To select different types of component simultaneously, first select the components of one type, press Shift while changing the selection filter, and then add the other components to the selection.
When working with polygon meshes, there are some basic concepts you should understand.
A polygon is a closed 2D shape formed by straight edges. The edges meet at points called vertices. There are exactly the same number of vertex points as edges. The simplest polygon is a triangle.
Polygons are classified by the number of edges or vertices. Triangles and quadrilaterals (or quads) are the most commonly used for modeling. Triangles have the advantage of always being planar, while quads give better results when used as the basis of subdivision surfaces. Certain game engines require that objects be composed entirely of triangles or quads.
Polygons that are very long and thin, or that have extremely sharp angles, can give poor results when deforming or shading. Polygons that are regularly shaped, with all edges and angles being almost equal, generally give the best results.
A polygon mesh is a 3D object composed of one or more polygons. Typically these polygons share edges to form a three-dimensional patchwork.
However, a single polygon mesh object can also contain discontiguous sections that are not connected by edges. These disconnected polygon “islands” can be created by drawing them directly or by combining existing polygon meshes.
Types of Polygon Mesh Components
Polygon meshes contain several different types of component: points (vertices), edges, and polygons.
• Points are the vertices of the polygons. Each point can be shared by many adjacent polygons in the same mesh.
• Edges are the straight line segments that join two adjacent points. Edges can be shared by no more than two polygons.
Edges that are not shared represent the boundary of the polygon mesh object and are displayed in light blue if Boundaries and Hard Edges are visible in a 3D view.
• Polygons are the closed shapes that make up the “tiles” of the mesh.
Viewing Polygon Mesh Components and Attributes
You can display or hide polygon mesh components, like points and boundaries as well as other attributes, in the 3D views in exactly the same way as other components and attributes. A quick summary is provided here, but for complete details about viewing, see Viewing 3D Objects [Interface and Tools].
To display or hide components in a single 3D view
Do one of the following:
• Click the eye icon (Show menu) and choose the corresponding component option. You can press Shift to keep this menu open while you toggle multiple items.
or
• Press Shift+s, or click the eye icon and choose Visibility Options. The Camera Visibility property editor contains many more options than the menu, for both selected and unselected objects.
To display or hide components in all open 3D views
Do one of the following:
• Choose Display on the main menu, and then choose the corresponding component option.
or
• Choose Display > Visibility Options (All Cameras). The Camera Visibility property editor contains many more options than the menu for both selected and unselected objects.
Selecting Components on Polygon Meshes
You can select and work with points, edges, and polygons in the same way as any other type of component using the filters on the Select panel. Selection is fully described in Selecting [Scene Elements], and is quickly summarized here.
In addition, there are some commands that apply only to polygon mesh components and are described in this chapter — see Selecting Polygon Mesh Components.
To select components
1. Select the object that owns the components you want to select.
To select components on multiple objects, select all the associated objects first.
2. Set the selection filter to the desired component type. See Summary of selection filters.
3. If desired, change the selection tool. See Summary of selection tools.
4. Click and drag on the components in a 3D view.
The specific mouse buttons and modifier keys that you use to perform different actions — like selecting, adding to the selection, toggling, and deselecting — depend on the selection interaction model.
For more complete details, see Selecting Components Using the Different Interaction Models [Scene Elements].
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To select different types of component simultaneously, first select the components of one type, press Shift while changing the selection filter, and then add the other components to the selection. |
Component selection filters determine what type of component you can select on the active geometric objects. The most commonly used filters are available as buttons on the Select panel, while more filters are available from the Filter menu below the buttons.
The component selection filters are context-sensitive; they change depending on what type of object is active. The illustration below t shows the component filters available from the buttons when a polygon mesh is selected.
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There are additional filters on the Filter menu that allow you to select, for example, border points or edges. These are examples of custom filters. For information about creating your own filters, see the SDK Guide. |
The selection tools determine the mouse interaction used select elements. You can activate a selection tool with the items on the Select > Tools menu.
Alternatively, you can press one of the following keys:
• F7 for the Rectangle selection tool.
• F8 for the Lasso selection tool.
• F9 for the Freeform selection tool.
• F10 for the Raycast selection tool.
• Shift+F10 for the Rectangle-Raycast tool.
• F11 for the Paint selection tool (points, polygons, and edges only).
Summary of selection modes
Selection modes are combinations of a filter and tool mapped to a single key for convenience. Use any of the following keys:
• t for Rectangle Point mode.
• e for Rectangle Edge mode.
• i for Raycast Edge mode.
• y for Rectangle Polygon mode.
• u for Raycast Polygon mode.
Selecting Points that Overlap Others
Polynode bisectors can be useful when selecting or moving points that overlap others on a polygon mesh object.
To select or move a point that overlaps others
1. Open the Camera Visibility property editor of a 3D view, for example, by pressing Shift+s.
2. On the Components tab, set Show Polynode Bisectors to Show While Drawing Points.
With this option, bisectors are displayed as small purple lines at the corners of polygons whenever points are visible.
3. Activate point selection (for example, press t for Rectangle Point Selection) or the Tweak Component tool (press m).
4. Click on a bisector to affect the corresponding point.
Planar and Non-planar Polygons
When an individual polygon on a polygon mesh is completely flat, it is called planar. All its vertices lie in the same plane, and are thus coplanar. Planar polygons give better results when rendering.
Triangles are always planar because any three points define a plane. However, quadrilaterals and other polygons can become non-planar, particularly as you move vertices around in 3D space. When objects are automatically tessellated before rendering, non-planar polygons are divided into triangles. However, other applications such as game engines may not support non-planar polygons properly.
When adding new polygons, there is a preference setting that prevents you from drawing non-planar polygons: see Adding and Editing Polygons (Drawing).
Softimage has strict rules for valid polygon mesh structures and won’t let you create an invalid mesh. Some of the rules are:
• Every point must belong to at least one polygon.
• Every edge must belong to at least one polygon.
• A given point can be used only once in the same polygon.
• All edges of a single polygon must be connected to each other. Among other things, this means that you cannot have a hole in a single polygon. To get a hole in a polygon mesh, you must have at least two polygons.
• Edges cannot be shared by more than two polygons. Tri-wings are not supported. To connect three polygons in this way, a double edge is required.
• Softimage does support one case of non-manifold geometry. A single point can be shared by two otherwise unconnected parts of a single mesh object.
If you export geometry from Softimage, remember that such geometry may not be considered valid by other applications.
Materials and Textures on Polygon Meshes
In addition to basic materials and textures, polygon meshes support a couple of specialized shading features:
• Local materials and textures on polygon clusters: This lets you apply a material or texture to specific polygons on an object. For more information about local materials and textures, see Assigning Materials to Selected Polygons and Polygon Clusters [Material and Shader Basics].
• Vertex colors: This is a shading technique that stores color information in the vertices, allowing for fast shading in certain game engines. For more information about color at vertices, see Vertex Colors [Texturing].
Preserving Textures While Modeling
Most modeling operations on polygon meshes are texture-safe and preserve existing texture projections. However, you may encounter some problems where there are texture seams.
For example, if you collapse an edge that crosses a texture seam, the new merged point uses the average texture UVs of the previous two points and the result may not be visually correct.
Autodesk Softimage v.7.5