Loading Alembic camera

[PetkoGanev]

Hi everyone,

Can you please share your most efficient way of loading an alembic camera?

I'm working with 2 alembic files (animated object and camera) and I'm trying to Object merge them in a new Geometry node so I can use the Timeshift node to offset their animations. I can see that it's working in the viewport(I'm seeing the camera and objects move at my specified time) , but I can't think of a way to look through the "camera" from the object merge. The goal is to control the time offset of many assets using 1 node.

 I guess I'm generally asking for the best practices while working with alembic cameras. I'm currently learning Houdini and I realize my questions can be disoriented,but any help would be appreciated, there's not much about alembic cameras in the documentation.

Cheers!  

[y81r]

I have the same question.

is there a solution?

thanks

[krishna avril]

you can offset the camera using channels, I tried doing that Object merge long back, but it didn't help, As I remembered I offset camera animation using channels

there is thread in sidefx which might help you

https://www.sidefx.com/forum/topic/71882/

[y81r]

8 hours ago, krishna avril said:

you can offset the camera using channels, I tried doing that Object merge long back, but it didn't help, As I remembered I offset camera animation using channels

there is thread in sidefx which might help you

https://www.sidefx.com/forum/topic/71882/

thank you i'm trying to do that

[davpe]

actually, i was wondering about doing the same thing not too long ago, when I needed to do a camera timewarp. see the hip file bellow.

in short, you need to extract a camera transform into an oriented point (with N, up, and all that jazz), and then use rivet_SOP to drive other objects around with this point transform. works quite well for me.

cheers.

camera_timewarp.hiplc

[krishna avril]

[y81r]

6 hours ago, krishna avril said:

you guys are great, thank you so much, that's exactly what i was looking for

[davpe]

to make this info a bit more complete, you can also time offset alembics directly on alembic node by having an expression in Frame parameter. for instance $F + 10, or so...
 

[voxelfox]

Hi all,

I recently did a discussion about this for The Rookies | Rebelway FX challenge. I used a Python SOP to extract some useful data from the alembic cameras provided with the scene.

 

alembicCamScript.py
#add this code to a python sop to extract transform data from an amembic cam

#extract the world transform of the alembic xform node & mult the 4x4 matrix by a origin vector
#note --> the .node("path") is an absolute ref to the target alembic node
camPos = hou.Vector3(0,0,0) * hou.node('/obj/alembicArchive/alembicXform').worldTransform()

#creating a look nml by offseting the vec (-1 along the z-axis)
camLookPos = hou.Vector3(0,0,-1) * hou.node('/obj/alembicArchive/alembicXform').worldTransform()
camLookDir = (camLookPos - camPos).normalized()
#binding data to geo 
#.pwd() is a method for getting the active directory
geo = hou.pwd() 

#setting detail attribs onto the geo
#creating two detail attribs (camPos & lookDir)
geo.addAttrib(hou.attribType.Global, "camPos", camPos)
geo.addAttrib(hou.attribType.Global, "lookDir", lookDir)

#alternivivley uncommment this code to add a point attrib
#pnt = geo.createPoint()
#pnt.setPosition(camPos)
#pnt.setAttributeVAlue('N', lookDir)

 

Edited April 15, 2021 by voxelfox
updated link

[y81r]

On 15.4.2021 at 1:36 PM, davpe said:

to make this info a bit more complete, you can also time offset alembics directly on alembic node by having an expression in Frame parameter. for instance $F + 10, or so...
 

I'm not talking about alembic, that's quite simple, I'm talking about animated, nested null objects they are exported from another program into an fbx file on obj level.

this is the "krishna avril" method mention above.

fbx_offset.hip

[davpe]

5 hours ago, y81r said:

I'm not talking about alembic, that's quite simple, I'm talking about animated, nested null objects they are exported from another program into an fbx file on obj level.

this is the "krishna avril" method mention above.

fbx_offset.hip

I was answering Petko Ganev's original question that was about time shifting alembic camera.