Exit
  • Global community
    • Language:
      • Deutsch
      • English
      • Español
      • Français
      • Português
  • 日本語コミュニティ
  • 한국 커뮤니티
0

Using 2 different cameras in same comp?

Community Beginner ,
Sep 15, 2019 Sep 15, 2019

Hello fellow AE'ers

I'm doing a projection mapping, where I need my camera to be "straight on" (I have set up a cam with a very large zoom) to not have any perspective. The projection has 3 layers with a foreground, midground and background. To have light and shadows interacting with all 3 layers in the scene in After Effects, I'm having the straight on view, so I know it will match when it gets projected onto the 3 surfaces.(that looks like an old theater, with a curtain in front, some scenography in the middle and a curtain in the back, that will be projected on)

However, say I want a 3d model going from one side to the other with some perspective - is there a way I can have a 3d element moved around the the comp but with perspective and not just "straight" on, so that it gets a little more dynamic?

Also if I want to "extude" some elements on the front curtain and give it perspective, can I do that for only the 3d element, but still making sure that my 3 layers are "straight on"?


Any direction would be much appreciated,

Best,

 

 

759
Translate
Report
Community guidelines
Be kind and respectful, give credit to the original source of content, and search for duplicates before posting. Learn more
community guidelines
LEGEND ,
Sep 15, 2019 Sep 15, 2019

Not sure what you're getting at. si9nce AE doesn't have any genuine orthographic cameras, there will always be some perspective, regardless of how far you zoom out. Of course you can always emphasize it by animating the objects themselves or applying distortion effects to the 2D output. Generally, though, I would stay away from this kind of workflow in AE. It's simply not cut out for this kind of work. even the slightest bit of additional animation can make things look totally whacky at "infinite" zoom levels. This really sounds like you either need to think more about your project structure in AE or do it in a 3D program right away. More to the point it seems to me that at the very least you need to keep your proscenium setup in a separate comp and animate your objects in another with a more conventional camera, then mix everything as 2D layers.

 

Mylenium

Translate
Report
Community guidelines
Be kind and respectful, give credit to the original source of content, and search for duplicates before posting. Learn more
community guidelines
Community Beginner ,
Sep 15, 2019 Sep 15, 2019

Thanks a lot Mylenium.
I'm doing a "paper cut out" projection, where i project on layers of surfaces.  
I'n my AE i'm basically just using "front" to get it straight on and then pulling back the layers that are in the midground, background etc. 
Mixing with the 2D layer, how do I do that? 
My scene looks perfect and right with the "straight on" cam - but as you say it's when i add 3d elements.  So it would be perfect if I can add those from another comp, using another perspective.


Translate
Report
Community guidelines
Be kind and respectful, give credit to the original source of content, and search for duplicates before posting. Learn more
community guidelines
Community Expert ,
Sep 16, 2019 Sep 16, 2019
LATEST
To give you much more guidance I need to see a screenshot of your comp showing multiple views and have a better description of what you are trying to achieve. I also need to see a sketch of the venue showing the walls and the projector location.
Translate
Report
Community guidelines
Be kind and respectful, give credit to the original source of content, and search for duplicates before posting. Learn more
community guidelines
Community Expert ,
Sep 15, 2019 Sep 15, 2019

If there is to be no depth between the background images, the Theater Stage, then there is no reason at all to have those layers be 3D. You can just layer them. 

 

If you want a 3D object to appear to have depth then you need to use a standard camera with a standard lens. The default camera fairly closely simulates the normal perspective you get when viewing things from a normal viewing distance.

 

I think that the biggest source of your misconceptions is that focal length determines perspective. Perspective is only dependant on camera position. There is no way for you to realistically recreate the perspective on any projected image for a viewer on the left side of the screen and a viewer on the right side of the screen at the same time.

 

If you are projecting on a flat surface just set up the scene to look the way you want it to look and don't worry about anything else.  If you are projecting onto different surfaces you need to set up your layers so the distance from the projector to the surface is at the same ratio as the distance from AE's camera to the layers intended for each surface. Did you follow that?

 

Let's say that the surface you are projecting on has 3 planes, one 200' from the projector and on the right side of the frame, another 250' from the camera and taking up the center 1/4 of the frame, and the third 3000' from the projector on the left side of the frame. Assume that all of these surfaces are perpendicular to the projector.

 

If you wanted to be absolutely accurate you would go to the location and set up a camera in the same position as the projector, adjust the focal length to frame up the shot so that it just includes the surfaces, put some reference in the shot that you can measure, like a 6' tall assistant, then take that shot and record the data. 

 

If you want to just get close just create a default camera (50mm lens), add it to the comp, then double the Z distance from comp center.

 

Now add 3 solids to the comp - all the same size and position them at the same relative distance from the camera. IOW, the layer on the right would be set to 2000 pixels in Z, the layer in the center would be at 2500, and the one on the left would be at 300 pixels. Now you scale all of the layers to make them the same relative size in the frame. You can use an expression to do that. The last step is to crop each layer so they match the surfaces of the building. This is much easier to do if you have a photo taken from the same position as the camera. Now you have your reference planes set up and you can start creating your scene. 

 

I hope those explanations make sense. I've done this kind of thing many times and the only time I ever worry about setting up a 3D environment is when the surfaces are in different planes. Every time I have done a job like this I go to the location and take a reference image from the projector's position. That is the only way I know of to get things properly lined up.

Translate
Report
Community guidelines
Be kind and respectful, give credit to the original source of content, and search for duplicates before posting. Learn more
community guidelines
Community Beginner ,
Sep 16, 2019 Sep 16, 2019

Thank you so much Rick for this very detailed explanation and insights.
I’m learning and I’m loving it! So thanks for that.

I get what you mean in terms of setting up a 3D environment, I'm using lights quite a lot hat moves around between the layers and has a falloff, and looks very realistic. For example I have some elements in my middleground that casts shadows on the background. I have then some other paper cut objects closer to the background that also casts shadows on the background, giving it all a lot of different depths. Will I be able to achieve this with 2D layers?


I have set it up so the ratio between the 3 layers matches the real life sizes. However that means right now, using a 1080p Comp, my foreground is the largest. When I render out, I intent to take in the whole comp in a new comp, scale the mid ground to 1080p width, use “shadow only” on the foreground and hide the background, and render so I get a maximum space for the foreground. The same goes for the background (that right not is only half of the screen).
Here I also will scale up the whole comp, shadows only for foreground and mid ground and have the background filling out the 1080p space. So I basically get 3 videos each 1080 p, that will projected on each surface.

So basically I'm only using the 3d layers to get the light to interact between all 3 layers, so shadow that is being cast form the middleground will hit correctly on the background etc.

When rendering out, they will each have the same size. (by scaling the whole comp)

 

Then I’m using a stencil to “cut out” the shape of the layer and render out in process 4444 or something that includes alpha.

You input has been very much appreciated and any thoughts or further direction would be much appreciated.

Translate
Report
Community guidelines
Be kind and respectful, give credit to the original source of content, and search for duplicates before posting. Learn more
community guidelines