# Scene Scale How to?

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Hi folks, my pipeline is Maya > Houdini> Maya
I am a bit confused about scene scale.
These question are bogging me down::

1. How much percent should I scale my objects in Maya to simulate properly in Houdini space?
2. If a real building is lets assume 260 meter high then what should be uniform size of it in maya and in houdini?
3. If I want to make some ocean sim what should be the size of the ship and the tank?

4. How can I understand this facts? Please give me some book/reference/tut if you can.

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If you are working in real world scale in Maya, then you would have to scale all your imported geometry by 0.01 in Houdini so that it's in meters. You don't need to do any scaling in Maya, just export your geo and after importing it, scale it down by 0.01. It's always useful to create a box that is 1.8 units in Y to represent the size of an average human, and compare it to your object to make sure you are using the proper scale. Then you can make your sim with that object and after you are done with Houdini, simply scale the outgoing geometry by 100 before writing it out, it's only important that you are dealing with real world scale when you are doing any simulations, after that you can go back to the Maya size. You should get your geometry back in Maya with the exact size as when you initially exported it.

Maya is in centimeters (if you use the default settings) and Houdini in meters, so 100 units in Maya is equal to 1 unit in Houdini. Your 260m building would be 26,000 units in Maya. When you export in Houdini, you would set the uniform scale to 0.01 (which would make it 260 units in Houdini). Before exporting back, add another transform sop and set it to 100.

Knowing this you can probably calculate how big your ship is because I have no idea if you are dealing with a boat or a 100m cargo ship. You can then set your tank to be the according size in relation to the size of your boat.

Finally, I don't know of any places where you can learn about this, other than online forums or word of mouth. Most tutorials never show how to deal with geometry across packages. I guess its one of those things that you figure out once and never forget.

Edited by Jero3d

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Thanks a TON for the detailed explanation. Just one thing:

Then you can make your sim with that object and after you are done with Houdini, simply scale the outgoing geometry by 100 before writing it out, it's only important that you are dealing with real world scale when you are doing any simulations, after that you can go back to the Maya size. You should get your geometry back in Maya with the exact size as when you initially exported it.

It means after the sim cache, I will re-size it right?

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No problem! Yes after your cache, you can add a transform and scale it by 100 right before you write out your alembic.

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No problem! Yes after your cache, you can add a transform and scale it by 100 right before you write out your alembic.

Thanks a LOT!

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On 4/14/2016 at 3:25 PM, cgvirus said:

Hi folks, my pipeline is Maya > Houdini> Maya
I am a bit confused about scene scale.
These question are bogging me down::

1. How much percent should I scale my objects in Maya to simulate properly in Houdini space?
2. If a real building is lets assume 260 meter high then what should be uniform size of it in maya and in houdini?
3. If I want to make some ocean sim what should be the size of the ship and the tank?

4. How can I understand this facts? Please give me some book/reference/tut if you can.

So I found out that 1 cm in Maya = 1 meter in Houdini (Maya's mm are Houdini's cm). So if you want to not worry about scaling at all, if you simply build in Maya's centimeters. This is super stupid, but it might help simplify your process

ALSO I learned that by exporting from Maya in FBX format (with the setting at meters), when you import it to Houdini (File>Import>Filmbox FBX), there is no scaling difference whatsoever, which is pretty great

I'd probably even then work with cm or feet as my base unit in Maya, though, so I can easily scale the object up and work reasonably with finer details; as you might know already, small details can be annoying to work with when your unit is too small and the camera starts clipping through the geometry =P

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