Join Veejay Gahir for an in-depth discussion in this video Aligning curves, part of Alias Essential Training.
- In this video, we're going to take a look at a very important principle of Class A surfacing and that's going to be the Align command. Whether we're using courtier or isomer alias, this is a very important principle to understand to achieve good quality surfaces. In this case, we have a very simple scenario, and the principles that we're gonna use here will be applied directly to more complex surface lines. So, the Align command is under Object, Edit, Align. And we're going to start off with a reset and just do a G0 edge align, and we're gonna pick our first curve.
Now, it doesn't matter where you pick it, we can pick it here, and this is gonna be the curve that's gonna move, and then we can pick this curve over here, so we can pick the curve in the middle like that. It's gonna snap to the end, but we can drag this point using the marker. This end is attached now to this curve, so I can't pull this end away from that curve, we have a G0 align. Let's revert that, and let's move over to G1, so exactly the same, we'll pick this curve, and then this curve, and now you'll notice that we've moved the first control point to achieve G0, and we also moved the second point to imply tangency here.
Now the rule here is that this control point, this control point, and this control point have to lie on an exact straight line to achieve G1, and that's the same for surfaces. So if I pick this CV, and I move this, and this is the master CV, so I can drive the other one by moving this, you'll notice the other one follows, and between this CV here and this CV here is exactly a straight line. Let's just move that line out of the way there, that was just for reference.
Now, to reinvoke the line command, just press on Query Edit, Q, and that's going to reinvoke the command. So, at the same time, I can move to G2, and you can see with G2 now, it grabs the third control point, Now, I can slide this one, I can slide this control point, and I can also slide the very end control point. So, I'm adding more and more control points as I'm increasing the continuity here. And the G3, we're actually taking in account the fourth control point as well, that's how we add continuity from G0 to G3.
Now, with blending, if I click on Blending, blending is a really useful function, because you can see I'm isolating the change to this control point and this one, this one, and the very end. But this control point down here is not having any influence over the curve, so I could actually end up changing this curve like so, and we could have an undesirable condition because this last control point has nothing to do with this particular align. But if I click on Blending, and I add one more row like this, what it does is pull this control point into this algorithm, so now I have a really nice, smooth transition ride the way through to the very end.
This is a very useful function to try to have a nice transition from one end to the other. Let's take that off for now, and we're gonna revert back to this condition. So let's have a look at this condition here, where one curve sits underneath the master curve. So we're gonna go back to G0, pick this curve, and it doesn't matter where I pick on this curve, even if I pick in the middle, you'll notice that the projection is normal to that curve, and I can then drag this curve to any location that I want to. There is an indicator telling me where the normal projection was, like that, and I can actually snap to it if I need to.
Same time, I can add G1, and I can drag, I can add G2 and I can add G3, and in this case, you can see the value of blend, because right now we have a very flat condition at the back of this curve, if I put on Blend, add one more, you can see that transition is really quite nice now, back in the rear portion of that curve. So let's do a revert, the Edge and Project, we're gonna look at those in more detail when we look at surfaces, but because we're talking about curves here, let's do one thing, we're gonna take these now out of 2D mode, so let's grab these two, let's go back into the Move command, and using my right mouse button, I'm just gonna move them in the zed location, and in this case, I'm just gonna make this one invisible.
Let's go ahead and do the align again, and now these are not on the same plane. In this mode here, let's go back to Object, Edit, Align, let's do a quick reset, first point, second point, again I can drag wherever I want to, and we'll just rotate it like this so we can see these a little bit clearer, maybe we'll just take the grid off as well. Let's increase that to G1, and remember the rule for G1 is that this control point, this one and this one all have to be on exactly the same line, which they are.
Query Edit, let's reinvoke the command, and go to G2 and then we can go to G3. Now in this case here, if I go into the Right view, you can see that what's happening here is that I've got a condition where I've got a nice, smooth transition from there, then I've got this kind of undulating curve or what we call an inflection. This is not a great condition, but again, if we click on Blending, and add that extra CV at the end into the equation, you can see now we have a really nice, smooth transition all the way through. Again, that's the value of using the Blend command.
At any time now, I can take any of these and just adjust them, but now because I have G3 implied here, if I move the tangency, the other two will now move accordingly to try to maintain G3 at the same time. Take a look at some of the options down at the bottom here. We can have a Proxy Display, so we can see where the curve move from and where it's moved to, and we can have Diagnostic Feedback. So if I move this, see at the very top there, we can see the tangent scale in fact is changing, and also the tangent scale factor here is changing.
But again, let's just keep it very simple, and we're gonna use these options here. Let's go into the next layer here which is Curve to Surface. We've been looking at just curves right now, but we can actually match a curve to a surface, so if we rotate this around, and let's take a look at what we have here. Again, a very simple surface here, if I shade that up, we can actually match these curves to the internal portion of a surface as well as to an edge. Right now, this surface has patch precision lines, so if I press P for Patch Precision, move to the left, these's no isoparms visible right now, it's actually a single span, or a Bézier surface, or I can actually add patch precision lines by using Object, Edit, Patch Precision.
So let's go back to the Align command, let's do a reset, and we can pick this curve, and then we can pick one of these isoparm lines, we can pick this one here like that, and you'll notice the projection in this case, again, is normal, so I can grab this line and I can move it like so, and I can also add G1 onto there, and again, I can go through the whole methodology of going all the way through to G3 and adding a blend on as well. Again, now if I move this, it's always going to be matched to that isoparm.
So if I get to a condition like that, that I'm happy with, I can then go back to this patch precision line, take it back down to zero, but that curve is still internally aligned to its surface. The other thing I can do is I can actually match to an edge of a surface, so let's go back to Align, let's do a reset, let's pick the curve, and we'll pick the edge like that. You'll notice it projects it normal to that edge, I can add that tangency, and I can add G2 as well. At this point here, I can also drag, but you'll notice there's an indicator that shows me where the point for the normal projection resides.
- 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