herr.ja Posted March 26, 2023 Share Posted March 26, 2023 Hello, folks, super quick question. I am quite stuping at logic of Houdini, so can you guys help me out with very essential issue? I am using vellum grain config, and I want to change size of the particles durring the animation, based on Cd attribued, which is previously defined at VOP Attrib. I am attaching short testing file, which demontrate this issue. Thank in advance for any help. pscale_issue.hipnc 1 Quote Link to comment Share on other sites More sharing options...
vicvvsh Posted March 26, 2023 Share Posted March 26, 2023 Hi, plug first output of vellum configure grain to your vop and you will see result. In other words you should set pscale attribute on geometry (1 wire ), not on constraint geometry (2 wire ). Quote Link to comment Share on other sites More sharing options...
herr.ja Posted March 26, 2023 Author Share Posted March 26, 2023 (edited) Yess, thats exactly what I was looking for! Thank you Victor, appreciate! However, I keyframed the color at VOP attribute from pure black to white, but it just takes the value from first frame and keep it for whole animation. (But I would like to change the size of the particles while the animation is running) Hows this solvable, any idea (extra advice)? Thank you so much! pscale_issue_anim.hipnc Edited March 27, 2023 by herr.ja better description of the issue Quote Link to comment Share on other sites More sharing options...
vicvvsh Posted March 27, 2023 Share Posted March 27, 2023 You should update attribute value during simulation. Dive inside vellum solver sop and check out geometry wrangle dop. pscale_issue_anim_01.hipnc Quote Link to comment Share on other sites More sharing options...
herr.ja Posted March 28, 2023 Author Share Posted March 28, 2023 Great! U saved my live once again! Even though I dont get why this particular expression, whatever, it runs! Thank you Victor! U have been really, really big help here! And maybe one last question: Can I apply the same logic on constrains/primitives? (@Cd defines how stiff the constrains should be, durring the animation) Bcs I used very same logic as u did for stiffness, but its not running. I am so sorry for this infinte bothering. I am way too old and stu*id probably. stiffnes_issue_anim.hipnc Quote Link to comment Share on other sites More sharing options...
vicvvsh Posted March 29, 2023 Share Posted March 29, 2023 You can. Just pay attention what dop data you working with. If you are manipulating with attributes on geometry from first input of vellum solver sop in dop this data called Geometry. If with constraints from second input then ConstraintGeometry. To change stiffness attribute In attached file i'm using Geometry Wrangle dop and Vellum Constraint Properties dop. In Data Bindings and Bindings tabs respectively you can see what name of data is. stiffnes_issue_anim_01.hipnc 1 Quote Link to comment Share on other sites More sharing options...
herr.ja Posted March 29, 2023 Author Share Posted March 29, 2023 Big thanks Viktor! Quote Link to comment Share on other sites More sharing options...
herr.ja Posted March 30, 2023 Author Share Posted March 30, 2023 Hi Victor, I am probably beeing ultra-stu*id but does the same method works for restlength? bcs I am keep having issues with this also. restlength_issue_anim.hipnc Quote Link to comment Share on other sites More sharing options...
vicvvsh Posted March 31, 2023 Share Posted March 31, 2023 At the start of simulation vellum solver changes order of constraints' primitives for some reason and this is why you get what you are not expecting. In this case you can use id for constraints to read value from sop to dop. restlength_issue_anim_01.hipnc Quote Link to comment Share on other sites More sharing options...
herr.ja Posted April 3, 2023 Author Share Posted April 3, 2023 Thank you very much viktor, once again! Quote Link to comment Share on other sites More sharing options...
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