Expression for 3d area change

Scripting for After Effects

Expression for 3d area change

Postby Ze_Minderico on 09/29/2015, 5:32 am

Hi guys,

I´m trying to find a way to see how a triangular form change its area when moving.

My goal is to start with 100% area and see how it increases or decreases its size during animation. I need this to be in 3d, so my idea is to create a triangular mesh in 3ds Max and then export it to AE so i can calculate its area´s movement.

The model is the one in the photo..

Can you guys help me out?

Thanks in advanced!!
Attachments
triang_ANTROPsmall.jpg
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Re: Expression for 3d area change

Postby star+circle on 09/30/2015, 7:07 am

I don't understand what it is that you need help with:

What specifically are you having trouble with?

100% area of what?

Moving in which way? The camera? The object? Individual points?

Have you already created the 3D object in 3ds max?

Have you imported it into After Effects and if so, are you using Element 3D to bring it in?

What does the image of the face have to do with this?

Are you trying to move individual points of this face in 3D space in After Effects to create expressions on the face?

What are you trying to calculate? The size of the surface area of the triangle or triangles?

Or, more basically: Why do you want to bring it in After Effects rather than doing this in 3ds Max altogether?
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Re: Expression for 3d area change

Postby Farmfield on 09/30/2015, 4:25 pm

Ze_Minderico wrote:Hi guys,

I´m trying to find a way to see how a triangular form change its area when moving.

My goal is to start with 100% area and see how it increases or decreases its size during animation. I need this to be in 3d, so my idea is to create a triangular mesh in 3ds Max and then export it to AE so i can calculate its area´s movement.

The model is the one in the photo..

Can you guys help me out?

Thanks in advanced!!

It's called object tracking and is a variant of 3D camera tracking. You could try masking your models face while he moves and try to track that with the AE tracker, but you would likely have way better results using something like Blender (with it's build in camera- and object tracking system) or PFTrack which I have personal experience from tracking objects, it even tracks mesh deformations, it's crazy cool - but seriously expensive.
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Re: Expression for 3d area change

Postby Mylenium on 10/4/2015, 12:30 am

Ze_Minderico wrote:Hi guys,

I need this to be in 3d, so my idea is to create a triangular mesh in 3ds Max and then export it to AE so i can calculate its area´s movement.


AE doesn't natively handle any geometry and any means available in AE to import 3D objects don't offer low-level access to mesh components in the required manner and/or require the same level of extra programming as you would in MAX using Python or MAXScript. Your idea makes totally no sense.

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Re: Expression for 3d area change

Postby Ze_Minderico on 10/4/2015, 4:45 am

Hi guys,

Let me try to explain my problem!

I wanna do a study on how the triangles of a mesh change its area (based on the movement of certain points tracked from a face expression footage (like smiling)).

First i´ll do this:

- Film the model simultaneously with 2 cameras, making several expressions. The model will have several marks on his face to enable tracking. This is a must because i need to study the model in a frontal and side view.
- Divide the footage to individual expressions clips. (Anger, smile, pain, disgust,...)

Now my problem is this:

- In the end i need do have a clip that shows me how the triangles of the mesh change their size in order to know how areas of the face changes in different facial expressions.
- I am thinking of doing a graduated colour scale , so that it the "rest position" all triangles are grey, when one triangle gets bigger it goes to red and when it gets smaller it will go to blue.
I can do the animation in 3ds max and import it to AE. then i was thinking in apllying a COLORSLIDERtoSCALE effect to get the color to change when altering the scale.

MY PROBLEM is that i can´t make it to every individual triangle because AE doesn´t read the triangles MATERIAL´ID when i use ID MATTE. this way maybe i could duplicate the footage to the numbers of material id´s and aply the ID MATTE effect COLORSLIDERtoSCALE.

Is it because i´m exporting in .RLA or in .RPF the footage from 3ds max??

i hope i was able to explain my problem!
Thanks, guys!!
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Re: Expression for 3d area change

Postby Guitarboy2828 on 10/4/2015, 5:21 am

Maybe I'm still not fully understanding what you'd like to do. But from what I can gather, Plexus will do exactly what you want, all in After Effects. You can use lights/nulls as trackers and then it'll create the triangles. You can even colour them within Plexus to change colour as you explained.
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Re: Expression for 3d area change

Postby Ze_Minderico on 10/4/2015, 6:31 am

:D Thanks GuitarBoy2828,

i´ll try that!!
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Re: Expression for 3d area change

Postby Ze_Minderico on 10/5/2015, 2:58 am

Hi Guitarboy2828,

Plexus is really an exciting plug-in, but i don´t know why i can´t import obj sequences or object from 3ds max. I´m doing someting wrong for sure.

I´ve made the render size of the obj sequence the same size as the AE comp. I´ve located the object to export in the 0 position (x,y and z). I´ve tried to export in quads and triangles, i even exported just the obj file with no sequence and even that didn´t work.

Can you help me with this? Must i try with Cinema 4d ? I´m using 3ds max 2015 and i just can´t get it done!

Thanks!!
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Re: Expression for 3d area change

Postby Guitarboy2828 on 10/5/2015, 5:36 am

I've never used 3ds max unfortunately. I do know that if I export a model as an OBJ from Cinema 4d, plexus handles it really well.

Possibly this video will help you: https://vimeo.com/49138935

Maybe post the obj file here? I will give it a go and see if I can get it to work.
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Re: Expression for 3d area change

Postby star+circle on 10/5/2015, 11:33 am

Ok, I now at least understand what you're trying to do. I can only think of very complex approaches to this.

Unfortunately I'm not familiar enough with 3dsMax to know what 3D information you can export from there that AE will be able to read as individual animated points. Can you attach (animated) 3D lights to each of these track points and export them for AE? Or can you export those positions as (animated) 3D nulls?

If you can, I'm afraid it will still be a very complex affair to recreate the face with changing (facial) expressions in AE. TrackerViz, which I've never used, can apparently create mask path based on layer positions (such as nulls). So theoretically, you could recreate the triangles with it -- one by one. (It may be that you will need to convert the 3D positions to 2D camera positions.)

Then there is the matter of calculating the area of each of the triangles through time and comparing them to the original area to change the fill color -- well, if you can get this far, that is going to be a smaller problem.
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Re: Expression for 3d area change

Postby Farmfield on 10/5/2015, 2:47 pm

I really didn't get what you were after the first time I replied here, but from what I read now, if you want the angles/vectors behind the tracking calculated so you can use it for coloring or just write it out, this would be really simple to setup in Houdini, you could just calculate it in VOPs and export it as a parameter and then use that parameter for whatever you'd want to do. I'm guessing this would be as simple to do with MCG if you got access to Mac 2016 - or, if you're a crazy person, you could probably do the same using Thinkbox Genome or even set it up in Pflow with Box#3...
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Re: Expression for 3d area change

Postby Ze_Minderico on 10/8/2015, 2:54 am

Hi, guys,

I´m really enjoying te PLEXUS effect as it can read null objects attached to the track points. The thing is that i have to track something like 20 points in 3 clips which it can be done in a day´s time.

I´ll be filming the model in three views simultaneously (front, profile and 3/4), them track the points on his face for the 3 clips (points are previously drawn , of course). After that attach the null objects to the track points, aplly to a new solid the Plexus effect and.... i´m thinking of apllying a slider connected to the scale of the triangles with expressions.

Do you think this can work ??
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Re: Expression for 3d area change

Postby star+circle on 10/8/2015, 3:54 am

The general approach seems sound.

I would imagine you will create new 3D nulls for Plexus that derive their 3D positions from the three sets of tracked points.

I haven't used Plexus, so I can't say if it can connect specific dots the way you want or whether it does it automatically. Someone familiar with that program can tell you, or since you have the program you may already know the answer.

I would calculate the actual area of the triangle for coloring purposes. See:

http://math.stackexchange.com/questions ... d-triangle
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