Conrad Olson
Forum Replies Created
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I forgot to add “match lens distortion”. This should be done after the output of the 3D setup or after the 2D track.
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This is how we would do something like this on a feature film:
Camera track each shot, regardless of the type of camera move, making sure that the cameras all end up in the same relative postion to each other.
Build some 3D geometry for the room and the extra ceiling extension. This could be a massively complex and detailed 3D model, that gets textured and rendered from Maya, or if we are doing the simpler 2.5D approach we will have a matte painter paint up stills and apply them to cards in Nuke (but you can do the same in AE). You would have a card for each wall and then the ceiling. If you can use some frames from your original shot to create this painting it will help you get the colours to match.
Creating a solid 3D setup and getting camera tracks takes time at the beginning of the process but once it is done you can quickly get all of the shots into the same place, and if there are changes to the matte painting later you can just update the setup and drop it into all of the shots.
We will then drop the camera for each shot into the 3D environment and you will get the correct view. Remember that if you are using the card/matte painting solution there will be no parallax within the painting. If it is far enough away this wont matter.
Then take the output of this 3D setup and composite it with the rest of your shot as if it was any other kind of footage.
If there is a defined edge to the top of your set and the start of the green screen, like a line of bricks or a ledge, use that as the joining point between the set and the extension. If it is a smooth texture that you want to continue you might need to create a feathered edge to hid the seam. This will probably require roto but if you have a 3D setup you can render a feathered matte from there that will work for every shot, without the need need to roto each one.
Other things you will need to do to sell your composite are:
*match the black levels to your plate
*match any grain or noise to your plate
*match the motion blur
*add any interactive lighting to your extension
*match the depth of field—
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Create an expression control that lets you control the retime.
Create a duplicate camera, with no animation
Hook it up to the animated camera with an expression that references the position of the original camera, from the frame specified by the expression control.
Keyframe the expression control to do the retime.
The new camera will be able to get values from in between whole frames from the original camera based on the animation curve.
I don’t have After Effects in front of me and haven’t used expression in it for a while so can’t give you an example but this is how I would set it up.
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I wrote a blog post about how to do something similar in Nuke. You might be able to adapt it: https://conradolson.com/a-simple-nuke-expression-example
Basically you need to create an effect control slider that acts as a multiplication factor for the stabilization data. Then you can animate that slider between 0 – 1 to dissolve in the animation.
If you have two sets of data that you are mixing between I think you could take the second data and multiply it by the inverse of the slider (1-slider). That way you will get all of one data at 0, all of the other data at 1 and a mix in the middle.
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Why don’t you render out an image sequence from AE and then use Photoshop to make them into an animated gif. Don’t need Flash player then.
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I feel like they are too shiny and that the reflections don’t match the environment.
Also, as a comp note, the black levels in them is too dark and blue compared to the background. I’m looking at the wide shot at 40 seconds. The transfomer on the left has too much contrast. They also need contact shadows to sit them into the plate.
It’s a good test of Element though.
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Black levels and colour cast, like Ted suggested, are the most important.
There is a haze to things further away from the camera, and due to how different wavelengths of light are absorbed by the atmosphere object in the distance usually have a blue tint to them.
When it comes to the black levels, the darkest shadows in your foreground should be the same level and tint as the darkest shadows at a similar distance in your background. As things get further from the camera the diffusion caused by the atmosphere means that the blacks don’t look as dark. You can see this in your plate. The trees nearest the camera have darker shadows, and therefore more contrast, than trees further away. You need to work out where in depth your kid should be and try to match those levels.
Another good trick to quickly make something sit in with a background is to add some light wrap from the background over the foreground. Take the alpha of your forground and blur it. Then take another copy of your alpha and use that to mask the blurred version. This will give you a soft feather inside the shape of the foreground. Then take a copy of the background, blur that a bit, mask it with your feathered alpha and put this over your foreground. Adjust the blur of the first copy of the alpha to control how far this wraps around the foreground and the opacity to control how strong it is. In this case you won’t need too much, but even a tiny amount helps.
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Do not change the resolution of your composition. It will effect and position values in your transforms and scales.
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Shadows in 2.5D situations are never as straight forward as you would like.
I don’t know if you can use the same projection techniques in After Effects that you can do in Nuke but if you can here is what I would try:
Work out where in the 3D space the actor should be standing and position a 3D layer at that point.
Key they actor so he has an alpha channel.
Then project him from the tracked camera, onto the card. This will give you the actor in the correct position in the 3D space and at the correct scale. This is that part that I could do in Nuke easily but I don’t know how you would go about it in AE so someone else on here will need to chime in. I’d like to learn if this can be done in After Effects.
Once you have the actor on the card you can use a light and that card to cast a shadow onto the other geometry in the scene. You could either use this as part of your render, or render it separately and use it as a mask to grade your BG through. This is where AE wins over Nuke at the moment. You can’t cast shadows in Nuke so this doesn’t work.
The short coming of this technique is that that card is only 2D in a 3D space. The shadow will look great if the light is from the front or the back, but it won’t work at all if the light is 90 degrees to the card because there is no volume.
I most cases we use 2D tricks to create these kind of shadows. If we need a more accurate version we would get a match moved digi double of the actor, place it in the 3D scene, and render a shadow matte from the 3D package.
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