has been edited by Das (edited 05-02-2001).]

This is something I've been thinking about lately as well. I'm going to need to tweak a lot of elements in my scenes and passes + Aftereffects seem to make the most sense.

There is a site called DV Garage ( www.dvgarage.com ) It's run by some pro's who worked at ILM and such studios, they make quicktime tutorials showing how they do things. So far it's mostly surfacing stuff, but there is a 2 part tutorial in there on render passes. It's quite indepth given the short quicktime movies they have, but it's very interesting to see.

-Electro www.badsun.com

OOOOOOOOOHHHHHH....What progs can you do that in...and how?

Rending in passes is DEFINATALLY a great way to save yourself from a headache. It has saved my butt many times.

I think thats one of the many reasons i tend to lean more towards XSI than maya. It makes render pass's so much easier, and even "previewable".

If only more colleges would teach students the values of compositing and rendering in pass's...i think we (as an inudstry) would benefit greatly from it..instead of having to take the time to explain the process to a newly graduated employee (i know my college didn't teach us).

--now inc

www.now-incorporated.com

Oh you mean this guy's book. Good, I've been wanting to purchase that book but wanted to ask someone what they though of it. So Das, what do you think of it??? Does it present the concepts in a pretty clear way?

-D


It never hurts to always be right.

I remember when this was brought up in the PS forum. Well, not the exact same thing, but pretty much. That was a hell of a break-down you gave, Das (that was you, wasn't it?).

I've used this technique for slightly different things.

Like Alpha channels for one.

Another use is rendering b&w with several light sources, one light at a time. Toss them into PS and start messing with Image > Apply Image. I read an article about doing this with photos (lost the link), but it can easy be used with rendering.

I've even used this for making D-Maps with funky shapes.

Rendering in passes is just plain useful for so many things.

Drakkor - excellent book. It teaches lighting better than any other I've read. I'm still fairly weak in lighting; it's considered by many to be the hardest thing to learn in 3D graphics.

warjournal - yeah, I used a similar technique to make some glass 'pills'. I'm kind of proud of that, actually. I came up with the technique myself, before I'd ever heard of it. Mine was more limited than what is presented in the book, but it was the same concept.

Found 'em.

Here is were I first heard of it: Raytracing in Photoshop. And there is a link to Synthetic Lighting on that first page.

Dude, love playing with stuff. So far I've just messed with lighting techniques menthioned in the links. Well, a few of my own variations of course.

I'm just starting to fiddle with other applications of this technique.

Bah! Set it up, render, change some things, render, change things around again, render, etc. I usually render more files than I'll need. Rather over-kill than under-kill.

And that's not to mention manipulating techniques once you get it all into PS.

Save save save. Practice practice practice. It does get easier and will save time down the road.

Hey, I just thought of something for using this for lighting. Be back later.


[This message has been edited by warjournal (edited 05-04-2001).]

Okay, it's later and not much of a revelation.

Let's just say that I find it easier to toss all of my lighting renders into one PSD. I'ld rather have one open file with a bunch of Layers instead of a bunch of open files with one Layer each to fiddle with.

No biggie.

I'm not sure I understand. How would you composite the passes if they weren't layers in one PSD?

The first step I do is pull all my passes into one Photoshop file, then I start messing with layer modes, layer masks, opacities, and levels/curves.

Image > Apply Image. As long as the dimensions are the same, you can pick another file for this operation. That's the driving force behind using multiple passes for lighting things. I'll work up some technical slop on this later.

In the mean time, Das, I would love to see one of your PSDs for your uses. Like I said, I'm just starting to explore other uses and I would love to pull apart some of your Layered work in this. If you dont' mind. Post, e-mail, whatever.

edit: sig be gone


[This message has been edited by warjournal (edited 05-04-2001).]

Ah! Never ever used Image->Apply Image, lol. Doesn't seem to offer enough post-compositing tweaking capability, but I can see a use for it in my technique. I currently copy/paste all the renders into different layers of one PSD. Copying all these images may be quicker with apply image than cut/paste, especially the channels. I'd still apply the image to new, empty layers, with blending mode Normal. This would still allow me to adjust the settings on the layers to tweak the compositing.

I'll post the PSD for this image in a bit. I'm on the wrong login to have FTP access atm.

Here's the PSD. Fair warning: it's 1.5MB

ballroom3.zip

[This message has been edited by Das (edited 05-04-2001).]

So...am I allowed to be told how to do this...or is it to lengthy to do here?

Skaarj, the idea behind this is rather simple. Imagine doing Doc's glass ball tut, but instead of using PS for the different Layers, they are rendered in your favorite 3D prog. Then tossed into PS and put together to taste. You know, blending modes and various Levels/Curves/HSV tweaks. Specular not good enough? Grab that Layer and give it a Gauss/Levels combo.

The part that really takes practice is execution. First part is doing the renders. Set it up for one pass, render, save. Set it up for another pass, render, save. Get as many as you think you'll need, perhaps more than you'll need.

Second part is putting it together in PS. Tweak ahoy! Don't like the Hue of that red ball? HSV is a snap. Shading giving you canipshit fits? Level or Curve that bad boy.

Does that make sense?

So far I've only played with lighting using Apply Image. Well, I did do a specular layer once because I was so pissed at the time. LOL! That was pretty funny. I finally said, "Fuck it." Then I blasted the whole scene, tossed in just specular, and worked with that. Man, I was just plain pissed at the time because I couldn't get the specular just right in the 3D prog. I was so mad at the time that I didn't even catch on to what I was doing. The implications/applications of the technique just blew right over my head.

I'm at a loss of inspiration for an example of how I use this (how I use this so far). When I upgraded, I didn't bother with archiving those files, so I have to build my base from scratch. Maybe a torus with a cheap texture and a bump. Hmm...

Anyways, thanks a bunch for the PSD, Das. Mucho gratious, amigo.

BTW, Das, don't cut yourself short when you did those layered pills thingies (limited my ass). Very few people would have thought of that on their own. You put those pieces together on your own accord, you just needed to explore it a bit is all. Shows the ability to think lateraly and to reverse-engineering your own backdoors. Know what I mean? Big time kudos for that.

edit: damn sig keeps sneaking into my posts. reminder to self: turn sig off next post.


[This message has been edited by warjournal (edited 05-05-2001).]

Dude! They use this in movies. I just remembered seeing an episode of "Movie Magic" where they went over how they animated Enterprise's fly-bys using multiple passes. The only pass I remember specifically is the deflector shield. Very cool.

I saw the same kind thing on The Mummy DVD where they showed how they did some of the effects. It was called compositing and they animated different portions of the final scene and composited them together. It was pretty sweet.

I think as far as image stills go, you should always go with a 2D prog and a 3D prog. I've been playing around with the technique Das was talking about and hopefully I'll have something to show you guys soon.

Compositing is actually a more general term.

The key aspect of this technique is that you render different 'parts' of the same object, such as the shape, the color, the reflection, etc into different layers. Then you composite the different aspects of the object together to make the final object. You might then composite the final object into a scene.

So you use compositing when you render in passes, but you also use compositing when you just want to put different objects into a scene

I've recently discovered that Max 4 will help out with this technique a lot. You can set (in the rendering dialog) different output files for what would normally be different passes, and you only have to render once. Max puts the diffuse in one image, the reflection in another image, etc. Very helpful. I just got LightWave yesterday, though, so I probably won't be using Max till I've played with LW for a while

I just looked up 3ds max 4 on their site. Looks like a damn handy feature.

I'm giving up on this for now. My patience is at it's end. I think I'm just trying to do too much to fast. Ahhh! I'll tell you this, 3d progs have changed quite a bit in the past years since I left the scene. Who knew?

edit: grumble sig

[This message has been edited by warjournal (edited 05-06-2001).]

Yes...I just downloaded to data sheets on 3DSMAX 4 in PDF format. Biggest problem in printing them for me is that Adobe Acrobat removes all the spaces between all of the words when it prints them...very annoying, plus there's no way that I know of with out buying Adobe Acrobat encoder to copy the text or extract the images. Grrrr...

Good stuff in this thread. For more info I'd check out the site electro mentioned, http://www.dvgarage.com/, and look in their weekly lessons for the two-parter on rendering in passes, explains these things REALLY well, great stuff...

Chris

KAIROSinteractive

So...do you actually know which ones it is do you?

Ok, we'll take thsi slowly. Register, go into the weekly lessons, and look for the two-parter on rendering in passes It's the ones from the weeks of 3/01 and 3/09...

Chris

KAIROSinteractive

HA fucking HA!!!!Thank you SMARTASS!! I'd already done that, but didn't know which weeks it was.



[This message has been edited by Skaarjj (edited 05-12-2001).]