3D Print a Figure: Making Models Watertight

Photo of Rick Barrett

Instructor Rick Barrett

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  • Duration: 17:22
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  • Made with Release: 16
  • Works with Release: 16 and greater

Areas of a 3D model that aren’t watertight or thick enough may not print properly

Areas of a 3D model that aren’t watertight or thick enough may not print properly. Cinema 4D’s Mesh Checker can help you identify boundary edges, so you can close these holes. You’ll learn how to expand a compound object into separate components using Polygon Groups to Object (Expand Object Groups), use Solo to isolate each part, and close holes with the Polygon Pen tool.



Now that we've gotten rid of all the non-manifold edges that are really nasty, let's go ahead and see how this is gonna slice to see if we've done enough yet to fix this model. So we'll go ahead and export this as an .stl, and I'm gonna call it shotgun again, and replace the original one. And we'll go ahead load this into MakerBot Desktop. We'll go ahead and export the print file so we can see how that's gonna slice. And here in the Print Preview, we'll go ahead and dolly in to take a closer look. And what you'll see here is that we've got a bit of a mess still around the edge of the barrel, as well as over here in the magazine area and the pump area. A lot of these issues come down to scaling, because the mesh here is simply not thick enough for the slicer to properly put the mesh down. And for instance, especially down the center of the barrel, it's not going to be able to print the center of that barrel without support. And the barrel itself is not thick enough to actually be able to print that wall. So, some of these are scaling issues and some of them are still geometric issues due to the boundary edges that we've not yet fixed. So, let's go ahead and clean up those issues, and see if we can get to a point where we can 3D print this. So I'm gonna go back to Cinema 4D and select the shotgun. And you should still have the Mesh Checking turned on. First, let's go in and clean up the barrel. I'm gonna actually just close up the barrel, because having it open here just isn't simply gonna work with my 3D print, especially at the scale that I'm printing. So I'm gonna go into the Polygon Mode, Loop Select with UL, and select this interior loop of polygons that makes up the inside of the barrel. I'm just gonna hit delete to remove those. And then, we've got a hole that we've created. You can tell from the green outline that we've created a boundary edge. So I'm gonna go ahead and close the polygon hole. And we just drag over, it'll show us a preview. As soon as it shows that it's filled that hole, we can go ahead and click. Now, this is created in engon, and ideally I would go in and slice this properly the way I would like it to be cut up. So you'd go into the Knife tool, make sure snapping is on, and snap across here and down here, and, well... I'm just gonna do it anyway. But, the reality is that as long as this is flat, I honestly don't care how the .stl export chooses to triangulate this engon. Because it's just gonna be flat as far as the 3D printer is concerned. But we went ahead and cleaned that up anyway. So, now let's go ahead and jump into the side here. And we've got some interesting stuff going on with the geometry here. One thing that hasn't been made completely clear yet is that we've actually got multiple pieces to this shotgun. And let's take a look at that. We can go ahead and explode this out by choosing Polygon Groups to Objects. And actually, that made a big mess. And the reason why is, we've still got a pose morph tag on here, and so that's recorded states of the points that aren't going to exist anymore once we explode it out. So I'm gonna go ahead and delete that, and now we'll go ahead and choose Polygon Groups to Objects. And this top one is still the entire shotgun. We'll go ahead and just grab the pieces on the bottom here and move them out of the hierarchy, and I'll delete the top shotgun. And now what I think I'm gonna do is go ahead and switch the Solo Mode to Viewport Solo Single, and also Viewport Solo Selection, which will make the Solo actually follow what I have selected. So I select the first piece here; you can see that that's the trigger guard, so I'll just type guard. And this part's the barrel, the sight, the pump, the stock. I'm not sure what this part is, but I don't think it's gonna be necessary, so I'm just gonna delete it. And this is the trigger. All right, so now let's take a closer look at each of these pieces. If we take just the barrel, there is this piece that goes down the length of the barrel, and you can see that there's some sort of an issue with it, because we've got boundary edges on it. So, let's go into Loop Selection and I'm just gonna select a loop here and I'm gonna select a loop here, too, so that we get that boundary edge. And let's come around to this side, and we'll select this loop as well. And let's go ahead and choose Select, Hide Unselected, so we can see what we've got. Now, what we have here is sort of this weird U-shaped channel that's modeled into this, that's actually not really connected to anything else. You can see that the green line goes all the way around it to show that it has a boundary edge, all the way around at least this front part of it, and then the back part is a little bit different. But we'll go ahead and delete all of these polygons. Now, if we go ahead and Unhide All, you can see that we took care of that weird geometry that was floating around in there. You're gonna come back here to the back portion, and you can see there's still part of that U-channel right here, so we'll go ahead and select that and delete it, and that got rid of that boundary edge. And this boundary edge down here, we're actually gonna have to model around to clean up. So first of all, I'm gonna delete these two pieces right here, because I don't need those. And next thing, you wanna go ahead and go into Edge Mode and select these two edges. And we'll just go ahead and extrude those upward. So, I'm gonna go into the Extrude tool and I wanna go ahead and drag to extrude, and I wanna extrude them up. And because my scale is so small, I'm actually gonna need to go ahead and tweak my extrusion amount numerically in the Attribute Manager. That looks pretty good. . .somewhere in there. Make sure that the edge angle is negative 90 degrees so that the extrusion is going straight up. You see that as I shift this around, it's either extruding back, or over. We want it going straight up so that it'll line up with these other edges that we've got here. Next, we'll go ahead and go into the Polygon Pen tool and I can make sure Auto Weld is on and just drag to weld those points in with the surrounding points. Now, to close this top hole I can just go ahead and, still in the Polygon Pen tool, take this edge and extrude it by holding down the CTRL key. And Auto Weld should actually have that automatically snap in to the surrounding edges. You might have to fiddle with your mouse a little bit to get it to snap, but once you get to the right spot, you should see it snap all the way around. We'll go ahead and hold down the CTRL key and grab the opposite edge and do the same thing, and once again, it snaps in closed. Let's loop around here to the back of the barrel, and you can see that we have some open edges here as well. So, let's go ahead and just close those up. We'll go ahead and choose Close Polygon Hole again and close those two holes up. So now we have a barrel that I believe is completely solid without any geometry issues. We'll go ahead and go into the Mesh Checker, and yes, you can see that indeed there are no boundary edges and no non-manifold edges, so this is a completely solid barrel. We'll go ahead and jump into the pump now, and you can see that we have a boundary edge here as well, because the inside of the pump was not modeled. For game modeling, it's certainly not necessary to model those polygons that won't be seen. You're always trying to save the polygons, but here we wanna go ahead and make this into a solid object. So, I'm gonna go ahead and go back into Polygon Mode again, use my Loop Selection tool, UL, and we'll select this loop right around the edge of that boundary edge. And we'll go ahead and move around here to the other side, and we'll select this loop of polygons that includes the boundary edge as well, holding down the Shift key. Now we're gonna go ahead and go to Select, Hide Unselected, and we can see just those two loops. And we can use the Bridge tool to connect these. So I'm gonna go ahead and choose Bridge. And you wanna make sure that Delete Original Polygons is disabled so that these polygons that we have here selected will stick around once we've done the Bridge. And we'll just drag from one side of the Bridge to the other. You wanna just try and make sure that you're dragging from the same edge to the same edge so that the Bridge doesn't twist. And now we can see that we've closed that up. The normals are not lined up. You can see that the edges here have the normals aligned properly and the inside does not. We'll just go ahead and choose Align Normals, and that got it all lined up properly. Now we can go ahead and Unhide All, and we've got a completed pump, which, if we go into the Mesh Checker, has no non-manifold or boundary edges. We'll go ahead and go to the trigger guard and check it out. It's fine. The trigger has some boundary edges, so let's go ahead and just close that off. Not sure if it'll matter or not, but it can't hurt. Here, we can very simply just go in and just Close Polygon Hole and select in here, and that'll take care of that. And the stock, I believe, is fine. So now we'll select all of these again and Frame Selected. And it looks like we do still have some boundary edges on the sight, so we'll go ahead and once again close the polygon hole there. And now we'll go ahead and Frame Selected again. And I think we've closed all of our holes and have each individual piece watertight. Now, ideally, what we would do is go ahead and actually model all of these objects together using Booleans, or in this case, we're probably going to have to actually polygonally model them into one object. But in lieu of making this a completely intensive modeling tutorial, let's see if we've gone far enough to get our shotgun to print properly. I do wanna go ahead and add in some more smoothing again, so we need to go ahead and add a subdivision surface object. Now, if I drop all of these objects straight into the subdivision surface, it doesn't do anything-- let me go ahead and turn off Solo-- because the subdivision surface only affects the object directly underneath it. So if I go ahead and group all of those objects, now we get smoothing on all of them. But, you can see that the barrel actually gets a little too smooth, and to solve that we'll use HyberNURBS weighting. Weighting actually allows us to take certain edges, and I'm gonna go into Edge Mode and select the barrel, and we'll go into Loop Selection, UL, and we wanna select these vertical edges. And the HyperNURBS weighting is going to allow us to take these edges and make them sharp simply by dragging the weighting. So, with these selected, I'm gonna hold down period and drag, and you'll see how those areas sharpen up. It keeps the smoothness on the round edge, or the round profile, but sharpens up these edges that need to be sharp. So, we'll go ahead and select a few more of these vertical edges. And we're gonna go ahead and hold down period and drag there, and I think that pretty much does it. It looks like we have one more edge here, it's kind of tricky to grab, and we'll go ahead and weight that up. So now, we have nice, sharp edges around this profile, but around the circular profile, it's nice and smooth. We can also do something like select the sight here, and go into the Live Selection mode, and we're gonna just go ahead and select all of the polygons of the sight, go into the subdivision surface tab. And I wanna go ahead and set the strength here to 50% and hit Set. And that just sharpens up the entire sight so that that whole portion of the model is a little bit sharper, and yet still smooth. And I think we need to do the same thing with the trigger. We'll go ahead and select the trigger here, Select All, and go into the Live Selection, and again, set it to 50%. And in fact, with the trigger itself, I think this is gonna be really skinny for the 3D printer to print, so let's just scale the entire object up a little bit, and maybe even have it sort of connect up with the guard. And let's take that guard as well, and we'll go ahead and take those edges and sharpen them. And it looks like this outside could stand to be sharpened as well. So again, we're just Loop Selecting, and then holding down period, and dragging. All right, so now let's go ahead and export this and see how the slicer does with it. So I'm gonna go ahead and export as an .stl, and call it shotgun again. We'll return to MakerBot Desktop, and I'm gonna delete the shotgun we have here, add it back in. I wanna take scale out of the equation here and just see if the geometry itself looks good, so I'm just gonna go ahead and choose Maximum Size for the size of this object, and we'll go ahead and export the print file and see what we've got. Now, if we look at the Print Preview, take a look at this, and it looks like we've got really nice, clean printing if we don't account for the scale of the shotgun. So, it looks like the MakerBot is happy now with the geometry itself. We may have to make some further adjustments due to the size of the shotgun, but I think we're in pretty good shape to move on here. So let's go ahead and return back to Cinema 4D. We'll rename this shotgun. And I'm gonna to take this entire shotgun model and copy it back into my farmer scene. We'll just delete the shotgun we have here, and paste the new one, put it underneath the subdivision surface, and zero out the coordinates. Now we'll go ahead and dolly out, turn off our Solo, and it looks like we're in good shape.
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