Loft Generator Demystified: Loft Generator Parameters

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In this Video, we’ll take a look at a bottle that was made using a Loft Generator and Primitive Circles as inputs, and see how the parameters, affect the Generated Mesh. While doing that, I will explain all the parameters in the simplest way possible.

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Transcript

In this video, we'll take a look at a bottle that was made using a Loft Generator and primitive circles as inputs, and see how the parameters affect the generated mesh. The first thing I'd like you to observe is that the same sequence we have here. So the first circle is circle one, then circle two, three, four, five, and six is represented over here. So you can see the names of each and every one of the circles. The way the Loft Generator generates the mesh is to connect, so to speak, or create a mesh between the first and the second input splines, then the second and a third, third and fourth, fourth and fifth, fifth and sixth. Each and every one of these parts of the mesh are called segments. So first segment is from one to two, second segment from two to three, three to four, four to five, five to six, and so forth. So we have one, two, three, four, five segments. With that in mind, let's go and see the parameters one by one. The Mesh Subdivision U controls how many polygons we're going to have around the U direction. So you can see that the higher this number, the more dense the mesh is around the profile. And this is because the Loft Generator doesn't take into account, the actual spline intermediate point. So if I select circle one, I'm going to go close to this so you can see the subdivisions of the particular circle. If I change the intermediate points of circle one to something like Uniform, and let's increase the number, you will see that regardless of the number of intermediate points, the mesh doesn't change. So as I said before, the burden of creating the mesh subdivision lies on the Loft Generator, not the actual input splines. The input splines just supply a general shape. And the number we use to control these polygons, the number of these polygons is the Mesh Subdivision U. Let me show you something interesting with this. I'm going to set this to five. And what you will see here is that we have four polygons. One, two, three, and four. This is actually one more than the number of polygons. So if you read Mesh Subdivision U and subtract one, that means we're going to get four polygons. If I put this to 31 for example, then I know that if I count these polygons around, they're going to be 30 of them. And of course you're going to ask me why is it? And the reason is that it counts the points and it takes into account that the last point and the first point, which in this case lie on the same position because our circle is closed, is the same point. So if I count the lines here, I'm going to set this again to five. One, two, three, four, five because we want it to close, and that's the reason. So this is the number of polygons or number of points, plus one. So let me set it back to 30. Now let's go to the next parameter, the Mesh Subdivision V. Of course, this is the latitude, longitude, I don't know what I call it, but it's the number of subdivisions that happen in the other direction. So let's make this one and press Enter. You will see that it will set itself to two. Two is the minimum value. And what this two means is that for every segment, we're going to get two polygons. So segment number one, one, two polygons, segment number two, one, two polygons, one, two polygons, and so forth. Now, we use the Mesh Subdivision Value together with the Subdivision per Segment. Because this is on by default, each segment is going to be made out of two polygons, or three polygons, and so forth. If I turn this off, you will see that there are no in-between subdivisions in each segment. And I'm going to raise this to four, nothing happens, five, nothing happens, six, seven, now we got one down here. This number does nothing if it is smaller or equal to the number of splines. Here, we have six splines. So anything from two to six won't do anything. If I increase it above the number of splines, it will start adding segments in the totality of the object. If I make this, for example 13, we're going to have two here, two here, two here, three here, and three here. So it will distribute the extra subdivisions the way it thinks it's best, so that to keep some sort of uniformity in the size of each polygon. So Subdivision per Segment, subdivides each segment by this number. If this is off, it tries to subdivide the whole mesh by this number. And if I start counting, let's make this, for example 10, 1, 2, 3, 4, 5, 6, 7, 8, 9. In this case, when the Subdivision per Segment is off, this is going to be one more than the number of polygons. And again that's for good reason because we may want this geometry to wrap around and come back, and that will create an extra polygon, which is a tenth-one, just like we have with a Mesh Subdivision U and the point. So it's a similar concept. So let me turn this on. Now let's talk about the Organic Form. If I turn this on and off, you can see that nothing really happens. This is mostly necessary when we're using low Mesh Subdivision U numbers. So if I set this to five for example, or let me make it four, and you can see that the size of each row of polygons is slightly different, so these polygons are larger and these polygons are a bit small, and these ones are smaller. But overall, you can see that there's not an equal distribution of the polygons around each circle. If I set this to Organic Form, then the algorithm tries to create equidistant subdivisions. Let me set this back to 30. And let's move to the Linear Interpolation. Now, if I go to the side view, you will see that the transition of the mesh is very smooth, and actually creates a little bulge here. Although I know that this circle and this circle are equal, this is a bit bulgy. And this is because Cinema 4D tries to make a nice smooth transition of the mesh. If I set this to Linear Interpolation, then each segment will be straight, so straight, straight, straight, straight, straight. With this off, it creates a nice smooth transition. The loop, actually loops the last to the first. If I turn it on, you will see that something happened. This, what you see here, is the inner part of the mesh. I'm going to select the top circle. I'm going get my Scale tool and make it bigger, you can see what happens, or I can make it smaller. And basically, if I select the second one, make it bigger, now let's go and see what happens here. We can see a row of polygons going down all the way to the bottom. So this is to create objects that loop around. If I go and turn it off, now you can see we have just the outer shell. If I turn it on, you will see that it loops around. It will be much more visible if I take the second, third, fourth, and fifth, and grow them like this. And now, you will see that we have this sort of shape, which sort of makes sense. Excellent. So this is the loop. Let me change my model back to its original shape. The Adapt UV setting does the following. In order to show it, I'm going to drop this nice checkerboard pattern on my bottle. So this is the default state. If I take the last circle and I drag it down, you will see that the UVs of this segment, because they don't grow, the texture becomes elongated because the same amount of texture needs to cover more height. If I go to the Loft Generator and turn Adapt UV on, then the generator recreates UVs and tries to make each segment have equal distance in the UV space. If you want your mesh to have an overall equal distribution over your model, you click on Adapt UV. If not, you turn it off. Finally, the Flip Normals will just flip the Normals either way. If you don't know what that means, then just leave it as it is. You should now have a very good idea of what the parameters of the Loft Generator do. In the next video, we will talk about the caps and a few other things.
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