Autodesk Product Manager Doug Look works with customers who use DWF Composer for digital measurement. Many of these customers asked how to determine the appropriate DPI to get appropriate levels of precision in their DWF files. They wanted to ensure a certain number of significant digits in the readouts provided by Autodesk DWF Composer.
As such, Eric Haines, one of our Lead Software Engineers on DWF Composer, devised a formula for determining appropriate DPI settings that AutoCAD or other authors can use to get appropriate dimensions. The variables included: DPI, precision level, virtual paper size inside the DWF, and actual size of print out. The easiest way to express this formula is in a table of popular values. “Measurement per inch” is listed across the top. “Precision desired” is listed along the left. The table contains the results which are the DPI values that an AutoCAD user would want:
So as an example, if you had a drawing where 1 inch equals 10 feet and wanted to use DWF Composer to measure to the nearest 1/8th of an inch, you would generate the DWF file using a DPI value of 1920. You can specify the DPI in AutoCAD by:
1. From the menu, select File->Plot. This brings up the Plot dialog.
2. Ensure that DWF 6 ePlot.pc3 is selected. Click on Properties. This brings up a tree control.
3. Select “Graphics” from the tree and expand it. It contains an entry for “Custom Properties.” Select “Custom Properties” in the tree control. This displays a Custom Properties button. Click the Custom Properties button.
4. Set the “Vector resolution” to the desired value. You can leave the other DPI values (i.e., “Gradient resolution,” “Color and grayscale resolution,” and “Black and white resolution” as they are. Legal values from the menu pull down are between 150 and 4800. A custom value, such as 30270, can be entered using the keyboard.