Hello all,

I am a little confused by the options in the object merge sop. Specifically the ‘Transform’ and ‘Transform object’ options. Please see the attached hip file.

This is what I understand the various options to mean:-

None:
Merges the box at its sources sop space position, regardless of any obj level xforms on the source obj.

Into this object:
Takes into account the sources sop level and object level xforms and its own object level xforms and dynamically adjusts to object merge the box at the exact position of the source.

I think I got these ones down. Please correct me if I am wrong. The option which confuses me is ‘into specified object’:-

Into specified object with ‘Transform object’ blank:
Does the same as ‘None’. Grabs the box at the sop level position of the source regardless of obj level xforms on the source.

Into specified object with ‘Transform object’ .
The same as specifying ‘Transform’ as ‘Into this object’.

Into specified object with ‘Transform object’ referencing box3:
This is the one that confuses me. If I use ‘Box_3’ as the ‘transform object’, the object merge seems to ignore any sop space xforms for ‘Box_3’ and then apply the inverse of any ‘Box_3’ obj level xforms. For example if I set ‘Box_3’ ty = 5 at obj level, the object merged box then merges as if it has a -5 xform somewhere. I'm not saying this is incorrect behavior, I'm just confused as to why specifying a ‘Transform object’ means it will apply the inverse of the specified objects obj level transform.

Can anyone shed some light on this? Also if I have stated anything incorrectly I would welcome someone to set me straight.

Many thanks,

Dexter.

Hi Dexter,

I think that is a bug on “Into Specified Object”.
It will just invert the value of the Obj translate.

cheers

it's no bug, that's what it does, it transforms the geo into specified object's space

if Into This Object makes sense to you
which takes the geometry in it's local space (G), it's Object transform (B) and This Object's transform (A) and does:
G * B * inv(A)
to transform G from local space of B to local space of A

then Into Specified Object does the same thing just instead of This Object's transform (A) is Specified Object's Transform
so if you put .. into Transform Object path (to point to this object), you will get the same result as Into This Object
but yeah, it is applying the inverse of A by default as that's the math behind such space transforms as you need to “remove” the object's transform to get the geo in local space of such object, hence the inverse