mjL Posted January 7, 2015 Share Posted January 7, 2015 I'm hoping someone can help me out with creating a gradient descent algorithm in VOPs (it might not be possible?). I've be trying to reverse engineer this - https://vimeo.com/60606152 which is done with Rhino. I can get as far as the point where you need to push the points back to the surface (timecode 2:49 in the video). They do this using a surface CP node (which as far as I can tell imports the vectors for the nurbs surface?). Is the there an equivalent way of doing this in VOPs or am I going about it in the wrong way? Any help will be much appreciated. Thank you, Mark GradDescent_01.hip Quote Link to comment Share on other sites More sharing options...
kleer001 Posted January 7, 2015 Share Posted January 7, 2015 I don't have any help to offer, but I was just thinking about this gradient the other day. How do you find the preferred path of a ball rolling down from every point? Quote Link to comment Share on other sites More sharing options...
kleer001 Posted January 7, 2015 Share Posted January 7, 2015 No, sorry, I lied. I did figure it out, lol. Just a few old school SOPs. Check it out. downGrad.hip 1 Quote Link to comment Share on other sites More sharing options...
petz Posted January 7, 2015 Share Posted January 7, 2015 I'm hoping someone can help me out with creating a gradient descent algorithm in VOPs (it might not be possible?). I've be trying to reverse engineer this - https://vimeo.com/60606152 which is done with Rhino. I can get as far as the point where you need to push the points back to the surface (timecode 2:49 in the video). They do this using a surface CP node (which as far as I can tell imports the vectors for the nurbs surface?). Is the there an equivalent way of doing this in VOPs or am I going about it in the wrong way? Any help will be much appreciated. Thank you, Mark it´s fairly easy to do in houdini. the attached file should help. hth. petz GradDescent_02.hipnc 2 Quote Link to comment Share on other sites More sharing options...
mjL Posted January 7, 2015 Author Share Posted January 7, 2015 Thanks guys, really helpful. Petz - more advanced than I understand but it'll give me a good reason to brush up on my VEX in order to implement the rotation part like in the example video. Thanks again Quote Link to comment Share on other sites More sharing options...
paxsonsa Posted January 7, 2015 Share Posted January 7, 2015 (edited) it´s fairly easy to do in houdini. the attached file should help. hth. petz Petz this little piece of VEX is brillant! Here is VOP SOP implementation as well with Petz GradDescent_03.hipnc Edited January 7, 2015 by paxsonsa Quote Link to comment Share on other sites More sharing options...
Pazuzu Posted January 7, 2015 Share Posted January 7, 2015 (edited) Wow Petz!! Nice technique!!But why this vector? (-@N.z, 0, @N.x), I mean were did you find this nice vector shuffle to help derive the gradient with N? Thank you!! --Edit-- Ahh ok, I get it!! Its the result of a cross between N and an up vector like (0, 1, 0). Sorry for the dumb question!! Edited January 7, 2015 by Pazuzu Quote Link to comment Share on other sites More sharing options...
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