Edit Geometry Modifiers


Most of the Mesh Editing modifiers are used to change the geometry of objects. Some of these modifiers, such as Extrude and Tessellate, perform the same operation as buttons available for the Editable Mesh or Editable Poly objects. Applying them as modifiers separates the operation from the base geometry.

CROSS-REF 

You can find a more general explanation of modifiers in Chapter 12, "Introducing Modifiers and Using the Modifier Stack."

Cap Holes modifier

The Cap Holes modifier patches any holes found in a geometry object. Sometimes when objects are imported, they are missing faces. This modifier can detect and eliminate these holes by creating a face along open edges.

For example, if a spline is extruded and you don't specify Caps, then the extruded spline has holes at its end. The Cap Holes modifier detects these holes and creates a Cap. Cap Holes parameters include Smooth New Faces, Smooth with Old Faces, and Triangulate Cap. Smooth with Old Faces applies the same smoothing group as that used on the bordering faces.

Delete Mesh modifier

You can use the Delete Mesh modifier to delete mesh subobjects. Subobjects that you can delete include Vertices, Edges, Faces, and Objects. The nice part about the Delete Mesh modifier is that it remains in the Modifier Stack and can be removed to reinstate the deleted subobjects.

The Delete Mesh modifier deletes the current selection as defined by the Mesh Select (or Poly Select) modifier. It can be used to delete a selection of Vertices, Edges, Faces, Polygons, or even the entire mesh if no subobject selection exists. The Delete Mesh modifier has no parameters.

Note 

Even if the entire mesh is deleted using the Delete Mesh modifier, the object still remains. To completely delete an object, use the Delete key.

Extrude modifier

The Extrude modifier can be applied only to spline or shape objects, but the resulting extrusion can be a Patch, Mesh, or NURBS object. This modifier copies the spline, moves it a given distance, and connects the two splines to form a 3D shape. Parameters for this modifier include an Amount value, which is the distance to extrude, and the number of segments to use to define the height. The Capping options let you select a Start Cap and/or an End Cap using either a Morph or Grid option. The Morph option divides the caps into long, thin polygons suitable for morph targets, and the Grid option divides the caps into a tight grid of polygons suitable for deformation operations. The Cap fills the spline area and can be made as a Patch, Mesh, or NURBS object. Only closed splines that are extruded can be capped. You can also have mapping coordinates and Material IDs generated automatically. The Smooth option smoothes the extrusion.

CROSS-REF 

Chapter 14, "Drawing and Editing 2D Splines and Shapes," includes a good example of the Extrude modifier.

Face Extrude modifier

The Face Extrude modifier extrudes the selected faces in the same direction as their normals. Face Extrude parameters include Amount and Scale values and an option to Extrude From Center. Figure 16.7 shows a mesh object with several extruded faces. The Mesh Select modifier was used to select the faces, and the extrude Amount was set to 30.

image from book
Figure 16.7: Extruded faces are moved in the direction of the face normal

Tutorial: Extruding a bullet

As a simple example that uses a couple of Mesh modifiers, we create a single bullet using a hemisphere object. You can create this simple object in other ways, but this offers some good practice.

To create a bullet using the Face Extrude modifier, follow these steps:

  1. Select Create image from book Standard Primitives image from book Sphere, and drag in the Top viewport to create a sphere object. Set the Radius value to 60 and the Hemisphere value to 0.5 to create half a sphere.

  2. Right-click on the sphere object, and select Convert To image from book Editable Poly in the pop-up quadmenu to convert the hemisphere to an Editable Poly object.

  3. Select the Top viewport, right-click on the viewport name, and select Views image from book Bottom from the pop-up menu (or press the B key) to switch to the Bottom view.

  4. In the Selection rollout, click the Vertex button to enter Vertex subobject mode and enable the Ignore Backfacing option. Then select the single vertex in the center of the hemisphere, and press the Delete key.

  5. In the Selection rollout, click the Border button to enter Border subobject mode, and then click the edge of the hemisphere to select the border of the hole that was created by deleting the center vertex. Then click the Cap button in the Edit Borders rollout.

  6. Select the Polygon button in the Selection rollout to enter Polygon subobject mode and select the bottom polygon subobject. Then select Modifiers image from book Mesh Editing image from book Face Extrude to apply the Face Extrude modifier to the selected polygon face. Set the Amount value to 200.

  7. Select Create image from book Standard Primitives image from book Cylinder, and drag in the Bottom viewport to create a thin Cylinder object that is just wider than the extruded hemisphere. Then move the new Cylinder object until it is positioned at the end of the bullet object.

Figure 16.8 shows the completed simple bullet.

image from book
Figure 16.8: A simple bullet can be created by extruding one face of a hemisphere

Optimize modifier

The Optimize modifier isn't as robust as the MultiRes modifier, but it roughly accomplishes the same function-reducing the overall number of polygons. It does the opposite of the Tessellation modifier. It simplifies models by reducing the number of faces, edges, and vertices. The Level of Detail can be set differently for the Renderer and the Viewports. Face and Edge Thresholds determine whether elements should be collapsed. Other options include Bias and Maximum Edge Length. Parameters can also be set to Preserve Material and Smooth Boundaries. The Update button enables manual updating of the object, and the text field at the bottom of the rollout displays the number of vertices and faces for the current optimization.

Figure 16.9 shows an alligator model that has been optimized. Notice the dramatic reduction in the number of faces from the left to the right. Viewpoint Datalabs, known for producing high-resolution models, created this model. At the bottom of the Modify panel, you can see that the number of faces has been reduced from 34,404 to 10,140 faces by setting the Face Threshold to 15 and the Edge Threshold to 3.0. (I guess that would make the gator on the right "lean and mean.")

MultiRes modifier

You can use the MultiRes modifier to create lower-resolution versions of a mesh object. This modifier is especially useful for creating real-time updated meshes for the gaming market. Once applied to a mesh object using the Modifier List in the Modify panel, you can set the desired options in the Generation Parameters section of the MultiRes Parameters rollout and click the Generate button to apply the MultiRes solution to the selected object.

image from book
Figure 16.9: You can use the Optimize modifier to reduce the complexity of the alligator model

The Vertex Merging option maintains continuity between vertices within the mesh. When enabled, vertices within the Threshold value are welded as the mesh is reduced. The Within Mesh option collapses the boundaries of adjacent elements. The Boundary Metric option looks for boundaries where different materials are applied and tries to maintain these boundaries.

The MultiRes modifier includes a single subobject: Vertex. Using this subobject mode, you can select vertices that you don't want to change. These selected subobject vertices are not altered if the Maintain Base Vertices option is enabled. The Crease Angle value can be used to maintain sharp edges. If any of the options are changed, you can update the solution by clicking the Generation button again.

Once generated, you can use the Vertex Percent and Vertex Count spinners to control the mesh complexity. The viewport displays the updated mesh as you change its complexity. The rollout displays the number of vertices and faces. The Max Vertex and Max Face fields are the number of vertices and faces in the original mesh; the Face Count is the current number of faces.

Tutorial: Creating a MultiRes hand

You can use the Optimize modifier to quickly create the lower-resolution models, but the MultiRes modifier offers more functionality and enables you to dynamically dial down the resolution to exactly what you want. In this example, we use the MultiRes modifier on a high-res hand model created by Viewpoint Datalabs. The hand weighs in at 2,906 polygons, which is a little heavy for any game engine.

To create a MultiRes hand, follow these steps:

  1. Open the image from book MultiRes hand.max file from the Chap 16 directory on the DVD. This file contains a simple hand model.

  2. With the hand selected, choose MultiRes from the Modifier List to apply the modifier to the hand model.

  3. In the MultiRes Parameters rollout, enable the Vertex Merging option and set the Threshold to 0.05. Also enable the Boundary Metric and Multiple Vertex Normals options, and set the Crease Angle to 75. Then click the Generate button.

  4. Create a copy of the hand by holding down the Shift key and dragging the hand to the right. In the Clone Options dialog box that appears, select Copy, name the clone Hand - Lo, and click OK.

  5. With the cloned hand selected, set the Vert Percent to 10.

    Notice that the number of faces has dropped from over 2,906 to 302.

Figure 16.10 shows the results of the MultiRes modifier. If you look closely, you can see that the hand on the right isn't as smooth, but it still looks pretty good and the game engine won't complain.

image from book
Figure 16.10: You can use the MultiRes modifier to dynamically dial back the complexity of a mesh

Smooth modifier

You can use the Smooth modifier to auto-smooth an object. Smooth parameters include options for Auto Smooth and Prevent Indirect Smoothing along with a Threshold value. The Parameters rollout also includes a set of 32 Smoothing Groups buttons labeled 1 through 32. These same Smoothing Groups are available as options for the Polygon and Element subobjects.

Symmetry modifier

The Symmetry modifier allows you to mirror a mesh object across a single axis. You can also select to Slice Along Mirror and weld along the seam with a defined Threshold. The gizmo for this modifier is a plane, which matches the selected axis and the arrow vector that extends from the plane.

Tutorial: Creating symmetrical antlers

Using symmetry, you can create one half of a model and then use the mirror tool to create the other half. If you need to see the changes as you make them, you can use the Symmetry modifier. In this example, we've taken the antlers off an elk model so you can practice putting them back on.

To create a set of symmetrical antlers, follow these steps:

  1. Open the image from book Elk with short antlers.max file from the Chap 16 directory on the DVD. This file contains an elk model created by Viewpoint Datalabs with its antlers removed.

  2. With the hide object selected, select the Modifiers image from book Mesh Editing image from book Symmetry menu command to apply the Symmetry modifier. Its default setting has the X-axis selected, which places a plane running down the center of the elk model.

  3. In the Modifier Stack, select the Editable Poly object and enable the Polygon subobject mode. Then rotate the view until you're looking at the elk from behind its head. Select a polygon on the left side of the elk where the antler should be located.

  4. In the Edit Polygons rollout, click the option dialog box button for the Bevel tool. Set the Height value to 2.0, the Outline Amount to 0.15, and click OK.

  5. With the polygon still selected, move the beveled polygon outward away from the elk's head.

  6. Disable the polygon subobject mode and click on the Symmetry modifier in the Modifier Stack to see the symmetrical antler.

Figure 16.11 shows the results of the Symmetry modifier.

image from book
Figure 16.11: When you use the Symmetry modifier, you have to model certain objects only once

Tessellate modifier

You use the Tessellate modifier to subdivide the selected faces for higher-resolution models. You can apply tessellation to either Triangle or Polygonal faces. The Edge option creates new faces by dividing the face from the face center to the middle of the edges. The Face-Center option divides each face from the face center to the corners of the face. The Tension setting determines whether the faces are convex or concave. The Iterations setting is the number of times the modifier is applied.

Caution 

Applying the Tessellate modifier to an object with a high Iterations value produces objects with many times the original number of faces.

Vertex Weld modifier

The Vertex Weld modifier is a simple modifier that welds all vertices within a certain Threshold value. This is a convenient modifier for cleaning up mesh objects.




3ds Max 9 Bible
3ds Max 9 Bible
ISBN: 0470100893
EAN: 2147483647
Year: 2007
Pages: 383

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