Fix For Out of Memory Errors Due To Large Image Files

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With raster images being used much more commonly than in the past, I wanted to address some of the possible reasons a user may have trouble with the plotting of these images.  We are going to discuss 3 places to look when you have problems, and which order to start your troubleshooting:

  • RASTERPERCENT Variable
  • RASTERTHRESHOLD Variable
  • Raster Slider Bar

raster_variables Beginning in AutoCAD 2007, two new variables were added to help manage how much of the available system resources AutoCAD uses when plotting raster objects: RASTERPERCENT and RASTERTHRESHOLD. (Note: Neither of these variables are noted in the AutoCAD 2007 nor 2008 help files, but were included in the product read me files).  Both of these variables are accessed by typing at the command line.  Keep in mind these are system variables and will apply to all drawings.

The RASTERPERCENT variable controls what percentage of available system resources (in other words: virtual memory) can be used to calculate raster output. Previous to this variable, AutoCAD would use all available virtual memory and had the potential to affect the performance of other applications. The default setting is 20, which means that AutoCAD can only use 20% of available virtual memory. While this setting is fine for most drawings, this may not be enough memory for more complex drawings which can result in incomplete drawings, hangs, lock-ups, or crashes when plotting. The higher the setting, the slower other applications could run while plotting in AutoCAD.

The RASTERTHRESHOLD variable limits the size that the “plot file” can be. By default it is set to 20 megabytes. This means that if the calculated “plot file” would exceed 20 megabytes the plot will be aborted. Before AutoCAD 2007, instead of the plot being aborted, crashes or incomplete plots could occur. A higher setting may be necessary for complex drawings or drawings with large or many raster images attached.

The third setting that can impact the size of these plots is the Raster Images control in the Plotter Configuration Editor. Depending on the device you are using, the PC3 file may have the ability to manage “how much” raster data is sent. One way this setting can be set is when plotting:

  1. PLOT (or Page Setup Manager)
  2. Select your plot device
  3. Click on the Properties… button to open a Plotter Configuration Editor dialog
  4. On the Device and Document Settings tab, expand the Graphics node
  5. Highlight Raster Graphics (if available)… the slider bar that controls the Raster and Shaded/Rendered Viewport quality can be found in the lower portion of the dialog

raster_slider Previously to AutoCAD 2008, the default setting tended to be with the slider set in the middle. Currently, with some drivers, the slider is defaulting to “Best” which means that AutoCAD is sending a lot more data than was probably sent using prior releases of AutoCAD. If the slider is set all the way to the left (“None”) then drawings will plot with no raster images or shading at all.

Please note that note that this slider bar is not available for all plotters.  In fact, some plotters may have a different or similar took for changing this.

The following are suggestions to help you discover the optimum setting for your configuration.  Keep in mind that this configuration could change depending on the size of the drawing, attachment, how the Visual Style is configured, the driver and/or the plot device, etc.

Step 1:

  • Set RASTERPERCENT to 90
  • Set RASTERTHRESHOLD to100
  • Set the Raster slider bar one notch above None

Step 2:

  • If the above works, try the Raster slider bar up a notch to the right.  Keep testing until you hit the limit.

Step 3:

  • If the above works, decrease RASTERTHRESHOLD incrementally by 10-20 megs between test plots until the default value (20) is reached, or plot performance is negatively affected

Step 4: Once you find the optimum setting for RASTERTHRESHOLD:

  • If performance of other applications does not seem to be negatively affected when plotting from AutoCAD, you can leave RASTERPERCENT set at 90
  • If system performance is impacted when plotting from AutoCAD decrease RASTERPERECENT incrementally by 10-20 percent until an optimum level is found
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