PDA

View Full Version : Learning About Render Passes


NeptuneImaging
09-13-2005, 03:17 PM
Hey, I just started learning about render passes today (the ONLY thing I haven't really learned in XSI), and I must say it is so much easier than the manual makes it. However, it there a way to have the passes as its own properties? Such as I have the Shadow Passes rendering a shadow image, but when I want to render Highlights, there is still a shadow in the image, and I want to get rid of that with an override. I had to do it long hand, by selecting the highlight pass and turning off shadows....

in fact, do I even have to turn off shadows on anything....?

Thanks a bunch, I will post my learnings :)

jamination
09-13-2005, 04:58 PM
you can turn off the shadows for that pass in the render options under shadows. change regular to none.

NeptuneImaging
09-13-2005, 05:27 PM
Oh, okay, I got that part, but what if I want to just let all of the passes render at once....such as in a film environment....

Oh, and I saw that Strangehold trailer, that was so awesome

Felipe
09-13-2005, 05:49 PM
But you have render options for each pass independently. Open an explorer window and hit "p" for passes. You'll see a render options for each pass. If you want to change some option for all passes you can multi-select all of them and make the changes. Its very straight forward process.


Cheers,

Felipe

NeptuneImaging
09-13-2005, 06:02 PM
Thanks, Felipe :). I think I am going to enjoy doing passes...the only one I have not tried is GI...which seems to take a long time to render and it is very aggravating....

NeptuneImaging
09-13-2005, 09:57 PM
Does anyone have any images of what a GI pass image looks like?

young_927
09-13-2005, 10:31 PM
I have a question regarding with render passes also..
are you able to render more then one passes at once?
like ie.. shadow, diffuse, dirt?
I have been just rendering one pass at a time ... didn't know if there was an option where u can set up all the passes and just render all...

NeptuneImaging
09-13-2005, 10:58 PM
Yes, you can render all the passes at once, but I am playing it safe and doing it one at a time

Atyss
09-14-2005, 01:22 AM
I have a question regarding with render passes also..
are you able to render more then one passes at once?
like ie.. shadow, diffuse, dirt?
I have been just rendering one pass at a time ... didn't know if there was an option where u can set up all the passes and just render all...

You can render all passes at once with Render > Render All Passes, or you can render the selected passes with Render > Render Current Pass (I know, the name doesn't suggest such use).


Cheers
Bernard

Atyss
09-14-2005, 01:25 AM
Does anyone have any images of what a GI pass image looks like?

This is a somewhat subjective topic, as a GI pass is basically a pass where there is GI transports going on. It means that color transferred to bouncing photons change the photon's properties in terms of color and energy. All in all, to properly render a GI pass, you need to render at least diffuse, ambient and shadows. Rendering GI without final gathering may yield blotchy result that can be efficiently solved only with FG.


Cheers
Bernard

NeptuneImaging
09-14-2005, 02:08 AM
Hey Atyss, I am glad you replied, I was working on a scene, (I still am), and I wanted to render a GI pass (with FG combined). But when I created the pass, the render was mostly a blue hue that had the shapes of my objects but I did not bother rendering it (due to the constant shader on a dome), and it looked weird....

I did though composite my images and made it look like the XSI render. I think that is cool...but I am having problems identifying an GI/FG render pass image

NeptuneImaging
09-14-2005, 03:23 AM
here is my first Composited image done in photoshop, and the models were made in XSI....I choose simple models because they could be easy to study....and learn more about passes and compositing... I do realise the limits of faking Depth of Field, so I will use it sparingly

I will do my damndest to render a GI/FG pass....

http://i4.photobucket.com/albums/y122/JamesRayder2026/Composite-Practise.jpg

ThE_JacO
09-14-2005, 04:00 AM
one thing needs to be said...

I read a lot of people approaching passes like if they are a locked down thing and there's only a certain number of them you can have.

Passes, what passes you need and what they do, are NOT set in stone.

passes are just a convenient way to manage multiple outputs for shading and rendering configurations, but there's absolutely no point in trying to use a GI pass if you don't need one, nor it's possible to show a pic of "how a gi pass looks", for the very simple reason that it doesn't look the same in two frames.

a GI pass is in most cases the same of a diffuse pass, except that it uses GI to illuminate the scene.
other times a GI pass could be a pass of your scene in grayscale to replace the ambient occlusion pass, and other times again (but more seldomly) it could be a complex multiplicative or shifting pass to add colour bleeding to a diffuse pass.

get in the habit of considering passes for what they are, a convenient system to have multiple outputs from the same scene, they are NOT predefined configurations that are always used the same way, nor the same amount and kind of passes is always required.

sometimes all you'll have is a beauty and a couple mattes, some other times you'll have 30 beauty layers and another 50 mattes and overlays.

NeptuneImaging
09-14-2005, 04:36 AM
Ok, Jaco...that is a very good explanation for me. In my short film I wanted to use GI so badly, but I can fake it with Ambient Passes and have it controlled in photoshop...I see no problem with it... and I guess GI is awesome only in still shots...

Thank you Jaco and everyone else here.

BTW, how is my composite to you guys. I know it still needs work.... :)

ThE_JacO
09-14-2005, 05:44 AM
when you want people commenting on your comps also put thumbnails of the originating passes, otherwise we won't know what's comped and how.

as for how it looks... well it's a phong shaded revolved mesh infront of something with a linearly distributed blur, hard to make a call on the creative side of things :)

-wT-
09-14-2005, 06:00 AM
One thing I'd like to know from you experts, is how to get Photoshop to handle premultiplied-alphas properly?

As we can see on HaloAnimators image, the edges of the revolved foreground-object are quite horrible :)
I remember reading somewhere it's because of the alphas being premultiplied, although I remember turning premultiplication off in the render settings and Photoshop still doing horrible work when cutting objects off images with alphas...

Like for an example, in DFX+ which I got with LW, there's a simple tickbox in the image-loader node about alpha-premultiplication, turning it on instantly fixes those horrible Photoshop-edges we can see in HaloAnimators image.

NeptuneImaging
09-14-2005, 06:16 AM
Thank you wt. yeah, I had to set the anti-aliasing fairly low, and I had to lower the quality...any higher and I would have fallen asleep waiting, this was just a quick test to see what I can pull off, and I will post my precomp renders :)

The Jaco, Here are my pass renders. In my film, they will be higher quality and there will be no Depth of Field....

NeptuneImaging
09-14-2005, 06:18 AM
and here is the diffuse...the first image is the Depth pass, the second is highlight, and the third is the shadow pass. The jagginess seems to be caused by the depth alpha because I chose the wrong radius. I am using Photoshop CS and the Lens Blur

CGTalk Moderation
09-14-2005, 06:18 AM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.