What Render Pass to use for masking in AE in post?

[shauncarollo]

Hey guys. I'm working on my first animation for the architecture firm I work at. We're doing a photo real fly through of our new office in downtown Grand Rapids, MI. There is one part in the animation where the camera goes up through a cut in the ceiling tray, exposing all the concrete beams, and into the mechanical systems and then orbits around the building which will showcase our firms mechanical/electrical engineering etc. At this point in the animation, I only have the mechanical and electrical layers (systems) showing, but I'd like to further the separation of the two systems by being able to mask one in After Effects in post and make it glow red or white or something as we have text highlighting that.

 

Is this possible to do with render passes as masks, or is there an easier way? I haven't really got exposed to render elements yet as I'm new to the post production side of things.

 

Thanks!

[notamondayfan]

http://arddigital.co.uk/effect-id-changer/

 

Render your masks at the same time as you render the animation. Then in After Effects use the Shift Channel the extract only the part of the MMID you want and use it as a track matte in your comp.

 

Dean

[Corey Beaulieu]

You can render a MultiMatte and then use a Set Matte and simple Choker to get it to matte cleanly. You can pass on the Choker if it doesn't seem to need it, but you may want to anyway.

 

Otherwise are you can render a separate pass as an alpha matte where you don't need lights or GI (saves on render time)and then can just track matte it in AE, but this does require a second render.

[shauncarollo]

You can render a MultiMatte and then use a Set Matte and simple Choker to get it to matte cleanly. You can pass on the Choker if it doesn't seem to need it, but you may want to anyway.

 

Otherwise are you can render a separate pass as an alpha matte where you don't need lights or GI (saves on render time)and then can just track matte it in AE, but this does require a second render.

 

I think if you answer any more of my questions on this forum that I owe you a beer. Or a case. I swear you've had an answer to every question I've ever posted. THANK YOU!

[shauncarollo]

Ok, so what is my best workflow for obtaining a mask for the HVAC, and then a seperate layer mask for the electrical lines here? I already have RGB rendered out, so all I need is the masks--I just don't know how to do it most efficiently. Here is a pic of what it looks like about 25% around the path so you can get an idea of what I'm trying to do.

 

 

Thanks.

[John Dollus]

for rendering masks, you can turn off GI and just about everything in the global settings tab like lights, shadows, reflections etc. to make the process efficient. Just don't change the image sampler at all or the mask edges will not be the same. i usually just do the vray properties, matte, alpha -1 flags to knock out my mattes on a per object basis. You can also use the multi-mat render pass to get more than one matte at a time but old habits are hard to break sometimes so i still do it the old way

[shauncarollo]

Does this require a re-render of the entire scene? and if so, can I do one for the electrical lines, and a separate mask for the HVAC all in one pass? Or is it something that is done within a few seconds per frame? That way I just just do one for each. I guess the complicated part for me is just setting up everything so I can get one mask per group of objects, that takes into account that one set of objects is in front of the other in the scene.

[John Dollus]

all you are interested in is the matte, so it renders super fast. check out the help files on the vray render passes. there are a few ways to handle that and it may take some experimentation to find what works best for you

[Francisco Penaloza]

Before you render anything, you have several options to create mask, by material, by object, by wire color.

just plan a head and see what will be needed, in your case, you can select all you HVAC and put a object ID to them, or if they are using a unique material you can put a Material ID, or select all of them an assign one wire color, then on the render screen go to render element and you can choose, VRay material ID, VRay wirecolor, Mutlmatte, Object ID and so on, this way at the same time that you are rendering you are getting all the extra passes need for post work, reflection, refraction, shadows, mattes and more. You can render separated too as other people proposed but I usually do this when the objects are in complex situation that a simple material ID or Object ID can not isolate.

[shauncarollo]

The problem now is that I cannot get anything into my Alpha channel in two separate scenes. I can save the Alpha as a TIFF right? Are there any settings that need to be checked for this to work besides enable vray alpha in render elements?

[shauncarollo]

Ok. Since I can't seem to get any help, or maybe what I'm asking isn't possible...I will offer $20 paypal'd to anybody who can offer assistance with it to set up a quick render out of these alpha passes. I'm getting down to the wire and don't have time to try and fix this on my own as I'm already compositing the rest of the footage.

 

Ideally, I'd like to render one pass, no RGB, just with a mask for each set of systems. First one to message me on here gets it! But keep in mind, I've already messed something up with my alpha as I'm not getting anything but a black TIFF right now.

[Francisco Penaloza]

ha ha ha good offer

what you mean you can't save anything in to alpha?

By default when you save your image VRay will save a separate file with the alpha, now this alpha will only include your whole mesh isolated with the background, now if you are using a dome light and this still visible this alpha will not work.

Now the way that I explained is better because you render everything at once.

IF you have your animation done and you need to isulate any element, a simple way is, turn off your GI, apply a black material to everything and a white material to your element to isulate, this way you'll have a black and white image that you can use as mask.

 

Other solution is apply any material to everything with a VRayMtlWrapper then check the box Matte surface and change the Alpha contribution to -1 now if you save your image as Tiff, EXR, PNG, TGA will show only your hero object everything else will be alpha or non existent in your image.

[John Dollus]

It's not that nobody can help you. It's that there are so many ways to deal with it, it's difficult to tell you something step by step that is guaranteed to work for you. It's a bit of a downside to Vray IMO. It's extremely flexible to the point of confusion at times when you are getting started with it.

 

give this a go - it's old school but works every time and is pretty much foolproof:

 

1. save a duplicate file as -matte.max

2. in the display panel, hide by category lights and cameras

3. select all (ctrl-A)

4. right click with your mouse button and select 'vray properties' on the bottom

5. in the panel that comes up, click on the white box next to 'matte object' in the upper right

6. two spots below that, change 'alpha contribution' to -1

7. press 'close'

8. select your HVAC objects you want an alpha channel for

9. right click with your mouse button and select 'vray properties' on the bottom

10. change 'alpha contribution' to 1

11. press 'close'

 

what you have just done is tell vray to only render an alpha channel for the HVAC geometry.

 

12. turn off GI, and the following in the Global switches section: lights, hidden lights, shadows, reflection, glossy effects.

13. render to a Tif file but double check the 'setup' button in the file dialog box where you type in the name of the output file. Max tends to deactivate the 'store alpha channel' option.

14. render 1 frame and check the alpha before rendering the sequence you need.

 

#13 is super important

 

Hope that helps.

[notamondayfan]

http://www.scriptspot.com/3ds-max/scripts/quick-mask

 

$20 please

[Tommy L]

Ok. Since I can't seem to get any help, or maybe what I'm asking isn't possible...I will offer $20 paypal'd to anybody who can offer assistance with it to set up a quick render out of these alpha passes. I'm getting down to the wire and don't have time to try and fix this on my own as I'm already compositing the rest of the footage.

 

Ideally, I'd like to render one pass, no RGB, just with a mask for each set of systems. First one to message me on here gets it! But keep in mind, I've already messed something up with my alpha as I'm not getting anything but a black TIFF right now.

 

Shaun, your question was already answered, but it will require a little reading if its the first time youve done anything with VRay element passes and AE.

 

Here's some tips:

1: Dont use an alpha channel unless you are isolating one thing only. I typically just use an alpha to seperate the background. That means everything in your scene will respect the background and you can pull that from your beauty pass.

2: Use material ID to select things by material. This means your material ID pass will have all your ID's that are not set to 0 as unique colors on one pass. This can be an 8bit pass (jpg). Material reflection and refraction parameters should be set to diffuse only (not 'affect all passes' or whatever is says in the dropdown in the Mat Editor) or you'll be dealing with color ranges rather than a pure color in post.

3: Object id pass is useful for isolating objects that have multi-sub objects applied or for a bunch of objects. For example, if I have a car that passes in front of lamposts and I want to comp in people in between foreground elements I can isolate those via a Object id pass.

4: In AE you have a bunch of keying options. Keying is the lingo for isolating objects in post. Some tools are designed for greenscreen keing (e.g. Keylight) and deal with color ranges and in/out mattes, garbage mattes etc. The ones you want to focus on are flat color mattes, such as Color Key.

5: The more complex your scene in terms of how many separate adjustment controls you want, the more you'll have to think about how to isolate those objects/materials/effects in relation to one another. Chances are you'll need one MatID pass and one ObjectID pass. Both easy to set up, both easy to use.

6: Try this out on simple test objects to get the hang of the logic. Its simple when you know how...

 

Attached are some examples of passes for a scene I just got done with. Note that the main Z-Depth is a composite itself, I had to bring in the people clip-maps sequences and the tree pass and pre-composite those over the main scene files' Z pass. I also had to pre-motion blur that pass as its used after the movie is compiled, to MB the DOF-ed movie. Other than that the passes are all straightforward.

The trees had a mat ID pass so I could control the leaves seperately from the trunks. They had an object ID so I could mask stuff in front/behind them and were on an alpha for a clean comp over the footage.

[shauncarollo]

Thank you everyone for your advice. I finally had time to step away from the compositing and get back into Max and I figured it out. John, I will send you a PM regarding the Paypal, I couldn't get the alpha channel to show up until I followed your advice. To everyone else; thank you very much.