Refining Polygons


When you're modeling low-poly objects, the basic polygon tools are sufficient. However, adding faces and controlling the number of faces required to get a smooth piece of geometry can be prohibitively difficult. Maya provides options to smooth your surfaces so you don't have to do it by hand.

Polygons start with sharp edges and corners. You can round them by using the Polygons > Smooth function, which subdivides surfaces into many smaller polygons to round their corners and edges.

To smooth a polygon:

1.

Create a cylinder primitive, and set the options as shown ( Figure 8.102 ).

Figure 8.102. Create a poly cylinder like this one.


2.

Choose Polygons > Smooth.

The Polygon Smooth Options dialog box opens ( Figure 8.103 ). A higher Subdivision Levels value in the Polygon Smooth Options dialog box creates a smoother object with more faces. The Continuity setting determines how closely the new shape resembles the original (versus how rounded it is). A low Continuity setting makes the object appear more similar to the original shape; a high Continuity setting produces a very rounded shape.

Figure 8.103. The Polygon Smooth Options dialog box.


3.

Adjust the Subdivision Levels slider to set it to 3.

4.

Click Smooth.

The object becomes smooth ( Figure 8.104 ).

Figure 8.104. The new cylinder is much smoother and also much denser.


Tips

  • The basic structure of a polygon object should be complete before you apply the Smooth function. Smoothing produces a dense object with many faces, making it more difficult to work with.

  • You can set Subdivision Levels in the Polygon Smooth Options dialog box as high as 4; however, 3 is generally high enough (and a higher value can give you a cumbersome surface due to an abundance of point information).

  • You can change the level of smoothing after the function is complete by clicking polySmoothFace1, which should be at the top of the list of inputs in your Channel Box. You'll see a field labeled Divisions, which you can change from 0 (no smoothing) to 4 (very smooth) ( Figure 8.105 ).

    Figure 8.105. The inputs in the Channel Box let you change the Smooth options after the function has been run. However, once you make additional tweaks to the surface, going back and changing the options in the polySmoothFace input field will produce undesirable results.

  • You can smooth a portion of a polygon surface by selecting the faces of the part of the surface you want smoothed and then applying the Smooth operation ( Figure 8.106 ).

    Figure 8.106. (Left) The faces on the top and bottom of the object have been selected. (Right) The result of the Smooth function, which works by selecting whole polygon objects or faces of the object.


Smooth proxies

The Smooth Proxy tool is ideal for situations when you want to work on a low-res model but still want to see how the model will look when it's smoothed or converted to a subdivison surface. With the addition of the Poly Crease, Split Edge Ring, and Duplicate Edge Loop tools, the Smooth Proxy function has become an even more powerful option for poly modeling. Poly Crease lets you add detail without adding more faces, whereas Split Edge Ring and Duplicate Edge Loop let you quickly stitch in geometry where you most often need to define your smooth mesh.

Using the Smooth Proxy tool, you can preview a smoothed version of your low-res model (just as if you had applied the Smooth command to it). The original lowres surface remains visible, allowing you to manipulate fewer points while still viewing the final smoothed shape.

The low-res and high-res surfaces are linked; edits to the low-res mesh are reflected in the hi-res mesh, but not vice versa. For this reason, you should avoid adjusting the hi-res mesh until you're certain you don't need the low-res mesh, or you may have unwanted results.

To facilitate poly modeling using the Smooth Proxy tool:

1.

Select a polygonal object in object modein this case, the base cylinder from the previous task.

2.

Choose Polygons > Smooth Proxy, and set the Subdivisions Level value to 3.

3.

Click Smooth.

Maya creates a new, smooth version of the model while also retaining the original ( Figure 8.107 ).

Figure 8.107. Smooth Proxy lets you view a smooth version of your model while you work on a lower-res version. The original cylinder is displayed as transparent cage, and the smoothed cylinder rests in the center.


Because you set Subdivisions Level to 3, the smooth version looks the same as if you'd performed Poly Smooth on it.

4.

Right-click the original object, and select Vertex from the marking menu.

5.

Select and move one or more of the vertices.

The hi-res version of the model mirrors the manipulations of the low-res model ( Figure 8.108 ).

Figure 8.108. A smooth proxy provides a low-res control cage to control many hi-res points. This allows for easy and smooth adjustments to dense surfaces.


Tips

  • You can quickly define a smooth proxy for an object by pressing . The same command can be used to turn the proxy off again.

  • You can also toggle the display back and forth by pressing the key. To show both displays simultaneously, press .

  • Only adjust the low-res, or unsmoothed surface. Adjusting points on the smooth (high-res) mesh will cause problems if you later add or remove faces on the low-res mesh ( Figure 8.109 ).

    Figure 8.109. The high-res points on this model were adjusted, and then a low-res face was subdivided. As you can see, the results are messy.

  • Select the Proxy or Smooth Mesh In Layer check box in the tool options to place the new objects on separate layers. Doing so lets you hide all your low-res objects, to easily ensure they don't render. It also ensures you don't accidentally modify your hi-res mesh.


In some cases, you'll want to smooth your poly model but keep certain edges sharp. Smoothing a circular glass tabletop, for instance, results in a lozenge shape. In previous versions of Maya, you could only retain your sharp edges by duplicating them, which could be tedious and costly in terms of face density. To avoid adding extra geometry, Maya now lets you crease poly edges, which makes them sharper and pulls the object towards them.

To crease a polygonal edge:

1.

Choose Create > Polygon Primitives > Cube.

2.

Choose Polygon > Smooth Proxy ( Figure 8.110 ).

Figure 8.110. A smooth version of a cube looks like a sphere. You'll crease its edges to change that.


3.

Choose Polygon > Poly Crease Tool.

The object is automatically brought into edge mode.

4.

Select the bottom edges of the cube. With the middle mouse button, drag to the right.

The edges become sharper, drawing the smooth version of the model down toward the corners. Because the side edges aren't creased, the object remains round on the sides (Figure 8.111).

Figure 8.111. Creasing the bottom edge draws the object toward the corner, which makes it sharper and sharper.


5.

Repeat step 4 for the top edges ( Figure 8.112 ).

Figure 8.112. With both top and bottom creased, the sphere has turned into a cylinder.


6.

Select the top and bottom edges, and scale them down until the cylinder looks like a tabletop (Figure 8.113).

Figure 8.113. This circular disk is defined by only six control surfaces, making it easy to adjust.


Tips

  • Dragging to the left lessens the amount of creasing. Even an edge that has no influence remains highlighted if you have creased it previously.

  • The Poly Crease tool can create easy bevels on an object. Crease the edges until they're as sharp or round as you want.

  • By adjusting different edges different amounts, you can use the Poly Crease tool to blend between a sharp corner and a rounded objectsomething that is difficult with polygons ( Figure 8.114 ).

    Figure 8.114. Creasing makes this otherwise awkward object easy to form with poly modeling.


Reducing the poly count

The Polygons > Reduce command reduces the number of faces in a selected mesh or subset of a mesh by a user-defined percentage. Keeping the polygon count as low as possible is important in games and interactive media to keep rendering time to a minimum. The Reduce tool can help you achieve this.

To reduce the number of faces in a polygonal mesh:

1.

Select the polygon object or the set of faces you want to take polygons away from ( Figure 8.115).

Figure 8.115. A poly object with too many polygons.


2.

Choose Polygons > Reduce.

The Polygon Reduce Options dialog box opens.

Modeling for Proxies

Smooth Proxy is a powerful tool because it lets you make a smooth surface, retain high-end control over that surface, and still enjoy the freedom and responsiveness of poly modeling.

If you want to use Poly Smooth or a smooth proxy to make your model, it's a good idea to do some advance planning. Keep these points in mind while you're working:

  • Smoothing your model almost always makes it smaller in volume, so the low-res mesh may sometimes need to overlap. The closer the edges are, the closer the smoothed geometry will be. Plan big.

  • Edges that are close together will form harder edges in your smoothed model. Use the Duplicate Edge Loop tool to add edges near each other.

  • Check your smooth version often if you don't have it displayed.

  • Fairly low-res geometry can form very smooth surfaces (a cube turns into a sphere, for instance), so don't add more detail than you need to your low-res mesh. Start low, and go up if you need to.

  • If something is smoothing strangely, ensure there are no n-gons in your control mesh, or add more geometry to your control mesh so you can better manage that area.

  • Remember that the Poly Crease tool can sharpen edges. Keep in mind which edges you plan to adjust and which you plan to keep smooth as you work on your low-res mesh.

  • Don't put too much stock in how the low-res object looks. In many cases, the low-res object won't closely resemble your goal object. It's the smooth version people will see.


3.

Set the Reduce by (%) field to the percentage of polygons by which you want to reduce the mesh80%, for example ( Figure 8.116 ).

Figure 8.116. Set Reduce by (%) to the desired percentage of reduction; here, 80% is used.


4.

Click Reduce.

The polygonal mesh is reduced to 20% of the original number of polygons ( Figure 8.117 ).

Figure 8.117. The poly object now has 80% fewer polygons than before the reduction.


Tips

  • To keep a copy of the original, higher-res surface, select Keep Original in the Polygon Reduce Options dialog box.

  • Reducing your mesh too much can result in ugly geometry. If you need to cut a lot of faces out of a model, concentrate on reducing in the less important areas, so you can preserve detail where it counts.




Maya 7 for Windows and Macintosh(c) Visual Quickstart Guide
Maya 7 for Windows & Macintosh
ISBN: 0321348990
EAN: 2147483647
Year: 2006
Pages: 185

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