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Mismatch of Alembic Scene to Render

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SteveWatson
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Mismatch of Alembic Scene to Render

#1

Post by SteveWatson » Tue May 19, 2020 7:25 am

Hi,

I'm experimenting trying to work out a method of taking a 3d scene from c4d and blender and matching with an alembic scene with the camera/objects etc. The reason is to allow placment of 2d assets into the 3d scene.

I get both the render and the alembic scene into fusion, but there is a mismatch in size, the output of the 3d renderer is smaller than then actual render from the 3d program. I've tried to find any settings about scene size but there is nothing that immediately obvious.

In the left viewer is the render, in the right is the output of the 3D renderer merged on top. All settings in fusion and blender(in this case) are 1920x1080.
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I'm sure it's something obvious I missing.

Thanks.

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ShadowMaker SdR
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Re: Mismatch of Alembic Scene to Render

#2

Post by ShadowMaker SdR » Tue May 19, 2020 7:31 am

I think this can happen when there is a FOV difference between the source file and the Fusion camera. So in one program it's horizontal, while in the other it's diagonal or something like this. 9 times out of 10 this is where the trouble stems from.

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SteveWatson
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Re: Mismatch of Alembic Scene to Render

#3

Post by SteveWatson » Tue May 19, 2020 7:41 am

ShadowMaker SdR wrote:
Tue May 19, 2020 7:31 am
I think this can happen when there is a FOV difference between the source file and the Fusion camera. So in one program it's horizontal, while in the other it's diagonal or something like this. 9 times out of 10 this is where the trouble stems from.
Hi,

there's no field of view setting in blender, but in c4d I see Field of View (Horizonalt) 53.13, Field of View(vertical) 31.417, film back 36mm

In fusion the alembic camera has angle of view 53.1301 with angle of view type horizontal - but I can't actual change any of these settings in fusion.

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Midgardsormr
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Re: Mismatch of Alembic Scene to Render

#4

Post by Midgardsormr » Tue May 19, 2020 7:47 am

When you import a camera through Alembic, the camera node is locked. If you unlock it, you will be able to change the Angle of View Type.

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Added in 2 minutes 53 seconds:
Also, there's a gotcha with C4D, described in this post: viewtopic.php?p=17873#p17873

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ShadowMaker SdR
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Re: Mismatch of Alembic Scene to Render

#5

Post by ShadowMaker SdR » Tue May 19, 2020 7:50 am

If you unlock your imported camera and set filmback --> Resolution Gate Fit to 'width' instead of 'height' there's a good chance your problem will be solved.
I just did this with a Blender file and it worked like a charm.

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Re: Mismatch of Alembic Scene to Render

#6

Post by SteveWatson » Tue May 19, 2020 7:56 am

Hi,

I knew I'd got the 3d to work in the past. I'd used FBX rather than alembic in that case.

So I exported the fbx and brought it into fusion and it matches correctly with the render.

When I compare the Alembic Camera with the FBX camera they are identical except there is a different in focal plane and the aperture heights are different.

When I change the aperture height on the alembic camera to the same as the FBX on (0.7972440944882) it matches.

Must be something weird on the camera import that screws up the aperture.

EDIT: just noticed your posts and had worked out the lock icon, changing the angle of view type doesn't work but changing the aperture height does. Thanks for pointing me in the right direction

EDIT2: Just read Shadowmaker's post properly and doing that fixes problem, again thanks.