I have been struggling for some days to properly visualise and inspect a BricsCAD .dwg model of a large steel structure.
I am doing this by looking at the model (made with 3d solids) on screen in some model space viewports.
The assembled model consists of about 8 components, each from a separate .dwg file, each having sizes ranging from 50 to 300 kB. The components are x-ref into an assembly .dwg file, which is only about 50 kB since it has little content of its own.
When I view the individual components of the assembly , the shaded images display correctly using and shade mode. I can orbit, zoom and inspect the detail of the model.
When I view the assembly .dwg, which contains the components as x-refs, the shaded image display shows front and back faces and internal faces mixed up. The back faces obscure the front faces and prevent proper inspection of the assembly. All versions of the shaded image (flat, Gouraud, realistic, modelling) have numerous artefacts, the viewport frame overlaps the image, faces have patchy colour, portions of the image move (shatter) independantly and the shaded image is effectively unusable for inspecting the CAD model.
I spent a day doing experiments on 3 PCs with different graphics cards. BricsCAD on 2 PCs and AutoCAD 2011 on another. Eventually gathered enough information to identify the problem. The issues in this case are :
1) The dimensions of the drawn objects are significant. The components are less than 10 000 drawing units on any axis, while the assembled x-refs produce a model which is over 20 000 mm on one axis.
2) I reduced the number of layers in the components and the assembly .dwgs by cleaning up, purging and auditing them, and it made no noticable difference. There were about 100 layers in the assembly .dwg.
3) The size of the dwg file is not an issue for the CPU here. The PC on which the problem first manifested has a Xeon CPU with 8 GB RAM and BricsCAD only uses about 0.5 GB of that.
4) I concluded that my graphics card does not have the number-crunching resolution to process the image. The graphics card is a "gaming card" Nvidia GTX 740 with 2 GB Graphics RAM and 2 monitors attached. (I checked driver version and downgraded the Nvidia driver from V376.09 to 344.11 as recommended by REDSDKINFO, but that did not solve the problem).
I have viewed the .dwg model in BricsCAD on another PC with Intel Graphics 3000 (in the CPU) and the problem of broken shaded views occurred there too.
I have saved the .dwg files back to AutoCAD 2010 and viewed them on an older i3 PC with an Nvidia Quadro K200 card (1 GB G-RAM) using AutoCAD 2011. There the 3d model appeared correctly for all the shade modes.
I then fitted 2 graphics cards into one PC with 2 monitors and distributed the BricsCAD viewports across 2 monitors.
One monitor driven by 1 channel of an Nvidia GTX 740 "gamers graphics card" with 2 GB G-RAM and the other monitor driven by an Nvidia Quadro K400 "professional" graphics card with 1 GB G-RAM. When the BricsCAD viewport is moved onto the monitor driven by the GTX 740 card then the shaded image is broken. When the BricsCAD viewport is moved onto the monitor driven by the Quadro K400 card then the image is correctly shaded with only front faces visible and it meets user expectations.
I have posted this so that others can learn from my experience. Sometimes the "gaming" graphics cards will do the job, but sometimes they simply cannot cope with the precision processing that "professional" cards can do.
- Richard B