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pekka varis
02-05-2018, 12:22 AM
Hello!

I am doing a spot movie with a dancer girl in the middle and large balls spinning around her. Here is a draft render of balls:

http://www.catchline.fi/toveri/loikka-temp5_000.mp4

Now my problem is that when I put a luma keyed ( masked with alpha ) girl in the middle of the screen with AE - the all the balls are spinning behind her. How can I have parts of the balls + particles rendered just in front of her so I can then put this layer on AE above the girl ?

I do not want to delete any balls and I do not want to animate opacity of each ball every time they spin around. I want to have a quick solution. In blender I have used "mask object". Does lightwave have such a thing? See this and you understand better what I am looking for:

139932

Yours,
Pekka

Sensei
02-05-2018, 12:52 AM
How can I have parts of the balls + particles rendered just in front of her so I can then put this layer on AE above the girl ?

Balls have Z-depth. Girl object also.
If Z depth of balls is higher than some value you will assign to girl object, it'll be behind her,
otherwise in front of her.
(or reverse)

Check also Matte Color in Object Properties.

pekka varis
02-05-2018, 12:56 AM
Thank you!

I found also Distance Dissolve. It does what I look for!

Pekka

pekka varis
02-05-2018, 05:02 AM
I am still in problems! Distance Dissolve does not affect on particles..

See this test image:
139944

I have set up one of the balls to be effeted by distance dissolve. But the particles it is emitting are 100% visible..

What can I do? I do not want to bring the girl to lightwave layout. I want to work on composition in After Effects. I am sure this is very normal situation..

Pekka

fishhead
02-05-2018, 06:52 AM
IŽd go for a hold out matte object (a simple plane with the keyed/matted sequence of the girl as a clip map) that will contribute to the rendered alpha of your Particles/Spheres. Use the sequence frontprojected from your camera and everything should work just fine...

RPSchmidt
02-05-2018, 06:52 AM
I am still in problems! Distance Dissolve does not affect on particles..

See this test image:
139944

I have set up one of the balls to be effeted by distance dissolve. But the particles it is emitting are 100% visible..

What can I do? I do not want to bring the girl to lightwave layout. I want to work on composition in After Effects. I am sure this is very normal situation..

Pekka

There are many you can do in AE that will solve your issue, but they are situation-dependent.

First, are you using classic 3d (2.5d) in AE? Or are you using a combination of AE 2.5d with C4D or Element 3d?

If you are using classic, you can use layer stacking and the Set Matte effect (if you are using AE CC... if you are using an earlier version of AE, you will have to use Track Matte) to solve your issue without worrying about the actual z depth of the relative objects.

Have two spinning ball layers and sandwich your dancing girl between them. One spinning ball layer on top, girl layer, then the other spinning ball layer.

Output an alpha render of the dancing girl. That way you can use that as a Alpha / Alpha inverted track matte on your ball layers.

Now import the dancing girl alpha render and use either Set Matte or Track Matte (for that you will need two copies of the dancing girl alpha layer) to set the alpha for your balls.

There are many other solutions for your issue, but this one is pretty fast and easy.

Hope this helps.

pekka varis
02-05-2018, 07:47 AM
Thank you!

It really look like that cos of long particle trails that I have with my balls, I just cannot do one render for layer in AE behind the girl and one in front of her. ParticleŽs live so long that they are same time at front and behind the girl..

So it looks like I really have to use this "hold out matte object" - So idea with that is that I put it on my 3d lightwave scene exaclty where I have the girl in ae - and then this "hold out matte object" gives me a "hole" to show the girl so I have 3d rendering at top layer on ae and girl below that.. right? Then the balls and particles that fly in front of the girl in lightwave are still in front of her in ae too. Like this?

Pekka

fishhead
02-05-2018, 11:45 AM
Well, basically...
Take a look at the attached scene. Maybe it helps to clear up one thing or two... There is a black and white image used as a clip map on a plane and the alpha value is set to a constant value of 0%. You can place that plane pretty much anywhere you want inside layout - It is front projected with the image i.e. locked to the "pixel space" of the camera projecting it.
Given your camera resolution matches the base footage (for instance 1920 x 1080 as in the attached scene), the dancing girl will always be exactly in the exact 2d pixel space (screen space) where it is meant to be. No matter what you do with the plane in Layout.
And everything that moves behind the non-clipped portion of the plane will have that portion "matted" in its alpha. So the girl functions as a mask for all spheres and their trails when they move behind her in LayoutŽs 3D Space and will be fully visible when in front of her. For clarity reasons the quicktime has a green backdrop but you would want to have your renders on black for cleaner compositing results.

Simple Scene and Assets: 139946
edit: these are out of 2018.0.1

Quicktime H.264 800k: 139947

I hope it helps...

pekka varis
02-06-2018, 01:21 AM
This is so good help! Thanks people.

One, thing, I am going with white background in the final video:
http://www.catchline.fi/toveri/loikka-temp9.mp4

Also the girl is filmed with white background.
What if I do the rendering with white background?

Pekka

fishhead
02-06-2018, 01:08 PM
IŽd say it depends on the quality of your key/mask.. ;-] If that is really perfect everything should be fine when you do it on white. But normally you would render your passes against black as the edges of your objects get antialiased against the background which can easily result in visible rims when composed.

See here: https://docs.lightwave3d.com/display/LW2018/Rendering+and+Compositing+-+Utilities#RenderingandCompositing-Utilities-AlphaImages
Also found this: https://docs.lightwave3d.com/display/LW2018/Compositing
Start reading at "Alpha Images"...

Try to render single fullres frames with different backdrops and play with the "Premultiply Alpha" options to see the effects for yourself. :-]

fishhead
02-07-2018, 02:55 AM
maybe this helps to clear things up even better as he demonstrates the possible issues nicely even if he does not mention Lightwave in that regard:
http://www.spherevfx.com/written-training/miscellaneous-written-training/understanding-premultiplied-images/

pekka varis
02-07-2018, 03:54 AM
I tested this and saddly I have to say that with particles & DOF & motion blur - This technigue just do not work. The look of balls and the particles emitting from them over dancing girl just looks bad. But I learned from this that I can bring in the video & clipping map of the dancing girl as front projection and just render it all in lightwave. ThanKS! I show you what I got when I am done :)