Houdini Alembic camera import sizing

[charliejh]

Hi,

rookie question:

Why is it that when I import an Alembic camera from Maya into Houdini, it makes the whole scene insanely large.

The camera moves a massive distance and as such I am forced to create massive grids and simulations with attributes set to numbers in the thousands.

This is really hard to work with and creates clipping problems if you move close to the geometry, which i cant seem to fix even in display options.

I'll attach the scene file and the ABC camera file (not sure how to attach them in the same file). So import the ABC file yourselves  Basically the camera is leading a car straight along a road and there is going to be a dust storm in the background and also dust trailing behind the car.

If you convert the tube in the scene to Billowy Smoke, it comes up with a warning saying 'Object level scales detected. A new object has been created to convert to world space'. Which I suppose is a way of saying 'Hey, your scene is super massive and could be fixed somehow'.

I'd like to know if there is some way to import the same camera, but have the scene scaled to a suitable size so i dont have to put huge numbers in while experimenting with smoke, particles etc.

 

Thanks

 

Scene01.hipnc

Camera Alembic.abc

[tamagochy]

Maya work units - cm, houdini - m. Just scale it down by 100.

[charliejh]

So I went into Preferences, Hip File Options and changed Unit Length (m) to 0.01 (or centimetres).

This hasn't seemed to have done anything. Even if I create a new scene and re-import the camera, I still have to make a grid (nearly 1000 units in X, Y and Z for scale) just to cover the length that the camera travels.

I must be missing something here?

EDIT: So iv had a look at the camera in Maya, it moves about 22,000 units (cm's) in total. So when I take this camera and put it in Houdini, its moving 22,000 METRES right??

So to make this reasonable to work with in Houdini I need to divide this by 100, so the distance is about 220m. This should be done in Hip File preferences right? 

Can I scale the camera movement so It still moves the same and rotates the same, but over a shorter distance? Or can this be done in Houdini? I dont know how to edit the camera keeping in mind it is an ABC file.

Edited August 9, 2016 by charliejh
update

[martinkindl83]

19 hours ago, tamagochy said:

Maya work units - cm, houdini - m. Just scale it down by 100.

just make sure if you scale the camera alembic node by 0.01 that you go and scale the camera node it self by 100.

otherwise you will have lot of render errors in final image, shaders and lights will not work properly

 

you have to end up having final camera scale of 1 (compare camera icon in viewport to native houdinis camera icon), they have to match.

[tamagochy]

I link camera to null and scale down null. 

[martinkindl83]

54 minutes ago, tamagochy said:

I link camera to null and scale down null. 

which is wrong

you need to scale only transforms

 

[sekow]

plug in a null into the alembic archive sop, scale the null to 0,01.

use a fetch sop to get your camera transforms, plug that into a blend sop. in the blend sop deactive sclx scly sclz and plug that into a fresh cam. reference all camera params you need. when you're real smart wrap everything into a digital asset and be smart with your references so you just need to pick your original camera. hope that helps

[michael]

or use the alembic functions directly

http://www.sidefx.com/docs/houdini/hom/abc_extensions

[tamagochy]

5 hours ago, sekow said:

plug in a null into the alembic archive sop, scale the null to 0,01.

use a fetch sop to get your camera transforms, plug that into a blend sop. in the blend sop deactive sclx scly sclz and plug that into a fresh cam. reference all camera params you need. when you're real smart wrap everything into a digital asset and be smart with your references so you just need to pick your original camera. hope that helps

If you can make scene with example would be good. Because what i made from your explanation is not working.

[sekow]

been a while, but in case you need something try the attachment. its working for me, and how I work. just put in the path of your alembic cam and the desired scale.

the asset while fetch all needed camera params like fov and so on...camera_to_scale.hda

[charliejh]

Hi sekow,

In your example file, I dont see where you have placed the initial alembic camera? If my alembic camera is on object level, do I placed the fetch and blend nodes on object level and connect them to the alembic file? Or do I go inside the alembic file and then create the nodes?

Thanks

 

Charlie

[sekow]

just point the cam_path parameter to your object level camera and adjust your wanted scaling.

 

[charliejh]

Ohhh I didnt realize I could just copy and past the node into my project haha. You've solved a 3 day problem thanks mate