Hello there.

I have an object and im trying to find its pivot point position on ABSOLUTE world coordinates (the object is already a child of another object).

What im trying to do with this is a simple “Point Constraint” with CHOPS. if anyone knows of a better way to do a point constraint, please let me know.

Thanks

Rudy

A simple point constraint might be easier done with a Null as your point and then using the Blend Object. Turn translates off from the first parent and turn them on for your second parent.

If you want to get at the world position through CHOPs, then the Object CHOP will help. Otherwise, using the vtorigin() expression function will work if you want to use expressions.

a little note of warning on the origin, vtorigin etc functions - I've used them a bit and it seems like they will only return the ‘shortest’ path to the values….
given brand new foo1 and foo2
rotate foo2 by 359 in Y
vtorigin(“/obj/foo1”, “/obj/foo2”) will return :
NOT

doesn't mean they're not cool though
Blend Object is your best bet for constraints

Hi Edward.-
Hey . Thanks a lot for your reply.. The blend op really did it.

I tried using the object CHOP but it wants two inputs before the CHOPS viewer displays anything. What do I need to put into the 2nd field to get the world position of the first object?


Hi Arctor-
So, you are a rigger? do you do a lot of character work? Im migrating from Maya to houdini and I need some help from someone who has solid knowledge of rigging in houdini.

Thanks a lot to both.

Rudy

you could try a null or something just sitting at the origin as your reference object…
the object CHOP needs to compare the thing you're interested in with something else….like if you asked how far away is it and I said “50”…but 50 what? and from where? better to say “50 miles from me”

I'm just started at C.O.R.E as a rigger….but I haven't been trained yet so I'm doing both diddly and squat…and I come from Maya also, so I'm trying to figure things out as well …one thing I can say is that it's not always a good idea to simply ‘translate’ an idea or technique from Maya to Houdini….sometime there are better ways to do things with Houdini's own tools and sometimes things are just not possible to do the same way…
glad to see another person around asking questions about Houdini's character tools…that way we'll all learn more

I did try placing a null at the origin and called it “world”. However the CHOP operator calculated a LOT slower than the blend, so im sticking with the blend for know.
You are right.. there are many Maya techniques that i've tried to implement in houdini, most of them wont work the same way and thats where all those hours of reading and practicing come in hany to solve those peroblems.

Im almost done with this rig. Its quite simple because I wanted to at least get SOMETHING to work the right way before I attempt creating any complicated riggs. I will make this rig available for everyone in the forum to play with and to get feedback

Thats all for now. Good luck a C.O.R.E.

Rudy

thanks.
please do post the rig…it's always great to see how other people think and solve problems

Arctor, I think you meant vrorigin as opposed to vtorigin (note the r vs. the t). It's a good point though about vrorigin.

The Object CHOP doesn't need any inputs if you give it the two object paths in the parameters. It's probably slow interactively because the default behaviour is to cook for the entire animation frame range. If you put $T in the Start and End parameters, it will cook plenty fast.

I did try placing a null at the origin and called it “world”. However the CHOP operator calculated a LOT slower than the blend, so im sticking with the blend for know.

In the Channel tab of the Object CHOP you should put $F in the Start and End fields. Otherwise the Object CHOP calculates the distance for the whole range of the animation and it's slow.

Dragos

If you put in $F, then make sure the Units on the third page is also set to Frames. I think by default, they're in time which means using $T instead.

I have just read this thread after having trouble doing just this.

1 object chop is targeting null_A, and the other object chop is targeting null_B
Both reference a world_null and there fraim start and finish rainges set to $F
null_B is parented to another null just to prove it is more than just sibling objects working together.
then added a constant chop with one value of .5
wired that value as the first input of a blend chop folowed by the object chops
then piped that into an export chop sending it to the object that i want to stay between the other two.

OK now…
Using chops I want to make an operator type that simply dose this so you only have to deal with one sop much like the IK chop

I have collapsed it into a subnet and created an object type from it.
I am having trouble linking the target objects to an “operator path” paremeter in the Operator Type Properties /parameters tab.

I made a simple sop operator type with an object merge inside and attempted to link up the target object to an “operator path” paremeter in the Operator Type Properties /parameters tab with no success ether

Any help on this topic?

Not quite sure if you have two questions there. So does your chop network work? In your description, you didn't mention changing the units to frames which you would need to do.

As for how to export operator paths to custom operators, here's how to do it in 6.1.208. (It's easier in later versions.) In the Parameters page of the Operator Type Properties dialog, click on the plus (+) button to the right of the “Create New” menu. Select the operator path parameter you wish to export in the tree dialog that comes up and then hit Accept. Hit Accept again in the Operator Type Properties to save your custom operator.

the $F stuff is cool
I am kinda running this thread on odforce and here

this is what I have found…… basickly i think the blend opp is 3 times as fast
http://odforce.net/forum/index.php?act=ST&f=18&t=1779&s=051cec7efee2a102b96a354e4cbe04b8 [odforce.net]