This trips me up every so often so I thought I'd finally try to sort out the right way to fix it.

I create a geo object NOT at the origin and use it as a POP source. Then I create some collision geo, say a building, at the origin. When I bring the building into POPs, its position is transformed to the same position as the POP source (the collision object is moved to POPs world space I think) and the emitted particles immediately collide.

What I want to do is move the collision geo's position in POPs back to its original position in worldspace.

I've tried to apply the negative position of the POP source to the collision geo in DOPs using ObjectPosition and Position but no luck.

This isn't urgent but I would like to wrap my head around object transforms so any help is much appreciated.

I put together a quick HIP file attached.

ideal way to transform your objects is inside the geo level, its not a preferred way to transform your geo's at object level


pops can be fixed by doing the following steps
unlock your popsource go inside, go inside sop solver , there is an object merge node at the top call context_geo, change the transform to Into This object.

it should be like this by default I believe but if not you can do it manually

but I never do my transforms at object level because inside dops world it reads the information from where your input is coming in not from one level above it.


so best fix is to create a transforms node before you are inputing the nodes to your popnet rather than at object level

Use an object level dopnet, this serves as a unifying space to into which to transform. Alternatively, create a new object to serve as the ‘sim’ object, and merge all the inputs into it using object merges, and connect to a popnet there.

Object level transforms are useful because they don't require cooking geometry as if it were deforming. So many fx artists miss out on great the optimization and organization that come from using Object nodes effectively.

Thanks rizviali and jsmack, much appreciated. I've rebuilt the test scene a couple times following your comments and have a much clearer idea of setting DOPs up now.