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Material/colors for .step files
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* October 13, 2009, 12:48:36 PM
An electrical engineer by trade, I am working on creating 3D models of electronic components (IC's, connectors, LED's, etc.) for our ECAD system (which uses STEP format) to produce realistic looking board models for my company's clients. I have found a great resource in 3D Content Central, but they don't have all of the models I need and waiting for a request to be filled is troublesome at times.

I have TC 15.2 Pro installed. Any time that I open a .step file in TC, I find that the model is completely black.

I have followed the instructions from several posts to remove all material assignments in Facet Edit mode and then assign materials to various objects/facets (depending on the construction of the model that I downloaded). Every time that I re-export in step format, my ECAD system sucks in a solid colored model (I know it is not an issue with the ECAD software because I can import multicolored STEP models from other sources without problem). I then open the model in TC again, and all material assignments are lost or at least the colors associated with them!

So, I created a rudimentary SOT-143 IC from scratch as a .tcw, set the pins of the device to Metals > Chromium and the body to Plastics > Plain Black. When I save the TCW out as a STEP file, I get the same results as though I started out with a STEP model!

I have also tried starting out from .sat format models and get the same results.  I managed once to close and reopen a .sat file in TC without losing material/color information. When I uploaded the file to 3DCC, the model appeared as one solid color (Chromium).

I would really appreciate any assistance I can get with determining how to create a STEP or SAT format file that does not lose its color information when it is exported or to understand that this is an inherent limitation in TC 15.2.

I have attached the SOT143 tcw format file for reference if anyone is interested. Perhaps there is a project setting that I am missing. Admittedly, I do not spend very much time working in TurboCAD.

Best Regards.

[attachment deleted by admin]


* October 15, 2009, 05:16:59 AM

I have done some digging into this issue and have found the following for anyone interested. TurboCAD does not appear to set the units conversion factor or the color associated with an assigned material in exported STEP format files.

For example (NOTE that I am referencing the ISO-10303 AP214 schema for STEP files):
This fixes the scaling issues when the drawing is created in inches in TurboCAD:
-I created a drawing in units of inches, but the exported STEP file was set to units of millimeters. I fixed this in a text editor by changing the following entities:
--CONVERSION_BASED_UNITS(), the first parameter is changed to INCHES. (This is jsut a label, so it has no direct impact on the model, but should be changed for correctness and completeness.)
--LENGTH_MEASURE_WITH_UNIT(), the first parameter is changed to LENGTH_MEASURE(25.4). (This sets the conversion 25.4 mm = 1 inch).

This fixes the colors in the STEP model:
TurboCAD appears to default all color assignments in a STEP model to BLACK (i.e. COLOUR_RGB('',0.0,0.0,0.0))
The three decimal values represent Red, Green, and Blue respectively with values between 0.0 and 1.0.
So If I use the Metals > Chromium assignment for pins on an IC, then I expect the STEP model to be populated with COLOUR_RGB('Chromium',0.68,0.68,0.68) for every facet of the pins.

This brings me to my request to TurboCAD to fix the tool, since every facet must have its color set, it is a very tedious task to manually edit the colors in a text editor because even on the simplest of designs (a 4-pin IC for example), there are many facets to change (60 - 70 in the attached file) and there is no way to identify what facet is being changed with out editing the ASCII text and loading the model in a viewer to see if the correct facet was changed.

For what it is worth, I believe there is a similar issue in the way TurboCAD exports to SAT files, but I have not dug into that one very deep. I have only observed one occurance where the colors were imported incorrectly and stopped there since my focus was on the STEP format.

I have submitted a ticket to TC Support. Hopefully I can message the perceived issues correctly and see at least an acknowledgement that the issues exist.