Join Veejay Gahir for an in-depth discussion in this video Simple fillet, part of Alias Essential Training.
- Let's take a look at creating surface fillets. Now, surface fillets are a very important command in any application, whether it be Isom, Khatir, or Alias. And it is a somewhat complex command, and we're gonna start off with just the basics. And what we'll learn in this tutorial will get you through most scenarios. So, before we get started, we're gonna utilize the Shelves option, so going up to Windows, Shelves. And for those of you who want to customize a shelf in this particular tutorial, I'll show you how to do it and what the value is in doing this. So, because we're gonna be working with fillets, let's go into this blue portion, right-click New Shelf, and let's just call this Fillet.
So, this shelf now is going to contain all the commands that I'm gonna use for creating fillets. So, let's go to Surface. We can right-click and let's open up the options for Surface Fillet. Now, because we're gonna be using Surface Fillets, we can middle-mouse button and drag that into the shelf. Okay, we're gonna start off with Radius at the top. We're gonna use G1 Circular, and you can see we have a whole load of options here for creating fillets. But, we're just gonna do the G1 Circular for now. We're gonna use Center Radius, specify a Radius of 75, and we're gonna use a Form Factor of .5.
And we've covered Form Factor a number of times already. It's quite a common theme now in Alias to use a Form Factor with Center Radius. Flow, leave it on Start and End, Default. And we're gonna keep Auto-update on and Continuity checked as well. So, with this said, let's go ahead, and we'll pick a very simple scenario. So, for the moment, let's hide the Extended. Let's hide Chordal, and let's select Simple Layer. So, let's Select one surface, and we're gonna Select another surface. And we're gonna simply press the space bar to build.
Now, in this case here, I've got Automatic Trim on, and I've got Continuity Check on as well. Now, the only surface is that this particular fillet was allowed to Trim is this pink one at the back here 'cause it extends from edge to the other edge. On the yellow one, it didn't extend all the way, so it can't Trim this surface. And if we take off Trim, this is the result we'd get. Now, you'll notice if you take Trim off, you don't have the option to check your Continuity. So, that's just a point that's worth noting here. So, let's select that Off, and that's just a very simple fillet.
We've created a Center Radius of 25 with a Form Factor of .5, so if we change this to a Form Factor of 1, we will have a true 75 millimeter radius right the way through that fillet. Let's say next to this, and this changes down to .5 again, and let's do the same command. So, we've got two radiuses here: one with 75 with a form factor of .5, one with 75 with a form factor of 1. And let's just very quickly measure those.
So, the measure function is in the Locators, Measure. And let's just drop Radius into here. And while we're at it, let's go ahead and drop Distance as well. Let's click on Radius and then just pick one of these edges here. Once we've selected the edge, we can actually go ahead, pick that Locator and move it. And you'll notice right in the nose of the fillet, we're at 75 millimeters. And then, as we move out towards the Tangent Line, it starts to increase in Radius up to about 192. And that's with a Form Factor of .5.
If I click this one here, you'll notice that we have a Radius of 75 all the way through from one Tangent Line to the other Tangent Line. Let's press "l" to delete. And let's pick those two, and we'll delete them. So, the way a fillet works essentially, is if you can imagine a ball bearing running underneath these two slabs, everywhere that ball touches, these two slabs is what we call a Tangent Line. And that's what we're seeing when we create a fillet. So, let's do the same thing again. Let's double-click. And in this case, we're gonna go back to 75 with a Form Factor of .5.
And I'm just gonna Window over these two surfaces. I don't have to accept. I can just go ahead and Window over these. The arrows are in the right direction for me, and then press space bar to build. Now, let's take off Autotrim. In fact, it's a good idea to keep on Trim for a second, just check that everything looks good, and then switch Autotrim off. I tend to leave the trimming until the very last moments. Now, in this case here, we've got a surface fillet that's created, and we've actually got two pieces here. But, if you notice in the Spans, we've got One Span by a One Span, but we can actually clearly see two surfaces here.
So, if I go ahead and pick one of those, you'll notice that they're actually grouped together, even though it's still coming back saying One Span by One Span. So, if I go ahead and Ungroup that and pick it, there are the two individual surfaces. Let's delete those. Let's go back to Fillet. Space bar to accept. Now, this is an associative entity, so if I go ahead and pick these top surfaces, the fillet will turn pink and the same with the bottom. So, if I do move this data in any way, the fillet will update accordingly.
And again, I can go to Query Edit, so I've set up a hot key, as you can see here "q." Press "q," pick the fillet, and it reinvokes the command. Now, one thing to note here with fillets and in actually any CAD system is if you imagine that ball is running down this theoretical intersection, when it hits a split or an adjacent surface, it will stop there and start a brand new surface I can see here where my cursor is. So, you have to be careful how you split your surfaces up. I'm gonna give you an example of this now.
Let's go ahead and Delete this. And I'm gonna go ahead and create another Split. Let's go Object Edit, Attach, Detach, and let's create a Split right here like that. So, we've got a slight gap between this slab on the side and the slab on the top. So, let's go ahead and Create our Surfaces. Just Window over these top two. Window over the side ones, Accept. Now, you can see what you've got here now. We have a little sliver of a surface on that fillet, and that's not a desirable result. So, ideally, if you have to have a Split in your surfaces, try to make the Split at the same point for both slabs.
And that will help you avoid this kind of situation. Okay, so we can go back to Query Edit, pick that, we can go to Automatic Trim. And in this case, you'll notice that because the fillet extends right the way through for both surfaces, we can do a quick Continuity Check, and let's put on our CvHulls to make sure everything looks fine and it does, except for the sliver in here which we'd wanna avoid. And we're good to go. Let's Undo All. Now, to correct this situation, what we'd have to do, again, is break that surface right at that point.
Let's go to the next Option, which is Chordal, and let's hide our simple solution here. So, with Chordal, let's Shade this model up. You can see in this particular case here, we have a scenario where we have a 90 degree corner at this end of these two surfaces. And as we track down to the back portion, you can see that they're almost aligned at the back. And we're gonna see what kind of result we get here with a fillet. So, let's go back into the Fillet command. Let's open it up, and we're gonna use 75 with a .5.
Let's pick those two, and let's create that surface. So you can see here with 75 and .5, we get a situation where if I just look down the fillet like this, you can see that these two tan lines are starting to converge at the very back here. And that's because these two surfaces are almost aligned at the back portion, and we have a very pronounced 90 degrees here. Now, in some cases, this is fine. And in some cases, it's a situation where you wanna avoid 'cause it doesn't give you very good highlights. So, again, if we change this to 1...
that's the situation we get here. So, we'll go back to .5, and I wanna show you a solution that we can use to correct this. So, let's go ahead, and we'll pick those two surfaces, ctrl + c, ctrl + v to duplicate, and I'm gonna go to the Move command, and I'm just gonna move these out here like that. So, one solution we have is if we open up our Options, we can now go to Chordal. Now, with Chordal, I'm gonna pick my first surface and pick the second surface and accept. Now, the value of Chordal is huge here, so we need to be careful about what value we have, and let's correct that now.
But, you'll notice one thing is that when we switch to Chordal, we don't actually have a Radius value that we can input here. So, what we're gonna do is to switch to Chordal Length, and we have, again, no option to specify a Radius. So, the way Chordal works, it works on a distance, and the distance is what we call a Chordal Length or we have the option for Tangent Length. Let's look at Chordal Length first. So, right now, we've got a value of 212 set here, so what does that exactly mean? So, let's go to our Measure command, Measure Distance, and I want to crl + alt, go to the corner of that tan line and to this one here, so Chordal Distance right now is 212 millimeters between those two tangent lines.
So, let's "l" out of this. So, if I wanted to replicate this kind of look using a Chordal Fillet, I really need to measure what the Chordal Distance is on this particular Radius. Now, remember this is a true Radius, but we need to measure the distance. So, let's go ahead and measure the distance there. So, what I need to do is set a Chordal Distance of 157.7. So, let's move over to here. I can Query Edit, open this up, and change this to 157. So, that is the kind of Chordal Fillet that represents this fillet here, which is a true fillet.
Now, let's go ahead and look at another option. We also have the option to specify a Tangent Length. Now, Tangent Length works on the length between this corner and the first tangent line. So, again, if we wanted to replicate this type of fillet using Tangent Length, what we can do is this, we can measure the distance between this point here and this point here, and it's 111.5. So, let's go back over here, Query Edit. Change to Tangent Length, 111.5.
That's what that fillet would look like with a Tangent Length option. So, let's go ahead. We're gonna open both of these up again, Query Edit, and we're gonna put the Trim command on Automatic Trim. Now, you'll notice that it's not trimming this top surface and that's because this fillet is not extending right to the very edge. And if I zoom into this area here, you'll probably see that right here. So, what we can do is we can set the Default Value for Start. We can set it to Extend, and this one's fine here.
And let's go Next, and I wanna go Query Edit, pick this one again, and we're gonna go to Automatic Trim. And in this case, this one works out just fine. So, now, let's go ahead, Delete the Locators, press "l," and I'm gonna shade this model up. So, you can see the difference between using Chordal and using a regular fillet, is that we have a slight change in the way these highlights tracking across the fillet onto the main slab. And again, this is purely a matter of preference on which gives you the best result, but either one works just fine. Let's go back up, let's change it to Wire Frame, and let's open up our Options again.
Now, in this case here, what we're gonna use is we're gonna go back to our Extended Layer now, and we're gonna hide Chordal. So, with Extended, we have the option... We just opted that in the Chordal option here, but let's go back to Regular Radius. We're gonna use G1 Circular, and we can use Form Factor of .5, and that's just fine. First surface, second surface, and the correct quadrant, space bar to accept. So, we have Default set up right now, and I'm gonna put up my CvHulls here.
And you can see this is what we're looking for, a nice, even distribution of control points along the whole length of that fillet, and that's the ideal situation. Now, we can click on Default, and we can say Extend. And what happens there is that it will Extend to the longest surface out of the two that have been selected. So, in this case, it's this edge here. We can also do the same for this one. Now, here's a rule of thumb that I've used for many years. If I'm using an extension, whether it's on fillets or whether it's purely an extension from the Object Edit Extend command, I try to avoid extending beyond 10% of the overall length.
So, again, it doesn't have to be exactly 10%, you can just eyeball this in. And this is pretty close to 10%, so if I had to extend this any further than this, I would redefine this top surface. Because once you go into Extension mode, Alias has to guess exactly where this area is. There's no real estate there in reality. What it tries to do, it tries to extend this top surface behind the scenes and create this fillet. But, again, it is a little bit of a compromise and sometimes it can cause some huge problems. So, if we click on Extend again now, now we have something called Edge Align, and we can do the same for this one.
But, you can see what's happened here with our control points, our control points now are starting to twist like this, and this is not a good condition for surfacing. So, what we can do here is we need to either break the surface here for the yellow one, or we can extend this top surface to match the corners. So, when you're creating your surfaces in Alias, always try to have your slabs at least matching closely on their adjacent boundaries and try to avoid situations like this if possible. So, because this is an associative entity, what we can do here, very quickly to prove that point, is go to the Extend command, and we're gonna Extend by using Extrapolate, and we're gonna Merge.
Let's go with that, and I'm just gonna eyeball this in. So, just grab the edge, just roughly align it like this, grab this edge here, and then just roughly align it with the top one. And you can see now that the control points are back into a more organized fashion. Let's go back to Query Edit, pick this Fillet. The other option we have here is that we can Modify the Range. So, if I click on Modify Range, you'll notice now if I put this back to Default and Default, I can grab these markers, and I can modify the range like this.
So, there may be a smaller area in here right in the center that my major focus of the design is, and I'm not really worried about these end pieces, but in some cases, because it's extended right out here, the complexity has had to increase. So, just use the portion that you need to like that. Let's pull these back out to the full extent like that, and let's switch off Modify Range. And the last option now is Variable Fillet. So, if I put on Variable Fillet, I'm gonna drop this before I do that to something like 50 millimeters. Click on Variable, and Variable allows me to choose a location along this blue theoretical intersection.
I can just click one time, and then using my left mouse button, I can increase the radius like this, and then Alias will use this as a Variable Fillet, so I can add as many of these as I want to. But, just a point to note here, Variable Fillets can be a little bit dangerous in the respect that you can see the complexity of that fillet has jumped right up to 20 just by adding that one extra fillet in there. So, if I take and add another fillet in here, and let's say maybe I reduce the size like this, and maybe I can go ahead and increase the size like this one on that particular fillet, you can see what's happened, we've jumped up to 71, and this is a very, very, complex surface.
So, Variable Fillet, again, it will give you a result, and for a concept probably will work just fine, and let's go to Extend on this one here. And we'll go to Extend on that one. And if I say Next, let's pick this, switch off the CvHulls. And if we go to a shaded mode, and let's switch off the Model, you can see it actually gives you a very nice concept, but in reality, if we're gonna take that into a Production mode, we would have to do a lot of work to break these surfaces up and simplify them into ideally single Bezier surfaces.
So, just be careful if you're gonna be using Variable. Use it purely at a concept stage to get an idea down quickly, but just note that you will have to go back in later and redefine that surface to simplify it.
- Manipulating views and entities
- Working with layers
- Creating curves
- Sweeping, extruding, revolving, offsetting, and blending surfaces
- Modifying geometry
- Moving, scaling, flipping, and rotating objects
- Trimming curves and surfaces
- Creating copies of objects
- Aligning, combining, and splitting objects
- Analyzing geometry
- Shading models