lets talk about passes

hi,
i think this is the right place to post questions about passes

well, im trying to pass from a basic multy pass render guy to an advanced one. Can you help me? I have a LOT OF QUESTIONS about that.

why most render elements does not use antialiasing?. I cant find the good way to use a zDepth if it is pixelated. I've tryed with max default render elements and with vray too. I've tryed puting them in separated files and using .rla and .exr files too.

is the AA necesary or im just missing the god way to use that passes in composition?

render elements and passes, is there any difference or just two ways to name the same thing?

what is the beauty pass? why its particular name?

which is the difference between the raw and non raw passes?, examplo: raw GI an GI passes.

where can i find a table of render elements and composing blending modes?

thanks a lot in advance!

1) Anti-aliased z-depth will cause halo-like errors when you apply your post filter. Thus, 90% of the time you'll want to use an aliased zdpeth pass (all other passes should be anti aliased though). If you want an anti-aliased zdepth pass, apply a falloff material to all objects in your scene (where the falloff is determined by camera distance) and then render normally.

2) AA is necessary for ALL other passes except zdepth, unless the pass is going to be blurred or something (ie...a spec pass for the use post-glow)...although sometimes even an aliased spec pass (for the use of glows) will cause flickering...so to be safe it's usually a good idea to turn on AA

3) No difference, although rendering with some render elements turned on means the process will be streamlined. Ie, in max...with render elements turned on, you only have to render 1 frame for all the passes to be exported. If you don't turn on render elements, you'll have to render all passes manually.

4) Beauty pass is basically any kind of diffuse pass where textures are visible. It's called a beauty pass because it represents the beauty of the shot (ie....the main part of the shot that will be seen)...everything else is added ontop of this pass (ie, shadows, spec, glow etc) so this is the "base" pass

5) Never heard of this....although what it might be referring to is a "raw" pass where nothing is separated. Ie, a standard render where things like shadows, specular highlights, and different object layers are all present in one render frame, and not in separate passes.

6) In max, you'll find a list of all render elements under the "render elements" tab. In after effects, you can find a list of all blending modes under the blending mode selection list (in each layer's properties in the composition timeline).

thanks a lot for replying ivanisavich,

1) ok, i got it... then my problem is in the composing program... ill take a look to find what im doing wrong there!

2) Well, you make me realize im confused about render elements and "extra channels". How do you call a "material ID" render pass? This is the kind of thing im getting without AA. Maybe just like the zDepth it must be without it.

3) cool, thanks

4) great, i really had no idea about the meaning of beauty pass.

5) mm, im confused about that... i was looking at vray render elements examples few minutes ago.
http://www.spot3d.com/vray/help/150R1/e ... ements.htm

and what I think is raw images does not include the diffuse color information on it. Look at the "raw GI only" example and compare it to the "GI only" example. It seems like the diffuse data is the only difference. Maybe those passes are meant to be used in combination with the diffuse one to get individual control from each other.

now take a look at the:

"Raw lighting * diffuse (multiplied); the result is the same as the Direct Lighting only channel" (the last one from the first column)

the same thing happens between the raw lighting and the lighting passes.
Maybe im talking about carrots and apples but maybe im not fully wrong.


6) i was asking about how should i blend each pass.
which render elmente uses which blend mode to get the full RGB render but in passes. Im sorry about my english, i know it sucks!


new questions:

7) which is your favorite way to go from max to after with passes? RLA, EXR, separated files?

8 ) vray raw image file (.vrimg)
is that file format usefull in any way? does any vray user use it?

9) i think im going wrong using the alpha channel from the file format it self. I mean, maybe my problem is to use zDepth pass in combination of transparents png files. What do you prefer? alpha channel from the file format or separeted alpha element?

10) how can I animate a zDepth to get a change in focus during an animation? do I have to animate something at max? or at composing time in after?

one again
tahnks

Really interesting discution...I often had the halo-like problem with deep of field based on a AA zdepth pass...happy to know the solution now

now from what i know for cbaristo

=> 7) I think that's depends of what you need...Rla/rpf sometimes usefull for exporting camera moves in your compositing programs, or if you don't have a lot of pass and don't wanna play with tons of files. But for heavy compositing works, i prefer have seperate images sequences

=> sorry, i really don't know vray

=>9) once again, depends of the work...and of the scenes. A separeted alpha can be usefull for doing some mask/matte. zdepth, id, velociy, and all the effect-based pass often don't need their proper alpha or good quality...I usually render them in .jpg to free memory in my compositing program (it a lot faster for manipulate the effects than a huge rla/rpf sequence). I only keep alpha (with tga, but i guess it's the same with png) for the important pass as the beauty pass, or an occlusion pass, etc.. If needed, i can use the alpha from theses pass for the others ones

=>10) If your zdepth pass is good and have enough grey variation(it's the only think you have to care in max), you can simply use the dof post-effect (in AE or an other soft) to simulate focus change by changing values... You can also make variation on the grey value of the zdepth (with animated levels for exemple) to have some slow focus variation with your post effect..Tricky but can produce some interesting results

cbaristo,

I've been trying to figure out the compositing workflow using vray render passes myself.

As far as I can tell, the raw passes do not contain any diffuse color information, just illumination. So for instance if you want to turn up the sunlight in your shot you would crank up the raw lighting/raw GI in your comp.

IMO the vray raw image files (meta-data files like rpf, rla etc.) are pretty useless and usually get converted to .exr. Vray comes with a tool called "vrimg2exr" that does the job for you or even easier just change the .vrimg extension in your render dialog to .exr and hit render.

I usually render one multipass .exr for each frame. Some people don't like it because you can easily end up with a 10MB file per frame, but that way you dont have to deal with 10 or more seperate render layers. For compositing I use Nuke which works well with vray and lets me access all my passes contained in that .exr. You can use any other like Fusion or Shake.

check out the chaosforum...They have examples on how to comp this stuf

hi guys,
thanks for your tips,

andyburm, vray raw passes seams to be pretty usefulll then... what passes do you use?
LOL, i will try changing .vrimg to .exr extension, i didnt know that too, thnx, great tip.

i dont know nuke, neither fusion or shake, im after user. As far as i know i need extra plugins to get some channels like the velocity one.

cya!

you got to remember that with every pass you store your .exr (or whatever output you use) will increase in size which may not be a big deal for a still render but will definitely slow down your workflow if you're rendering an animation sequence. Again, the lighting/GI passes will give flexibility in case you want to do some relighting in post, however, i found it unnessesary to render lighting, gi, raw lighting etc.etc. as I try to get my renders as close as possible to the desired result that i need. Instead, I usually render color mattes for all my different 3d elements to be able to tweak those individually in the composite.

So, as far as passes i usually render:

rbg
reflection
refraction (if there is any)
shadows
specular
velocity
z-depth
[mattes] --> vray 1.5 has a pass called"multimatteelement" which is basically an rbg matte. You can set different g-buffer numbers for different objects in your scene and thus get a different color mattes generated.

To be able to use velocity passes in AE you probably have to use something like RE:ReelSmart MotionBlur.
http://www.revisionfx.com/support/faqs/ ... n_vectors/

You can render out your motionvectors with vray or with a script available on scriptspot (http://www.scriptspot.com/3ds-max/veloc ... nel-output) as I am not sure if the standard scanline velocity pass will work. Remember that a post 2d mblur is a quick work-around but will always give you artifacts and never look completely accurate.

Check out this site: It shows a simple comp using vray passes with different apps (incl. AE)
http://ignjat.web1000.com/tutorial.html

I could be very wrong about this, but I'm pretty sure the standard Max velocity channel pass works great, and CC Vector Blur ships with After Effects. Doesn't it work just like the Re:Flex one?

I tested the scanline velocity pass which does indeed produce usuable motion vectors, however, cc mblur doesn't seem to be able to tranlate these correctly. The moving object not only blurs without taking directional blur into consideration but also obscures the background immensely.

I am not the expert here but as far as After Effects, RSMB in the only plugin i know of that actually works with max velocity pass......

http://www.revisionfx.com/support/faqs/ ... %20Max%208

well, after a couple of hours and a couple of whisky glasses i made a scene to test what i learned here and to give a small tutorial to the forum.
Please tellme what you think and if you like another way to solve it. When i get more extra free time and extra jhonny walker i´ll give it a second try using different passes because a still having some questions about it. like, why specular pass is fully black? (i rendered it but did not use in this comp) and why should i render shadow pass... i know there is a lot of ways to render the same scene using passes and thats why i will continue bothering you guys, if you let me to, of course!!! : )

here is the scene i made, and the passes i rendered:


well, from particular to general i did this:

first I pre comp the diffuse channel just because if I want to add stuff to it later i will need to do it only one time.


then I made two more comps, one for lighting and one for GI

raw lighting multiplied by diffuse pre comp


raw GI multiplied by diffuse pre comp


then i mixed those two comps with reflection, refraction and caustics added on top in a final comp and I stencil luma the alpha channel on the very top layer.


here i got the same result as the RGB render but with alpha channel instead the white backgound.


then i precompose this comp again to add some post stuff like DOF with the zDepth pass, glow effect, noise and overall color correction as well as i color correct and manipulate the levels of GI separately.
I add a little of greenish fog too using the zDepth.

...and i got the final render.


well, comments are very welcome!!!!!
cya

dude, that looks pretty darn good

thanx man!!
i loved the control I got over final comp using render elements!!!! Thats great!!!

well, some auto crits...
- zDepth pass is kind of poor. I will re-render it to have a better gradient, dont you think so?
I needed to tweak it a little bit using levels to get some decent DOF effect.

- in the zDepth high contrast zones like the left sphere edge i got poor AA (take a look at final comp). Maybe this is just because the plugin i used (native cs3 lens blur). As you told me before aint the best option

cya!

nice cbaristo, good to see how ppl does it

one thing though, in the final composite, the caustics of the sphere is blueish, not green like the sphere it self

tnx man!!!
you are absolutly right about the caustics... fixed!

i remade the zDepth channel too, now i got a good one i guess... but it doesnt make a big difference once in postpro.
http://www.cbaristo.com/forums/simplycg/zdepth.jpg

the final look was updated in the same url
http://www.cbaristo.com/forums/simplycg/final_comp.jpg

now im playing with the multi matte element, just to see how it works.
this is the element result:
http://www.cbaristo.com/forums/simplycg ... lement.jpg

take a look at the edges, it does have AA but a terrible one i think. Is that ok?
here is a detail magnified by 2:



I used the Set Matte plugin to mask diffuse image using the blue channel from the matte element. Then i painted it red using default tint plugin.
But the edges of the matte does'nt look so good i think... what do you think im doing wrong?
here a screenshot:


take a look at the cone, you can see this irregular stroke all around the edge.
prety ugly, isnt it?

thanks in advance.

If you have "filtering" checked in the element settings it should have AA

Actually it is filtered, but the AA doest look so acurate. Weird!

what kind of AA filter are u using ? what are your render settings?

....."area" tends to blur and give artifacted edges.....try Catmull or Mitchell which both make for crisp edges.

well, I tried Catmull and Mitchell and matte element seems to be the same... ugly edges. what i noticed is that ugly edges appears between objects, but when there is alpha above an object the edge looks smooth. cheers!