Lucid Shape Catia V5 Geometry Transfer

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Paper #023-1

LucidShape Catia™ V5 Geometry Transfer Copyright © 2007 Brandenburg GmbH

Abstract

This paper describes a convenient way to transfer Catia™ V5 geometry to LucidShape‘s canonical axis system and back, where the Catia™ geometry may be arbitrarily positioned in world coordinates. The key approach is to let the user define a suitable local axis system (the CATPart axis system) in Catia™, representing a transform to be applied to the geometry on its transfer between Catia™ and LucidShape. The approach is discussed on a detailed example.

Introduction

The interchange of geometry data between various tools like Catia™ V5 and LucidShape is a common task in the development of optical systems. As a typical scenario, one could have an arbitrarily positioned CATPart (like a reflector cavity) in Catia™ which should house a reflector to be designed with the help of LucidShape‘s lighting technology. Once the reflector is computed, its geometry has to be transferred to Catia™ in a way that it fits exactly into the CATPart. In some cases, one would also have to transfer the CATPart to LucidShape prior to the reflector computation, because the CATPart may be indispensable for the computation (for example because it significantly affects simulation results). That transfer must also be carried out in a way that positions the CATPart well into LucidShape‘s optical axis system.

Transfer via a local Catia™ axis system

The need for proper positioning makes a direct transfer of geometry between Catia™ and

LucidShape unadvisable. The CATPart’s position in Catia™ may be incompatible with LucidShape‘s optical axis system (the CATPart may lie “somewhere far out”), or the reflector may be incompatible with the CATPart position in Catia™. Therefore, a suitable linear transform is needed to align the CATPart position and LucidShape’s optical axis system to each other. That linear transform will usually be available as a local axis system to the CATPart; therefore we denote it as a CATPart axis system (or in short CATAX). Once a CATAX is available, it can be communicated to LucidShape. We could then either a) replace LucidShape‘s optical axis system by the CATAX, or b) use the CATAX to transform the CATPart to LucidShape‘s default axis system. In fact, both ways are nearly the same from the viewpoint of usability. In LucidShape, we prefer approach b) for conceptual reasons (no change of the default axis system is needed). If this is not the case, its setup is a task best to be handled interactively in Catia™. In practice, the procedure is as follows:

1. In Catia™, make sure a suitable CATAX is available. If this is not the case, create one. Its z-axis should correspond to the CATPart’s optical axis.

2. In LucidShape, communicate with Catia™ to select a CATAX.

3. If necessary, transfer the CATPart to LucidShape‘s optical axis system. The CATPart will be transformed with the CATAX on its transfer. CATAX selection and transfer is assisted by a special transfer dialog.

4. In LucidShape, construct the optical geometry so that it fits into the CATPart. Due to the CATAX transformation, the construction can be carried out in LucidShape‘s optical axis system.

5. In LucidShape, communicate with Catia™ to select the same CATAX again which was used in step 2. Then transfer the new


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reflector to the original Catia™ world cordinates.

Application to a model example

The procedure described above will now be discussed on a model example. In Catia™, we have a headlamp cavity as a CATPart which is intended to house two round reflectors to be computed in LucidShape. Each of the two reflectors’ places is already equipped with a local axis system (in the image below highlighted by coloured circles), which we may take as CATAXes for geometry transfer between LucidShape and Catia™.

The first step now is to compute the two reflectors in LucidShape’s optical axis system. For the sake of

simplicity, we will not import the cavity into LucidShape (that is, we will omit step 3. in the introduction), and we will replace a proper headlamp design at this point by simply creating two round paraboloids fitting into the cavity places. Thanks to the two CATAXes available with the CATPart, we may create each of the two paraboloids in LucidShape’s optical axis system by using the standard surface generation tools.

A CATPart in Catia™, to be used as a cavity for two round reflectors computed in LucidShape


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The rotational paraboloid dialog The above image shows the rotational paraboloid dialog for which the only relevant parameters left are the paraboloid’s inner radius (which we set to

10mm for the lampholder hole), outer radius and focal length (which we set by measuring the appropriate values from the CATPart in Catia™). Now, as we have “designed” the reflectors, we start the Catia™ LucidShape transfer utility to connect to Catia™. For each of the two

The Catia™ LucidShape transfer utility. The imported

CATAX matrix is denoted by a red frame here.

The two rotational paraboloids, to be transferred to Catia™


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reflectors, we select its CATAX (which may occur either in LucidShape or in Catia™) and transfer the reflector to Catia™. Transformation with its CATAX makes sure that each reflector becomes located in its right place in the cavity, as can be seen from the image below.

Conclusion

When transferring geometry between different tools like Catia™ and LucidShape, it is important to match the tools’ axis systems. For example, a Catia™ CATPart object located somewhere in world coordinates may not match with LucidShape‘s optical axis system. A key approach to this problem lies in selecting suitable local axis systems for the Catia™ CATPart, which may serve as transformations to get the Catia™ geometry into LucidShape‘s optical axis system and to re-transfer it back to its right place in Catia™ later. To clearify this approach, we have discussed the procedure in detail by application to a significant example model.

Contact Info

Brandenburg GmbH Technologiepark 19 33100 Paderborn, Germany Phone: 49 5251 681500 Fax: 49 5251 681520 [email protected] http://www.lucidshape.com/

The CATPart in Catia™ with its new reflectors

Documents

Lucid Shape Catia V5 Geometry Transfer