Join Veejay Gahir for an in-depth discussion in this video Blend curves, part of Alias Essential Training.
- I'm going to show you another very powerful command in Alias, especially when you're creating curves, and that's called the blend curve. So let's go up to Curves, Blend Curve Toolbox and this opens up another dialog box and we're ready now to start creating some blend curves. So let's go into our top view, and I'm going to zoom in here like so and for the moment, let's just hide our image plane. So in this case, let's switch to the layer Work in Progress because that's where I'm going to be creating these blend curves. So, let's start with a very simple scenario, this right angle corner, and if I open up the option for Blend Curve Creation, double-click, you'll notice that it's going to create a degree 5 and it's going to default to G2 Continuity.
Let's just go with those, Control and Alt and snap to this curve, I can go to the very end and the same here. And then select Nothing. So you'll notice that the blend curve itself is an associative element, in other words, if I pick these two curves here, this curve turns pink. These are the parents, that's the child, so there's an associativity there. So now if I go ahead and move those two curves, the blend curve will move with it. Like so. So that's first of all, a very powerful part of modeling.
If I model and change these parent curves, the blend curve will try to accommodate that change as well. So, we want to change the shape of this blend curve, we put the blend curve in but it's not exactly what we're looking for. So there are a number of ways we can do this. We can go ahead, pick the blend curve and if I go to CV/Hull, let's switch those on. And now if I pick a CV here and I say move, and we'll try to move it out into the position away from that vertical line, Alias comes back with a warning telling me that if I do this, the construction history will be deleted.
So let's just go ahead and say Yes to this. If I move that now, and if I go ahead and pick the parent curves, this curve no longer turns pinks, so I've lost the associativity. So just be aware of that, if you try to do direct control point manipulation on a blend curve, you will destroy the history. So let's delete that, let's go back in, let's put it in again, like so. Now, again, let's go ahead and move these points, maybe that's not exactly where I want it to put them. So, these are blend points, so we want to pick a blend point and to pick a blend point, we go to the Pick command, Point Types, Blend Point.
And I'm going to pick this blend point and then very simply go to move. I want to use my left mouse button, I want to move it up and down and even if I try to move it left and right, it's locked into that parent curve. So I can do this, I can fine tune these blend points to change the shape accordingly. And at this point, let's just check the associativity and it's still intact, so there's no problem there. Let's go back, pick the Blend Point and we're going to go ahead and move it back to the very top like so.
So let's select this entity, we're going to switch on the CV/Hull and another way to modify the shape of this particular blend point is to use this option here on the CV Tools which is called the Blend Curve Edit Tool. So if I click this one time and pick on one of these end points or the blend point, it comes up with a gizmo. Because we created this blend curve with G2 continuity, we can modify the shape. This square represents tangency and this circle represents the G2 continuity. Now, if I just click on this square and move it, you'll notice that it pushes the tangency control point, which is the very first control point and it moves the second control point which is our curvature control point.
So the tangency will push both. If I click on the circle, I can push just the curvature one. Now, at this point here I might decide that I don't really want to have G2 here, G1 will be fine. So I can go to this icon here and I have a whole selection and I can go to G1 and you'll notice now, all I have left is the square that represents tangency. So let's jump over to this side here. And you'll notice on this side I still have tangency and curvature, so again, I can modify the tangency and I can modify just the curvature.
And I can also change this back to G1 if need be. So let's go back and change them both to G2. And I'm going to click this one here and I'm going to change this one to G2 as well. And, if I hold my Shift down and pick this blend point, and if I now go back to my tangency icon here, I can change both sides of this curve at the same time, like so. So this is another very powerful way to model. So let's go ahead and do that again, I'm going to delete this, very quickly Control Alt, snap those in, put on our CVs and holding my Shift down, I'm going to select this blend point as well and then we can just go to the tangency option and we can proportionally change that blend point like so.
A very powerful way to work. If we pick this blend curve and do a Control-5, let's open up our information window, like I mentioned before, the information window is a really great way to interrogate an entity. But you'll notice that this entity is pretty much locked up, I can't change any of these values and that's because it's an associative element. The only option I have is to change the layer and change the name of that curve. Okay, so let's go ahead and let's just delete this data and we're going to bring back our image plane, make it visible and what I'm going to do here is I want to drop this image plane down a fraction because it is sitting on the same plane as my curves.
So let's go ahead, pick the image plane, and what we are going to do now is we are going to go to the move command, and right mouse button, I want to move it down. But if I do a Control-5, there's information about the image plane as well. And let's look at the Transform Info. Translate in the z was -6 millimeters, let's just make that -5, so it rounds it up. So you can actually specify an exact value in the z direction just by going to the information window.
And at this point, let's just go and make it a reference image. Let's go back to the top and let's take this blend point and use it to try to capture these transitional curves here. So very quickly, I'm just going to go to Blend Point, Control Alt, and I'm just going to go ahead and capture that curve like this, and then we'll do another one here, like so. Select Nothing and then we're going to put one more in here like this. It's like nothing.
So again, we can go back to any one of these curves, I can pick that point there and I can slide this end point as well, I can slide it anywhere along that curve, and what I'm trying to do now is capture that image below. So I can slide, I can change the tangency, I don't have to have the CVs visible for this, but in some cases it's a good idea just to make sure that you're not compressing those CVs inadvertently. So that looks pretty good, select Nothing, now we can pick this one and we can slide this, and we can also go down to this one here and remember we can pick this blend point, shift, pick the other blend point, put on our CVs and using the tangency option, we can change both sides at the same time like this.
So just a very simple exercise to practice putting in blend points and in capturing these transitions.
- 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