By Joe Greco
Over the past few years, as more users have begun to employ laser scanners for applications such as reverse engineering, the need for software that can work with the thousands of points produced by these devices has increased. Paraform, introduced last year by the company of the same name, is designed to read in these point clouds and eventually turn them into watertight NURBS surfaces that can be used in a CAD program such as Pro/Engineer or Alias Studio. In June of this year, the company released Paraform 2.0.
Paraform opens by default to four standard views. At the top of the screen are familiar Windows menus and toolbars as well as commonly used Paraform tools, such as those for selecting and viewing data. There is also a series of tabs representing the different steps in the Paraform workflow-clouds, meshes, curves, surfaces, and so on. On the left are tools that relate to the current mode, while the right side displays a browser where users can control the visibility of entities.
|Paraform's user interface follows Windows standards. This image shows a cloud with 150,000 points being reduced to half that many.|
The entire process starts by importing a point cloud file. Since these files can contain more than 250,000 points, the next step is usually to reduce this number, a process called decimation. When decimating, Paraform is smart enough to leave more points in curved areas while taking away more in planar sections, essentially preserving more detail.
The next step is to create polygons from the points, resulting in a polymesh, a simple matter of just selecting the point cloud and picking the triangulate button. Some scanners include software that also can handle this function; Paraform can import the polymesh created by such programs, too.
Paraform provides tools to automatically find gaps that might have formed during the polymesh creation or were in the point cloud scan to begin with. After the software finds holes, the user can step through, hole by hole, and fill them. There is also a tool that fills all holes automatically, but it attempts to close surfaces that should be left open as well.
It is easy to return to cloud mode and re-mesh based on a lower point density so that you can determine if the same-quality mesh can be achieved from fewer points. However, there is no way to save polymeshes-the new triangulation just replaces the old, unless the point cloud is first duplicated.
Before moving to the next step of creating the curves that will eventually form the NURBS, you can work with the polymesh using several tools. A new section tool shows an interactive cross section at any point, for instance, and number tools enable you to dynamically sculpt and shape the mesh.
The trickiest part of the entire process is creating the curves that form the outlines of the NURBS patches. That is why in version 2.0, Paraform has added feature extraction, which does this almost automatically. An other new feature allows the curves to be saved and reused in similar designs. In addition, several new, powerful Design for Manufacturability (DFM) functions, including the creation of parting lines and the removal of un der cuts, are available as well. Another new feature enables you to remove rounded corners and replace them with sharp edges.
From these curves come string patches, which are structured polygons suited for finite-element ana lysis, visualization, and milling ap plications. Although creating the string patches is a manual and tedious process, once they're created, the software automatically develops the NURBS patches from them. To make the curves of neighboring NURBS patches line up, Paraform provides a tool that enables you to simply drag from one patch to the adjacent one. With the NURBS surfaces completed, they can be exported to CAD.
In addition, the surfaces can be offset and capped to create a solid. There is even an option that enables users to specify a tolerance, meaning the software will vary the wall thickness to accommodate different conditions. Paraform also can add holes to the solid geometry. And it contains inspection tools that enable users to compare the original point cloud to the surface or solid model.
It should be noted that all these steps are associated, meaning that going back and editing the polymesh updates the NURBS surface. Conversely, even before NURBS exist, a user can "jump ahead" to the curve mode and use NURBS to help sculpt a polymesh.
Overall, Paraform's tools, workflow, and price are similar to Studio from Raindrop Geo magic and RapidForm by Inus Tech nology. Each one has its advantages and disadvantages, but Paraform has the most impressive DFM-related tools and is the only one that can build solids. Like the others, certain aspects of the software could be a bit easier to use, and the undo capabilities are limited, though improving. But the wealth of features makes Paraform a good solution for creating 3D geometry from point clouds, and a versatile tool for many other aspects of the modeling process as well.
Joe Greco specializes in CAD and 3D programs. You can reach him at firstname.lastname@example.org.
Price: Starts at $18,000
Minimum system requirements: Windows NT/2000 or Irix; 256MB of RAM; basic OpenGL card
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