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sweep profile control


dan_j

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Hi guys, i'm modelling some ribbon style objects using the sweep sop and i have a certain shape that i want to obtain. Is their any way i can control the scaling of the individual cross section curves which have been generated on my backbone curve??

many thanks

D

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Hi guys, i'm modelling some ribbon style objects using the sweep sop and i have a certain shape that i want to obtain. Is their any way i can control the scaling of the individual cross section curves which have been generated on my backbone curve??

many thanks

D

The easiest way would be to sweep your cross sections along your curve. Make sure skin output is off. After the sweep use and edit SOP to manipulate each cross-section how you want it and follow that with a skin SOP.

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It's not very "procedural" to think about scaling individual cross-sections. What if you resampled the input curve which is quite common. Best to use a ramp or expression to control the shape IMHO.

First place to look is the specific Operator's help card and what local variables you can use if any.

The sweep sop has several local variables. PCT is the percentage along the backbone.

You can use $PCT in the Scale parameter as is and you will get a linear scale from 0-1 along the backbone.

fit01($PCT, 0.8, 0.2) will give you a linear scale from 0.8-0.2 along the backbone.

For good control in H9.5 you can add a ramp parameter to the Sweep SOP using the Edit Parameter Interface dialog. Then use the expression:

chramp("profile", $PCT, 0)

were profile is the name of the ramp (you define the name) and the 0 is the index in to the parameter.

See the attached example file.

sweep_using_ramp.hip

-jeff

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  • 4 weeks later...

Using the sweep SOP I get the error " cannot compute the dihedral " I get this happening even with the basic video tutorial on the sweep SOP from Sidefx . What does it mean and why should I get the dreaded yellow / black error box

Rob

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  • 4 years later...

Hi I'm also getting the yellow/black stripe error saying "Cannot compute the dihedral."

Most of the search results I found over the net relate to the dihedral expression.

What could be causing the warning?

In my tests, it seems that it only appears if I'm piping in multiple curve primitives to the sweep SOP's backbone.

I attached a hip file with simple instructions to get the error.

Houdini 12.5.376

cannot_compute_the_dihedral.hipnc

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  • 4 weeks later...

nothing is breaking there, it works as it's setup

but if you want the cones to point in the direction of normals then just change tube3 orientation parm to Z

and I see no reason for the second sweeping (sweep10) where you are recreating the plane in a very hacky way from already swept profile while you can sweep both at the same time

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well in case of not symetrical cones you would need to have an up vector as well to get correct orientation

and still for your needs there is more elegant way how to control spacing between elements and still sweep them at the same time and as well to generate N and up

see the file

roll_copy_fix.hipnc

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