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Splines are simply a collection of points that are connected by a mathematical expression of a line. The points that make up that spline can be manipulated to change the shape of the spline. They can also be reordered to change the direction along which data flows. Let's create a very simple B-spline here. I'll switch to the front view by middle-mouse clicking and clicking in the interface here. Let's grab the B-spline tool. I'm just going to click to draw some points. Now, the direction of the spline is indicated by this color here.
White is the starting point and blue is the ending point. The order of the points along the spline is indicated along by the direction. But, how can you see that for real? In the interface here, over on the right-hand side, I'll bring that window down just a bit, is something called the Structure Manager. If I click on that, because I have my spline selected in the Object Manager, it shows me the makeup of the points on that object. And this may look familiar to you; it's simply a spreadsheet. All the objects in CINEMA 4D can be expressed in terms of a spreadsheet.
This spreadsheet tells me the location and space of the points that make up this object, and it also tells me the order of the points. Now, this point that is darkened down here at the bottom is the point that is currently selected. Let's hit the Spacebar to switch back to the Selection tool. If I click on this point, you'll see that it grabs number 6. These points have something called an Index Value associated with them. The first point in this line is always 0. If I grab that, and drag it down in the hierarchy, I've now reordered those points and you can see it's squiggled up my spline.
Let's undo that; Command or Ctrl+Z. If I want to change the order of those points, I can right-click and go to Reverse Sequence, and that will reverse the direction of those splines. You can see now the spline that I had selected is no longer number 0, it's number 7. I can also click on this point, and right-click it, and set it as the first point. That's going to reorder the flow of those points. Now, you can see that my gap, the point at which it would close, is put in a different location.
I'll undo that as well. There are going to be quite a few times where you've drawn a spline, and you want to add points to it. There's a great easy way to do it. I'm going to use the Move tool, hit E on the keyboard, hold down the Ctrl key, and I can click on the spline. That adds a point to that location on the spline. I'll click and add a few extra points here. I'm holding down the Ctrl key, and clicking on that spline. Now, if I hold down the Ctrl key, and click away from the spline, watch what happens. It adds a point to the end of the spline. It added it to that location there.
This point here is part of this curve here, so don't get confused. If I move that around a bit, you can see that it's just from here to here. If I wanted to add a point to this end, I need to reverse the sequence. So, if I right-click, Reverse the Sequence, hold down the Ctrl key, and now I've added a point over there. Now, if I want to close the spline, let's switch back to the Object Manager, grab the spline to get to the spline attributes, I can click the Close icon, and I've closed my spline up. Now, when I reverse the sequence, you see that there is the dividing line where the point begins, and ends.
If I right-click and go to Reverse Sequence, now this becomes the starting point over here. One more thing I want to talk about when it comes to splines is the idea of the intermediate points that will make up a spline. Let's switch to the Perspective View. And the way that CINEMA 4D draws the spline is it's trying to do it in the easiest way possible. That means it's interpreting for you the values between points. So, from this point to this point, from this point to this point, CINEMA 4D is guesstimating what it needs to draw this curve smoothly.
Now, this is expressed in the intermediate points area of the spline properties. The angle defaults to five degrees which usually gives you pretty smooth points. But, if I increase that angle, it's counter-intuitive to what you think. The higher the value, the more jagged, this line is going to become, if I draw that up. Now, because I have a B-spline, you won't see that readily until I deselect it. Now, when I deselect that spline, you can see now my spline is very jagged. When I click on it, it goes back to being smooth. But, this is how it's going to actually operate.
It draws it smooth for you so you can see what the path would look like. If I bring that back to 0, now I get very smooth lines no matter what, and that's the smoothest level. Angle 0 gives you a great adaptive setting. In an earlier movie, I created a Sweep NURBS with a B-Spline. Let's do that again here. I'm going to add a Sweep NURBS to the scene and then I'm going to add a Profile spline and let's do another Star object. Let's make that star really small.
Then, let's take this star and sweep it along this spline. O kay. Now, under the Sweep NURBS, there is a Rotation value. If I twist that around, you'll see that the spline starts to twist. I'm going to crank it way up on purpose. Now, one of the things you'll notice is that the spline, as it twists, first of all at the point where it meets that it is creating a seam there. So let's uncheck on the Path spline. Let's uncheck Close spline. The other thing you'll notice is that it doesn't twist evenly along its length.
That's because of those intermediate points. By using adaptive points, CINEMA 4D is guessing how many points it's going to need, and the less points it needs, the less points it's going to use. And so, that's causing this change in value along the length, it needs more points in this area, so we're getting more twist, and less points in this area, so we're getting less twist. Now, the way to fix that, let's say we wanted to have uniform twists all the way along, let's click on the Intermediate Points pulldown and change it to be Uniform along the length of the spline.
Now, we can increase the number of points. Let's crank that value up. Now, what's happening is because this B- spline does not have the uniform distance between each of the real points, when you spread those points out in a uniform fashion, you still get an uneven distribution. So now, let's go back again. Let's turn the Sweep NURBS off and go back again to Natural, and then increase or decrease that value. You can see that it becomes really hard to get that value to become even.
That's really the point I'm trying to make here. You have to be very careful about how you draw your splines because you can end up with very uneven distributions of points that can be problematic down the road. You can only do so much with the intermediate points, and you'll end up having to redraw or add points to your spline to try and smooth things out.
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