Join Andy Beane for an in-depth discussion in this video Geometry conversion, part of Maya: Advanced Modeling.
- [Instructor] Geometry conversion is not a complicated or difficult task to accomplish anymore, but knowing when to convert geometry types can make your modeling process go much more smoothly. Understanding that NURBS modeling workflows can easily create certain basic shapes that revolve or extrude like wine glasses or chords makes that type of shape much easier to create in the early modeling process, even when you're going to be ending with polygons. Utilizing NURBS tools and converting the NURBS objects to polygon is a great idea and sometimes gets overlooked by new modelers.
And what's even better now, Maya has many of the NURBS Convert tools already built into them. Now you should still know how to convert geometry using the Modify Convert options, because you may receive a model from somewhere or someone else that would need converted for your project. For example, a CAD file for a product design or car design. These would typically come to you as NURBS objects and you would need to make them polygons. Now you can also convert other types of objects like Paint Effects brush, particle, fluids, and textures into geometry which can make some very interesting base models or even finished models.
Paint Effects can generate plants, trees, grass and many more shapes procedurally that you can then convert to a base polygon shape for your project or to finish modeling. Let's look at some of the convert options that you'll use most inside of Maya. I'm starting here in the 02_04 start file, and you'll see that we have a vase that was actually created by revolving a NURBS curve. This is still a NURBS surface. If I right-click on it, you can see I'm still getting control vertices, surface points, holes and isoparms, and I want to convert this into a polygon shape.
To do that, we're going to go to Modify, Convert, and I'm actually going to tear this menu off because we're going to use it over and over again, and the one that we want to use right now is NURBS to Polygons, and I'm going to open up that option box. Now in here, these are the same options that you would actually have in the Revolve tool and the Extrude tool just at the bottom. Now in here we have a few options for creating our polygons, like do we want them to be tris, or triangles, or quads? Either three-sided or four-sided geometry.
Our Tesselation method is set to General, Standard Fit, Count, or Control Points. Honestly I'd never use General or Standard Fit. It's basing the amount of geometry in between isoparms and other NURBS components, that is actually sometimes difficult to get exactly what you're looking for. I will typically either use Count or Control Points. Count is very simple. It is going to give you a certain predetermined amount of polygon geometry that will be used to create the shape from the NURBS surface.
Right now this is set to 5,000. Let's actually set it down to about 200 to start with, and hit Apply. I'm also leaving everything set to Quads to start with. And you'll see that we get a shape built from 200 polygonal faces. Now there might not be enough to really give us the shape that we're looking for, so I'm going to delete that, select our NURBS surface again, and let's up this up to about 8,000 and hit Apply again. And what you'll see are evenly spaced or close to evenly spaced polygonal faces, about 8,000 of them, to create our shape.
Now this would be very useful to able to take into a sculpting program where digital sculpting likes uniform faces across a surface. Now it's a bit overkill, and we probably want to do our conversion if we're going to stay in Maya a little bit more efficiently. I'm going to delete that shape. This time I'm going to choose Control Points, and you'll see there are no options in here for your Control Points, and I'm going to hit Apply. Now what will happen is we will get a slightly chunkier and bigger polygonal version of our NURBS shape, but if I hit the three to show subdivisions, you can see the shapes are identical.
I'll go back to one, and go to our Modeling tool kit, and if I smooth this to two divisions, we will actually get the exact same shape. So the control points will actually give us a lot more efficient ways to convert our NURBS object into our polygonal shape. Let's delete that. Now let's take a look at another example. We have our tail here, which was created with an extrude along a curve, so we used a circle and extruded it along a curve that created this spiral shape.
So again, we can take a look at the two examples that we had before with our NURBS to Polygon conversions. The first will be Count, and let's set this to 200 again and hit Apply. Now in this particular case, this will not be enough geometry for us to really create the shape that we want, and you actually see it's a flat plane wrapped around that particular surface. For a shape this complex, we're going to need about that 8,000 or more polygons to create this rounded shape.
And you can see now we get our nice polygonal distribution of these faces all the way around that particular shape. And again, Control Points here will take the base shape of the NURBS and give us the polygons across that. So again, we'll hit Apply, move this over and kind of take a look at the two shapes beside each other, and you can see the difference, and again, if I hit three, we get almost identical shapes. So that's NURBS conversion. So let's take a look at some other options that we can convert as well.
This is a patch of Paint Effects grass. Now creating this particular shape by hand would be extremely time-consuming, having to create each one of these polygon faces being extruded out to create this randomness of grass, and this is actually just a preset brush inside of Maya to be able to create patches of grass. Now we can't manipulate this particular piece of grass right now as a Paint Effect, so if we right-click on it, there are no components to Paint Effects, so what we want to do is convert this over to polygons.
The other reason you'd want to convert Paint Effects to polygons is for rendering. Maya software is the only thing that can render Paint Effects currently. So we'll come over to our Convert, and we're going to choose Paint Effects to Polygons and open up the dialog box. Now inside of here, I'm going to go to Edit, Reset My Settings so that I get default settings to start with. We have a Poly Limit of 100,000, which means that it will go up to 100,000 polygons for this patch of grass, and really, you can hide the original curve stroke that was used to create the patch, and do we want it to be Quads? I do want it to be Quads, and I'm going to hit Apply.
Doesn't look that much different, and we are now being able to convert and change and manipulate this as polygons because they are. So a really good way to get a complex shape built into geometry that you can then manipulate. Let's take a look at another example. We have a bramble of again, another very complicated shape that we can select, this is another Paint Effects, and hit Apply, and you can see that we now have this shape built through textures for us to use.
We'll hide that and take a look at one more Paint Effects example of trees, and this is a great way to get a tree shape. So again, just select it, we're using the exact same Convert tool, nothing changed there. We'll close that up and take a look. Now there are some mistakes with this, you can see that it will just shove polygon shapes into other polygon shapes and they're not quite connected correctly. But what this will give us, if I isolate just the trunk, is a shape that would actually be very, very difficult to create by hand, which is going to be the trunk of the tree itself, all of the branches, and then all of the limbs.
This would actually take a long time to build and to design from scratch. We will have to go in and clean this up if we were to use it, with how some of these branches are connected to each other, but Paint Effects is a great way to procedurally create these larger organic shapes and then to convert them into polygons. So we're going to hide that. Now two other things that we can convert which is very, very useful are particles, so I have an nParticle layer here, and I'm going to hit Play on my playhead over here to begin to get this streak of smoke going across our scene.
I'm then just going to drag-select our particles and go to our Convert menu and drag down to our nParticled polygons, and there are actually no options for this. So I'm going to click Covert, and you'll see that we get these converted smoke shapes into geometry. Now the nice part about these is the history is still turned on, so if I go back to the first frame, there will be no geometry, and if i hit Play, you can actually see the geometry is animated and growing. Now if you wanted to stop this and be able to continue to keep it, because every time I go back to the first frame I'm going to lose that shape, I can play it to the frame that I want, and go to Edit, Delete by Type, History, and that will actually now keep that particular geometry in that frame, and then we can go in and start manipulating it any way that we want.
I'm going to Undo my way out of that to get my history back turned on, and I do want to show you one thing with these particles and how you could actually affect the shape that you are getting. I'm going to go to the Attribute Editor and look for my particle shape. Within the particle shape, there is an Output Mesh section, and in here are the sliders that we can use for either the Threshold, the Scale, the type of geometry that it's creating, which right now is a triangle mesh, we can change this over to a quad mesh, and this is where you can actually manipulate the resolution, so we can come in and add 600 here, and change our triangle size to a much smaller mesh size, and you can see you get a much more smooth rounded shape.
We can then add the Mesh Smoothing Iterations, and you can get something that looks really, really blobby and kind of smoke effect going across there. So let's hide that and take a look at one more example, which are fluid effects. Now these particular clouds are created with Maya fluids. So again, I'm going to select them, and go to our Fluid to Polygons, and tell it to convert to geometry. So you'll see that we actually get section of sky of clouds, and if we want to manipulate their shape and their geometry, it is also in the Attribute Editor, and we'll go over for the shape here, and it's under my layer shape here, and I'm going to look for the Output Mesh again.
There's a lot of options inside of these fluids and nDynamics, so again just scroll down until we find the Output Mesh, and again, we can change a few things in here to get either more resolution or less. We can change it from triangles to quads, and then you can start manipulating your mesh resolution for what the final effect for this would be. As you can see today, geometry conversion is not difficult, and with a little bit of knowledge, we can get our geometry to look the way that we need and also have it be the type of geometry we need for our final project.
It's also worth looking into fluids, particles and Paint Effects, as they can be very, very fast ways to create shapes that would be difficult to create from scratch, like trees or water surfaces. But having the flexibility to convert the shapes that are generated procedurally, or started with a different geometry type, is an extremely powerful way to build the shapes that you need as a 3D modeler.
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