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How MeshSmooth Works

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  1. Surface Development Using the MeshSmooth Modifier
  2. MeshSmooth Modifier Rollouts
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With the 3ds max 4 MeshSmooth modifier, you can develop sophisticated surfaces, edges, and corners of the objects you're modeling. This article by art director and industrial designer Duane Loose gives you an inside look at the tool's capabilities.
This article is excerpted from 3ds max 4 Workshop.
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MeshSmooth is one of the everyday tools used in 3ds max 4 modeling. Understanding how MeshSmooth works, coupled with understanding the elements of organic form and surface development, will enable you to make full use of this modifier.

This article deals exclusively with the basic controls affecting the MeshSmooth NURMS subdivision method. For an explanation of other subdivision methods and their related control rollouts and the rollouts not covered here, press F1 to access the 3ds max 4 User Reference or consult your user manuals.

Surface Development Using the MeshSmooth Modifier

The surfaces of the polygon mesh models you'll create in 3ds max 4 are constructed from basic building blocks called subobjects—vertex, edge, face, and polygon. The intrarelationship of the subobjects determines the size, shape, and dimensional detail of the object you are modeling. Surface development is the study of how surfaces intersect and transition from one surface to the next, and MeshSmooth is one of max 4's primary surface development tools.

MeshSmooth is a subdivision surface modifier that adds extra faces to a surface mesh to smooth the intrasurface transitions. This allows you to create sophisticated organic forms such as automobiles, humanoids, and other creatures.

Basic Process: Using Source Objects and Reference Clones

Although the MeshSmooth modifier can be applied to any object that you create in max, it's used to best effect when applied to a Reference clone of a source object. Using an object as a source to control the form or animation of another is a powerful technique that you'll use to great benefit in your max work. The following steps outline the suggested process to follow when using the MeshSmooth modifier:

  1. Make sketches or storyboards to understand your model's form and function.

  2. Create a source object—it can be any editable mesh or an object to which an Edit Mesh modifier has been applied. Experience with the technique has shown that it's best to use a primitive parametric object that approximates the size and shape of your intended design. Primitive parametric objects are spheres, cones, boxes, and so on.

  3. Convert the primitive to an editable mesh, or add an Edit Mesh modifier to it. This enables you to access and use mesh subobjects to control the effect of the MeshSmooth modifier and the resultant form of your model. If you use the Edit Mesh modifier instead of converting the object to an editable mesh, you'll retain the original parametric creation parameters that were used to create the object. These parameters can then be adjusted to affect the form of the model as well.

  4. Make a Reference clone of the source object.

  5. NOTE

    A Reference clone is a one-way instance of the source object. This means that any changes that you make to the geometry of the source object will also change the Reference clone. However, changes to the Reference clone will not affect the source object.

  6. Add the MeshSmooth modifier to the Reference clone.

  7. Modify the source object to create the form you are trying to achieve.

  8. Refine the form of the Reference clone by adjusting the control parameters in the MeshSmooth modifier command panel rollouts.

To change the source object, you can adjust its creation parameters, such as length, width, surface segments, and so on. Or, you can use the subobject commands such as extrude, bevel, chamfer, and so forth in the Edit Mesh modifier command panel rollouts.

Digital Clay: Understanding the MeshSmooth Effect

The max User Reference notes the following:

The MeshSmooth modifier smoothes geometry in your scene by adding faces at corners and along edges. The effect of MeshSmooth is to round over corners and edges as if they had been filed or planed smooth. When you apply MeshSmooth, an extra face is added for every vertex and edge.

This is an adequate explanation, but it still doesn't impart the necessary intelligence to enable you to bend the effect to your artistic will. Through experimentation and experience with the technique, I've found that MeshSmooth looks at the entire surface and evaluates how each individual polygon relates to the adjacent polygons surrounding it. It then applies its smoothing algorithm to the polygons with respect to their position and orientation within the mesh.

For example, a box object, with length, width, and height segments set to 1, has six equilateral surfaces that are perpendicular and non-coplanar. When MeshSmooth is applied to this simple form, it creates a spherical surface—the smoothest possible transition between the non-coplanar sides of the box (see Figure 1).

Figure 1 MeshSmooth uses the interrelationship of surface polygons to determine the transition between adjacent surfaces.

Another way to explain the effect of MeshSmooth is to describe it in terms of planar, edge, and corner surface transitions.

Surface Transitions: Edges and Corners

On any given surface, there are basically three types of adjacent polygonal states that can describe how the surfaces interrelate: edge transitional surfaces, corner transitional surfaces, and contiguous coplanar surfaces.

Edges are created when two non-coplanar surfaces intersect, and corners are created when three non-coplanar surfaces come together. When adjacent polygons intersect at an edge or corner, MeshSmooth creates a surface transition between the adjacent polygons. The shape of the surface transition is based on the dimensional and spatial relationship of the polygons that define the edge or corner. Contiguous coplanar surfaces are created from adjacent polygons that are neither edges nor corners (see Figure 2).

Figure 2 Coplanar is the term that describes polygons that reside in the same plane as the adjacent polygons surrounding them. MeshSmooth subdivides these coplanar polygons, creating more coplanar faces.

Surface Boundaries: Understanding Tangents

When an edge or corner surface transition is created, a boundary in the developed surface describes where the transition begins and ends. This boundary is referred to as a tangentÑthe point at which an edge or corner surface begins and ends its transition (see Figure 3).

Figure 3 Transitional surface boundaries define the beginning and ending of transitional surfaces. The transitional surface also determines the shape of highlights that appear in the form.

You can change the size and shape of the boundary tangents by manipulating the subobjects in the source object that controls the surfaces of the Reference clone. In Figure 4, the vertices indicated were selected in the source object mesh and scaled down to create the pinched surface and resultant highlight seen in the corner of the Reference clone.

Figure 4 Selecting and transforming subobject vertices, edges, and polygons is the fundamental technique behind developing organic form using the MeshSmooth modifier.

Subtle and bold manipulations of the mesh subobjects to modify the edges, corners, and coplanar surfaces of your models will enable you to create any shape you can imagine. Selecting and modifying the vertices and polygons of the box primitive in the left side of the image created the alien head in Figure 5. This is the power of MeshSmooth in action.

Figure 5 The vertices and edges of the source object and the settings in the MeshSmooth rollouts determine the effect of the MeshSmooth modifier.

Source Object Parameters

The parameter variables that control the MeshSmooth effect include the dimensions of the source object and the number of length, width, and height segments used in the source object creation parameters.

Figure 6 shows how changing the number of segments in the source object affects the MeshSmooth effect.

Figure 6 Increasing the length, width, and height segments of the object to which the MeshSmooth modifier is applied changes the effect of the modifier.

Source Object Type

The basic proportional dimensions of your source object and the primitive object type that you choose are also important considerations when you use this technique. A sketch of your intended design will help you choose an appropriate source object, one that most closely resembles the finished model you are trying to achieve. Figure 7 shows how MeshSmooth affects different primitive source objects.

Figure 7 Knowing which primitive object to choose for your source is a matter of experimentation and experience. Some artists start with a box primitive object for every MeshSmooth model they create.

MeshSmooth Concept Summary

Here's a recap of the important basic MeshSmooth concepts and principles:

  • Choose a primitive object that resembles the finished model form you are trying to achieve.

  • MeshSmooth applies a smoothing algorithm to create blended transitional surfaces at the edges and corners of your model. It does this by adding faces to every vertex and edge in the surface mesh.

  • Vertex, edge, face, and polygon subobjects can be transformed, extruded, beveled, and so forth to affect the organic surface development of the model. Access the subobjects and the edit commands in the Edit Mesh rollouts of the Modify command panel.

  • Changing source object creation parameters will affect the surface development of the Reference clone. Retain the source object creation parameters by adding an Edit Mesh modifier to the source object instead of converting it to an editable mesh.

  • Surface development is the conscious manipulation of surface-to-surface, edge, and corner transitions to control highlights and reflections. Design your models with their reflective and highlight patterns in mind, and pay attention to how the edges and corners of your models are developed.

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