dan_j Posted July 2, 2008 Share Posted July 2, 2008 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 Quote Link to comment Share on other sites More sharing options...
SpencerL Posted July 2, 2008 Share Posted July 2, 2008 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. Quote Link to comment Share on other sites More sharing options...
old school Posted July 3, 2008 Share Posted July 3, 2008 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", $PCT, 0) were profile is the name of the ramp (you define the name) and the 0 is the index in to the parameter. See the attached example file. sweep_using_ramp.hip -jeff 2 1 Quote Link to comment Share on other sites More sharing options...
dan_j Posted July 7, 2008 Author Share Posted July 7, 2008 Sweet, nice one old school....that works like a bloody charm. Many thanks D Quote Link to comment Share on other sites More sharing options...
rob Posted August 3, 2008 Share Posted August 3, 2008 Using the sweep SOP I get the error " cannot compute the dihedral " I get this happening even with the basic video tutorial on the sweep SOP from Sidefx . What does it mean and why should I get the dreaded yellow / black error box Rob Quote Link to comment Share on other sites More sharing options...
galagast Posted May 9, 2013 Share Posted May 9, 2013 Hi I'm also getting the yellow/black stripe error saying "Cannot compute the dihedral." Most of the search results I found over the net relate to the dihedral expression. What could be causing the warning? In my tests, it seems that it only appears if I'm piping in multiple curve primitives to the sweep SOP's backbone. I attached a hip file with simple instructions to get the error. Houdini 12.5.376 cannot_compute_the_dihedral.hipnc Quote Link to comment Share on other sites More sharing options...
Elias Posted June 1, 2013 Share Posted June 1, 2013 Is it possible to control the backbone in a similar fashion? I'm trying to control the roll in the sweep using point attributes on my backbone curve but I can't get it to work. curve_roll_attribute_001.hipnc Quote Link to comment Share on other sites More sharing options...
anim Posted June 1, 2013 Share Posted June 1, 2013 since you are using more than one backbone, you need to make roll a vertex attribute so you can access it by backbone ID and vertex number ($PATH, $PT) like this vertex("../Curves", $PATH, $PT, "roll", 0)[/CODE]curve_roll_attribute_fix.hipnc Quote Link to comment Share on other sites More sharing options...
Elias Posted June 1, 2013 Share Posted June 1, 2013 Fantastic! Thanks! Quote Link to comment Share on other sites More sharing options...
Elias Posted June 3, 2013 Share Posted June 3, 2013 (edited) Sorry to continue to hi-jack this thread but what's breaking here in my file? roll_copy.hipnc Edited June 3, 2013 by Elias Quote Link to comment Share on other sites More sharing options...
anim Posted June 3, 2013 Share Posted June 3, 2013 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 Quote Link to comment Share on other sites More sharing options...
Elias Posted June 5, 2013 Share Posted June 5, 2013 The reason for the hacky recreation is that I want to be able to control the distance between the copied elements. I made a new file to better show what orientation I'm after. roll_copy2.hipnc Quote Link to comment Share on other sites More sharing options...
anim Posted June 5, 2013 Share Posted June 5, 2013 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 Quote Link to comment Share on other sites More sharing options...
Marc Posted June 5, 2013 Share Posted June 5, 2013 Coming in way late to this zombie thread, but I didn't see anyone mention tha Rails SOP. Which would give you what you need no? Quote Link to comment Share on other sites More sharing options...
Elias Posted June 6, 2013 Share Posted June 6, 2013 Thank you Tomas! That's elegant indeed! Quote Link to comment Share on other sites More sharing options...
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