Tips For Creating a Good VRML Model

Nearly all CAD/CAE packages allow for the export of models to VRML 2.0 (wrl) format. Some support this via a Save As option and others have an Export option. This varies from package to package. Most of these packages also have some limited mesh generation capabilities, meaning that the package automatically creates a simple mesh for the VRML. The quality and density of this mesh determines how well this VRML file will work in NI INSIGHT.

Elongated Polygons

Elongated Polygons are a common problem for most CAD/CAE applications. The surface of the VRML file is composed of triangles or squares. If these triangles or squares are elongated, thus not mostly uniform, then any interpolation scheme will be distorted by the mesh. The interpolation schemes normally use the distance between points or nodes along the connecting lines for distance calculations.

Many of the CAD/CAE packages support functions to add ‘split lines’ or additional points that can be used in the creation of the mesh. Many also have support for controlling the density of the mesh. Using these tools can eliminate most elongated polygons. See your CAD/CAE package for documentation of these functions.

Multiple Surfaces

Some CAD/CAE packages actually create multiple surfaces for the same area as the model is created. This varies from package to package and is normally not an issue for solid models. When the model is converted to VRML these multiple surfaces become problematic. The multiple surfaces can cause odd display variations and make selecting the correct point difficult.

Some CAD/CAE packages have controls for what surfaces are used when creating your VRML model. NI INSIGHT also comes with an Optimizer tool for VRML files which eliminated most multiple surfaces. In addition there are third party model converter tools that can be used to remove multiple surfaces.

VRML 1.0 or Non Standard VRML files

Occasionally a CAD/CAE package will not create VRML 2.0 files but VRML 1.0. Other are supposed to create VRML 2.0 files but do not create them correctly or use some sort of non standard format for the VRML file. These files will often not display or will display incorrectly in NI INSIGHT.

There are third party tools that can be used to convert from VRML 1.0 and sometime from non standard VRML to VRML 2.0.

Other Issues

Sometimes the CAD/CAE package just cannot produce a usable VRML model with a usable Mesh. In these cases there are often add-on tools to the CAD/CAE package or third party tools that can be used to generate a better mesh. In general NI INSIGHT requires a similar mesh to any model simulation/FEA package. Another option is to save the model in another format, such as Stereolithography (STL), and convert to VRML using a third party model conversion utility. This will often result in a cleaner resulting model in some CAD/CAE packages.

Things to look for in a good VRML model

· A uniform mesh with no severely elongated polygons
· A mesh with a high enough density of nodes to show the detail you are looking for (varies based on the detail of the model and haw many channels will be displayed)
· A mesh without multiple surfaces.

2 ratings | 2.50 out of 5

Print

Reader Comments | Submit a comment »