Join Veejay Gahir for an in-depth discussion in this video Trimming surfaces, part of Alias Essential Training.
- In this video we're gonna trim some surfaces. Now, one thing to note here is that trimming a surface in Alias is the same as facing a surface in ICEM or Catia, it's just a difference in terminology. So when we trim a surface in Alias, we can always go back and retrieve the original data. So that's a very important point to note here. So let's go ahead and trim this surface. So we'll open up Surface Edit, Trim, Trim Surface, and we're just gonna go ahead, pick this surface here. Now this surface has a curve on surface already projected on there from this ellipse that's been templated.
So I can very simply now just select a region of that surface that I want to keep. I can move this marker over here. I can move this marker to here, and then I can just simply press Keep, or I can Revert, or I can press the space bar to execute the command as well. So let's Revert. Let's move this to the middle, space bar to keep, and Revert. Now, the only other option that I go down to the bottom right hand corner down here is to Divide. And if I Divide, you can see that I actually have two distinct entities now, this one and this one.
So let's take this and delete it, and as I mentioned before, we can go back to Untrim, and we can untrim all and retrieve the original data. So this is essentially a face command. Let's go to 3D Trimming, and, in this case, let's shade this up, and we're gonna go straight into the 3D Trim command. With 3D trimming, we get the option to select a vector to project. So we're gonna 3D Trim, Project in the Zed vector, select the surface, and, in this case, I'm gonna select that ellipse again, and you can see the advantage of doing 3D trimming is that we can create the curves on surface during the trim command, so it saves us a step.
Prior to this, in the previous example, we had to project the curves on surface and then we went to a trim command. So this is all now rolled into the trim command itself, and again, very simply pick the side that you want to make sure you're on keep, and select that side. Let's Revert this, and we're gonna go back to the command, and we'll pick the surface, and we're gonna pick the letter A. Again, let's make sure that History is On, and in this case, I'm gonna go ahead and pick this outside portion and also the inner portion here.
So there's the trim. Now if we select the A and we say move, you'll notice that the trim will move with it. Now, we've got a problem here because what happened when I was moving that is that the A just crept off the edge, and as I move back, it can sometimes untrim as you see here. So there's a potential problem if you do end up moving the data and it falls off the edge of the surface. So let's go back to Trim, Untrim, and then when it untrims it leaves a curve on surface, and we can just go ahead and delete those like that.
So let's go back to the Project command, in the Zed vector. Surface, and then also this curve. Now you'll notice that we have a potential problem here with these red markers. Alias is warning us that the projected curve is not quite reaching the edge, and this trim is not gonna work. So if I try to pick this edge here, and I say Keep, it just doesn't work. So let's Revert that. One option that we have here is to click on Extend, and we have a tolerance that we can play with. So if we increase the tolerance to, let's say, five, and again, I'm gonna make sure that History is On.
Let's click this portion here, press space bar. Now Alias comes back with a warning saying that "Trim Failed. "Attempting to extend curves on surface "will require construction history to be removed." Essentially what it's telling us here is that because it's had to do an extension, it can't maintain history as well, and that's fine. We're gonna click Yes to this, and it still failed. So let's go ahead. Try it one more time. And with the extension, I'm gonna right up to ten millimeters, click on this side, let's say Yes to that, and ten millimeters works just fine for us.
Let's go to the final mode and that's Intersect. Let's take a look at these two surfaces first. Let's shade this up, and again, you can see that one surface is just slightly smaller than the other surface, so let's see what potential problems that's gonna give us. 3D Trimming and we're gonna switch to Intersect this time. So with Intersect, let's pick the top surface and then the bottom surface, and now we have green markers at the end, so this should work just fine. Pick the location, space bar to accept, and let's Revert this.
Let's go back to the command, and we're gonna pick the lower surface and then the upper surface, and again, the same warning that we have right now is that we have these markers appearing. So let's click on Extend, we can go right up to ten millimeters, pick this portion here, space bar. We get the same warning because we're asking it to try to keep history. And there's the end result. I'm just gonna delete those, and let's move over to these two spheres. Now this is a potential problem in any CAD system. We have two periodic entities, and they're intersecting, and we're gonna try to trim these.
Ideally we want to really split these into four pieces or at least into two pieces, but let's see what we can do here. So let's go to our Trim command, and this time I'm gonna remove construction history. We're gonna go to Intersect and let's take off Extend. Let's pick this first surface, and then this second surface, and we have the intersect. Pick the portion that we want to keep, and Keep. So now if we go to our shaded mode, let's select this, and we'll move. You'll see that we have a hole in that entity, like so.
Control z to bring it back, and now I'm gonna basically divide this blue surface along that open edge. So let's go to Wire Frame, open up Trim again, and this time we're gonna go with Project, and we're gonna go with Normal. Now Intersect would probably work, but this edge is sitting right on top of this surface, so the safe bet here is to use a Project command. So let's select the surface, let's make sure that history is not on, let's select this surface, and we're gonna project this edge, and we're gonna project this edge here.
Now, here's one of the potential problems with a periodic entity is that the projection is not only projecting onto this front face, it's actually going back and projecting onto this rear face as well. So let's pick a portion and this time, I want to say Divide. Now, we've got some remnants of the curve on surface back here, and we can just very simply go into Curve on Surface window, and Delete. Let's go ahead and pick this entity here, and we're gonna move it, and let's go to a quick Shade.
Like so, and this is the remnants of what we have. So this is how we can use the 3D Trim with Intersect and Project to create some quite interesting shapes.
- 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