Setting Up a Glue Constraint Manually

in this video I would like to discuss how to set up glue constraints from scratch as we did in class just this past week at both Becker and Leslie we were pretty much in sync in both courses so what I have here is a volume volonoff rack sure so the ISO offset the scatter and that I'm using those volume scatter points to fracture or to drive the von Oy fracture so the first thing I want to do here is set up two nulls one for the geometry coming out and one for the constraints coming out so I'll right click in here and I'll type in and you ll for null so I'll put one null here and I'll title this one out geo whoops GGO frac for fracture and then I'll just alt drag on that null to create a new one to create a copy and in this new one I'll just name this one out Co NS for constraints so now I'm ready to generate the RBD simulation so what I'm gonna do is put my display flag on the out geo fracture node this null is remember whatever node has the display flag on it that's where Houdini is going to make the rest assemble and stop import nodes for the simulation so I'll put my display flag there come back up to the top level I'm going to go over to my rigid shelf right there rigid bodies and I'm gonna click on the RB d objects and that will give me a Doppler --k and while I'm here I might as well just jump over to the collision shelf and add a ground plane so now I have a ground plane here also and if I run the simulation I should get some rigid body fractures just falling all apart so now I'm ready to set up for the glue constraints so there's two places we need to add nodes we're gonna add nodes in the box object itself the simulated object and also in the Dopp Network so I'll go to the geometry Network first where the box is and I'm gonna build this off of oh jeez didn't even realize I never switched this this this null on to the casual constraint output there it didn't it hasn't affected anything yet but it would at this point so I didn't when I copied this node using the Alt key I forgot to wire it in here so make sure you do that now okay so what we need to do first is create the glue constrain that's what's going to hold everything together so that's going to be an attribute that we have to create here using the attribute create node so I'm going to create an attribute create so I'll right click in here and choose attribute create and I'm gonna place this before the The Outlaw because the out mole is what I'm going to reference over in my top Network so I'll wire these in here and in this attribute create the first thing we want to do is change the name we need to tell it to be a constraint so I'm going to type in and this this name has to be specific this is not one that we can choose our own name so I'm going to put constrain underscore name constraint name and now with the von Oy fracture with with glue constraints in general they are on the primitive level not the point level so the class here needs to be changed to primitive and the type needs to be changed to string because what we want to pass over to the top network is the glue constraint so I'm going to type in Glu e now this actually can be you can name this anything you want this one has to has to be constraint name spelled perfectly no caps and this one could be whatever I want isn't in this case that might actually just make it a capital G glue so we're generating constraints and the constraint that we're passing over is the glue constraint and that's all I need to add in here in the vole annoy fracture now I want to make sure my display flag is still over on the top import because this is these are this is the resulting RBD simulation so if I if I put my display flag here I won't ever see the simulation as a matter of fact if I put my display flight here and i zoom in on this we can see it's actually showing me all of the connected pieces of the constraint network but that's not where I want it it needs to be over here so I see the results of the simulation when it gets passed back over here from the the Dobb network so now i'm going to jump back up to the top level and I'm gonna go into the top Network so on the top Network I'm gonna hit the L key to layout my nodes and then I need to add two nodes here I need a constraint network so I'll right-click and go to constraint the constraint tools oh is it in here than the other one I usually just type it in but let me see if we can find it there it is it's under constraints the constraint network so I'll add that so the constraint network is we we really could probably wire it in a couple places but the the method that sort of mirrors by what would happen if we use the glue shelf tool would be to wire it in down here so after the gravity the first input are objects to be processed which is the RBD network so that goes into the first one and then I'll plug that into the output now I have an error because I have a second required input here which is the constraints to create so that's our glue constraint so I need another node for that so that I can reference it from the geometry Network so I'm going to right click in here again so I'm having trouble right-clicking because of my limited video recording space so now I'm gonna go to constraint tools and I want to create a glue constraint relationship that's the other node what I need in here and then I wire that into that second input and now we see that the error has gone away so there's a couple things I need to do first of all in the glue constraint relationship the data name is what it's looking for so this name needs to be whatever I had named it over in the geometry Network and if we remember I named glue with a capital G but again it could be anything you want you just need to make sure that that name is synchronized between the two nodes then I have to come down to the constraint network node and I have to tell it where to find that constraint so here where it's a soft path I'll click on the Browse button and I'm gonna go to object box object and I want to reference the out constraint null node that we had created over there and I'll hit accept and now actually if we want to double check this I could switch to wireframe mode here wireframe and if I see these the read constraints then I know that everything has been brought in properly now we can control the strength of the glue constraints from the strength parameter right here so it's at the ten thousand so that should let me set changes back from wireframe to smooth shaded that probably will hold most of it together I might get a few chipping pieces and it's a little bit out of frame there let me zoom out a bit let's see it here there we go a couple pieces chipped off so if I lower this value more pieces are going to come off and if I increase that value I could hold it together entirely now the other thing that we did discuss in class two is if we want to animate this you know this is one of the this is the advantage of a glue constraint over the active and inactive methodology for holding parts together in that this whole object can be simulated for doing active and inactive the inactive points are going to stay in place so we can't use that for an object that we want to move around in the simulation so that's where a glue constraint works so I could have this hold together for a few seconds and then maybe after bounces it falls apart we would do that by animating the glue strength here but if you do want to animate the glue strength over time you're going to have to make sure that you also set the default operation from set initial to set always as if we have it as set initial set initial it will only look at the glue strength once at the beginning of the the animation so it won't matter if we animate it it will only see whatever strength was at the beginning if I do set always then it will check that over and over again in order to change the strength so if I want to animate strength I need to make sure I set my default operation to set always and then I should be able to animate the strength value over time and have it the object fall apart so I hope that helps with reference from what we did in class just this past week

Channel: 3dsmaya

Views: 837

Rating: 5 out of 5

Keywords: Houdini, SideFX, Becker College, Lesley University, LA+D, RBD, Voronoi, Glue

Id: PxrrsPKSH8A

Length: 9min 35sec (575 seconds)

Published: Sat Feb 29 2020