July 19, 2004
JT Open Initiative Continues To Attract New Members
Please note that contributed articles, blog entries, and comments posted on MCADcafe.com are the views and opinion of the author and do not necessarily represent the views and opinions of the management and staff of Internet Business Systems and its subsidiary web-sites.
Jeff Rowe - Managing Editor

by Jeff Rowe - Contributing Editor
Each MCAD Weekly Review delivers to its readers news concerning the latest developments in the MCAD industry, MCAD product and company news, featured downloads, customer wins, and coming events, along with a selection of other articles that we feel you might find interesting. Brought to you by MCADCafe.com. If we miss a story or subject that you feel deserves to be included, or you just want to suggest a future topic, please contact us! Questions? Feedback? Click here. Thank you!

Face visibility hints - In certain circumstances, applications may have prior knowledge about the visibility status of some of the faces in a model. For instance, an inaccurate hidden line technology used for fast visualization on large models, such as a z-buffering technique, can determine that some faces are not visible in a particular view. It is now possible for an application to provide such information to the HLM in order to accelerate the calculation of an accurate hidden line view of an entire model.

Improved boxing - For each part in an assembly, applications that employ HLM can specify a box that completely encloses a part. The HLM uses boxes to reduce the time it takes to compute a hidden line view. Generally, the more closely the box matches a part, the better the possible performance gain. In previous releases, only axis-aligned boxes were permitted. It is now possible to specify an axis-aligned box that has been transformed to enclose a part more precisely.

The new enhancements to D-Cubed's latest release of its Collision Detection Manager (CDM), the leading interactive collision detection and clearance computation component for accurate models in assembly environments, include:

Identification of touching entities - The CDM previously only detected those collisions where the colliding bodies share a common volume. This is not the case when entities are touching - previously, such cases were ignored. In this release the CDM has been extended to enable applications to detect any entities that are touching, as well as those that interpenetrate.

Faster computation of touching solutions between moving parts - When the CDM is used for interactive collision detection between moving parts, collision checks are systematically performed as the parts are moved through a series of small but discrete steps. When moving parts collide, they will generally have moved from a non-colliding state to an interpenetrating state in a single step. Applications can then request the CDM to determine the exact positions at which the two parts would touch. The new release implements more sophisticated algorithms to speed up this calculation. The original function used a bi-section algorithm that often required many steps to converge on the touching
solution. The new algorithm is much more efficient, requiring very few steps without any compromise on reliability. Among other applications, the computation of touching solutions between colliding parts is useful for presenting possible face mating conditions to the end-user.

Improved boxing - For each part in an assembly, applications can specify a box that completely encloses a part. The CDM uses boxes to reduce the time taken to compute collisions. Generally, the more closely the box matches a part, the better the possible performance gain. In previous releases, only axis-aligned boxes were permitted. It is now possible to specify an axis-aligned box that has been transformed to enclose a part more precisely.

The HLM and CDM technologies were both first released in 1999 and have enjoyed widespread adoption across the MCAD spectrum, providing many core capabilities. The HLM is one of the most widely deployed hidden line methods in the CAD industry According to D-Cubed, its kernel independence lets a dedicated team of experts focus exclusively and continuously on the development of its advanced hidden line algorithms without being distracted by the wider requirements of a general solid modeling technology. Since its initial release, CDM has achieved broad market acceptance, particularly with mainstream mechanical CAD applications, including Autodesk Inventor, Solid Edge, and SolidWorks, among
several others. CDM's success is largely due to its range of clever algorithms specifically designed to detect collisions and compute clearances on accurate solids in an interactive assembly environment, rather than being derived from the traditional - and unnecessarily computationally intensive - Boolean approach. Commonly used in conjunction with D-Cubed's 3D DCM assembly-part-positioning and kinematic-solving component, the CDM provides interaction with assembly models with a greater sense of realism and solidity, eliminating design errors and failures caused by interpenetrating parts.

Jeffrey Rowe is the editor and publisher of MCADCafé and MCAD Weekly Review. He can be reached at
Email Contact or 408.850.9230.

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