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The last stage in NURBS modeling is to set up the surface approximation, which sometimes is referred to as Render Tessellation. So tessellation is slicing and dicing the surface up into triangles. So in order to see this more clearly, I can turn on Edges with the F4 key. And you can see that yes, in fact, it is being sliced and diced up into triangles. 3ds Max is not able to render a NURBS surface directly. So some programs actually have the ability to render NURBS natively, but in 3ds Max, NURBS have to be converted to polygons in order to be rendered.
So that's done through a process called tessellation, and so we end up with a lot of triangles. In the Surface Approximation rollout, you will see that there is a section for Viewports and Renderer. So we can choose Viewports versus Renderer. Now, there is no way to lock these two together. So you'll see that there's a switch here that says Lock. That has nothing to do with the difference between Viewport and Renderer. So this is a bit misleading. This actually has to do with when we adjust these values down here, at the object level, it's going to affect all of the sub-surfaces within here.
If this were unlocked, then we could adjust each one of them separately. But I am going to leave it locked so that we are just making global adjustments to all of the surfaces at once. So you'll see there are some tessellation presets. So I'm looking at the Viewport Settings and if I flip these switches here, I got Low, Medium, and High presets. So High is actually not really that high. But we are just getting an idea of how this is working here. So those presets are kind of useful, but if you want to have more control then you want to adjust some of these values here.
So there're different methods for tessellation. You'll see there's Spatial, there's Curvature, and Spatial and Curvature. These are just different ways to slice and dice, or tessellate this up. So with the Spatial option, we have the ability to set the edge distance. So basically, this is saying, okay, what is the minimum length of an edge? Okay. So if I have a low value here, I can get much shorter edges.
That means a lot more polygons. Set that back up to 5. And Curvature, that gives me the ability to tessellate on basis of an angle. So again, as I reduce these values, Distance and Angle, I'll get more detail. Then you've got the combined Spatial and Curvature. So basically, lower values equal greater level of detail. The other methods here are Regular and Parametric.
We will take a quick look at those. If I choose Regular, what that means is I'm going to get the same number of steps in one of the two dimensions of this object. So we have U and V. So in this case, U is the level of detail running around. So it's the number of meridians, if you will. So these are the lines of longitude. How many of those do you want? Okay, well, a lot: 20, 30. And then, I've got the number of steps going the other direction, which is the number of lines of latitude with a number of parallels.
So I can have fewer parallels. That's pretty straightforward. But you'll notice that since the base surface is locked, in other words, that means that this is affecting all of the surfaces including my extrude, if I get in closer here, you'll see my extrude is really very heavy. It's got more detail than I need. Okay. So that's regular. Then you finally got the Parametric Tessellation method, and you need to be very cautious about this, because if I just clicked this Parametric button right now with a high value to my U or V steps, as you see here, there's a very good chance that I will just crash the program because this is way too high.
Parametric wants to have very, very low values. And if I just, again, just click this now innocently, I could literally crash 3ds Max. So I don't want to take that chance. So I am going to set my U and V steps all the way back down to 2 and 2, and then I'll choose the Parametric method. And you see that's a very, very dense mesh, even with only two steps. So you can imagine, if I had this set to like 30, this would create literally hundreds of thousands of polygons, potentially millions of polygons in this one object, and the program probably wouldn't be able to handle that, and it would just crash.
So Parametric is useful, because it's based upon the number of CVs here. So if I use the Parametric or Regular methods, I can control the level of detail by adding and removing CVs to my curves. I'll actually just go back to the High tessellation preset because that looked okay. And I finally want to mention that if you choose the Renderer option here, unfortunately, you're going to be flying blind completely here. So with the Renderer option enabled, you can change stuff up here all day long, and you'll have no idea what you're doing, because there's no visual feedback in the Viewport.
So you have no clue. So there's really no way for you to link these two together. So what I advise that you do is you use the Viewport method, and then set whatever settings you want for the Renderer and then go to the Renderer and set those values to be the same. I know that that seems a little bit clunky, but that's pretty much what you have to do. With a little bit of practice, you can get good results, because you can dial the viewports down to low level of detail, but yet, in the Renderer, you can have a higher level of detail.
So once again, if I do a quick renderer of this you'll see. The rendering is looking nice and clean, and then the Viewport is kind of chunky and blocky, but it will give me good performance. And that's how we'll set surface approximation to get the best results from a NURBS model.
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