Forums Technical Discussion point velocity in DOP

point velocity in DOP

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Soothsayer
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I have a RBD point object and I am trying to set the initial velocity with a sop attribute.

I made a vector attribute called usevel and gave it a y component of 11.

If I check the detail pane in the DOP network I can see that usevel is indeed set to but it does not have an effect.

If I set the velocity of the initial state manually (in DOP) then it works.

Why then does it not use my attribute supplied value?

Attachments:
usevel.hipnc (107.0 KB)

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sanostol
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just use v as attribute name and they get the desired velocity
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Soothsayer
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OK. cool, thanks!

(but why didn't my method work?)
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probbins
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For you method, since you are importing the value from sops, I believe Dops reads only the 1st frame of information unless you “Set Always” so that the sop data is read per frame.
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sanostol
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mh, I must be blind, but I can not see that there is any node that tells houdini what to do with usevel. is it a special attribute?
usevel is the name of the integer attribute that decides where to get the velocity from, but I think You can not drive it from by pointattributes
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Soothsayer
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Well, if you look in the details pane of the dops network it sets the usevel value to the one you enter in the initial veocity, and uses that velocity. If I set it from an attribute in sops it displays the value correctly but doesn't use it. And hovering above the parameter gives the name usevel.

Soo….I dunno. I'm just trying to understand how the dops *think* but it makes little sense to me. :shock:
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Soothsayer
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here are screenshots

Attachments:
usevel.jpg (18.0 KB)
usepara.jpg (16.5 KB)

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sanostol
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1. this vector only exists, because You tell the dopobject to copy all parameters, so they are copied onto the object, but houdini can not use it.

2. usevel is another parameter that only tells houdini where to get the velocity from. click on the edit parameter button on the object and see, that there are 2 independent parameters, integer usevel and vector v.

cheers
Martin
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