Hello,

I'm looking for a way to get an acces to the color of some model in a MultiLayered EXR (the problem is not to tint a light but only one specific model).
I must admit that I do not find any good way because I cannot get easily the silouhette of a model in a single layer (any way to re-find an alpha channel ?).
- if I increase the 'ambiance intensity' of the model, I get a layer with ALL the ambiance of the scene.
- I have tried many combinaisons of postEffetcs with no success, maybe am I in the wrong way ?

This is for professionnal work (I will have to make soon one full 3d animation for surgical techniques a week : AM Composite will be a wonderfull tool in the pipeline)

Many thanks for your help.

Alain

Just make all the objects you don't want in the alpha channel inactive and rerender. You can then use this alpha channel in photoshop to mask your tint on the orgional rendering. When I get a chance I plan to add the ability to swap alpha channels in A:M composite. That in combination with the existing "over" post effect would remove the photoshop step.

Thanks a lot Noel for your quick and precise replies !

To be honest, having to start a new render for each model (all other models beeing made inactive) of a unique choreography (1 choreography = 1 shot) is absolutely tedious and could lower the power of AM Composite.

We are about to plan to make a computer only working on renderings. Due to the complexity of the subject (surgical techniques) and the amount of work to do, when the Staging, Animation and First-Look Image Aspect will be set, the Rendering will be sarted ONCE AND FOR ALL to produce a MultiLayered EXR sequence (that will be further touch-up in AM Composite). In other words : 1 surgical technique shot = 1 choreography = 1 EXR sequence rendering.

So, do you mean that, without changing A LOT the programming code of AM Composite, it would be soon possible to just set in the renderer panel (or anywhere else) what 'shortcut to models' sould be or not rendered in a separated alpha channel (in theory, we just have the n silouhettes of the n models in n separeted layers) IN ADDITION to the current multi-layer set.

Congratulations for your efforts,

Best regards,

Alain

We are thinking of someday adding the ability to seperate groups of objects into different buffers but that is beyond the scope of the initial functionality of this feature. You will have to split your choreography into multiple choreographies/renderings and composite them together for now.

You can use the multiply, mix and the tint operators to merge two images using a third matte image.

[attachmentid=12999]

Yes, but the 'third matte image' comes from a separated new rendering.
I was look for a one unique rendering.

Thanks for your opinion,

best regards,

Alain

actually It's all from one rendering. I used the ambience channel and the diffuse channel to create different colour channels and the shadow channel as a matte. I use Skycast lights instead of ambient light, so the ambient channel is redundant in many of my images. This allows me to use the ambient channel as an additional render pipeline. in the case illustrated it allowed me to render two seperate texture versions of the same scene. But by assigning different ambience values to different objects it could also be used as a object identification channel. Using an exterior compositor you could take the seperate colours and create mattes for each object in the scene, although there would be some antialiasing on the edges of objects. Motion blur and transparency could also become issues, but motion blur could be handled in post if necessary.

(Problem 1)
I have re-done your idea for a default chroegraphy in wich I have dropped two different models.
I can set a different ambience colour for the two models.
But to get something in the Ambience Layer in the rendered .exr file, I must also set 'Ambience Intensity' for each of the two models. And making that also affects the Rendering (ColorAlpha Layer) !

What is the problem in my process ?

Thanks a lot.

Alain

I have another problem (problem 2)
If one model of the scene (model A) is partially between the camera and another model (model Be), and Model A is semi-transparent, there is no easy way I know to get the full shape of Model Be with a ColorKeyer.
Silouhette of Model Be is always partially gotten : no way to make an alpha channel for it...

Do you have an idea ?

Thanks

Alain

Not at my computer at the moment but if you are already using a compositor to adjust the different light buffers, you can throw away the ambience and recreate it from the other buffers. In many cases you could simply use make composite and delete the ambience step.
If you only need to key three colours you could set each objects ambience colour to a primary eg Red Green and Blue, then key off the indiviual ambience colour channels. This would require an external compositor, but from memory you use Digital Fusion don't you Alain?
John (still learning Composite)Artbox

Yes John,

About the 1st problem :
It can be solved by re-making the right RGB image with a Mix with the Ambience Layer :
- input 1 (RGB image) : + 100 %
- input 2 (Ambience image) : - 100 %

About the 2nd problem :
no solution I find (but I'm not a compositoir expert).

Any Idea ?

Alain

If you only have three objects to seperate and make each object have a pure primary ambient colour, the you can key your red green and blue channels seperately. even if a blue object is in front of a green object, keying on just the green channel should give you a decent key. For more objects one option it to use light lists that illuminate individual models. See attached EXR file example.
Set light buffers for individual lights and you'll get a set of buffers that provide you with key selections for each object.With a multipass render create the buffer lights with large sizes so they illuminate the objects in a relatively flat manner.
Because the lights do not cast shadows they add relatively little to the rendertime.
Here's an example EXR result [attachmentid=13090]

Thanks John,
Its fun to play around with these files.

For anyone experimenting don't forget to Right Click on the EXR image shortcut in the Project Workspace and select [Build Composite]. If you don't you won't be able to edit and see the composite elements.

I've been working on a walk through of Greg Rostami's demo to get everyone going with it but haven't got it finished yet. Not sure when it'll get done.

Very interested in this.
Rodney