3D to 2D: Getting Images out of CAD Software

SU Export: 400px wideA comment on one of my SketchUp posts prompted me to provide clarification in the form of a new post rather than just a quick reply. The issue was that exported images from CAD files (SU in this case) can be quite grainy.

To export an image of the current view in SketchUp, go to File > Export > 2D Graphic… and select a file format for the export. In the save dialog that opens, there is an option button that allows for customizing. That’s where you want to make the following adjustments:

If you export to a raster format like JPG, BMP or TIF, select a large image size. In most cases, something around 2000px width will give good results. In any case, use a larger image size than you want to produce. If you plan on producing a poster, go very large. The upper limit for this size seems to be set by your computer’s processing powers.

After exporting the files, you can then resize them to the final dimensions taking advantage of nice antialiasing. The following images show the difference between exporting to a low and a high resolution:

SU Export: 400px wide

SU Export: 1600px wide

Keep in mind that the larger you go (and the less grainy your images get), the smaller all edges will get since their width is defined in pixels. You might thus have to adjust line width before exporting (do this in SU’s Styles window).

If you export to a vector format like EPS, PDF or DWG, line width is usually not as much of a problem since lines are defined parametrically and rendered in your imaging software (Photoshop or whichever you are using). Make width and size adjustments there. The image below is from an EPS export:

SU Export: EPS

All of this holds true for other CAD software as well. For example, in AutoCAD, select “DWG to JPG” as printer in the print settings and set the image size to something quite large. Again, if you need wider lines, adjust line width before you export.

One caveat: When you export CAD views to a raster format, you lose all dimension information. Lengths that used to be stored internally as a 16-digit number, now measure X pixels. Even with a length reference, it is impossible to again scale these images to the same precision. If you need less precision and are happy with a reference length in your images, don’t forget to include a scale (at least an object of known length) before you export the views.

The following images illustrate the difference between a raster and a vector representation of a line:

Raster Line

Raster Line (defined by pixels)

Vector Line

Vector Line (defined by 2 points)

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