Setting the resolution of bitmap images

Task area Surfaces, Light

Creating bitmaps is equivalent to holding a camera in your hands. In particular, this applies to calculating 3D models in Animation mode, which can be compared to the process of snapping pictures. Saving an animated image is similar to developing photographs. Reality is not displayed to scale.

When you use Render to calculate the front of a 3D box (each side represents 1m) with a render size of 800 x 501 pixels and display the image on screen or print it, you can no longer find out how long the sides of this box are without knowing the real size of the box.

The same applies to photos. The actual size can only be determined if a unit of measurement was visible on the box. Transferring to scale requires references: a conversion unit, i.e. dpi (dots per inch). The output device must always be taken into consideration when you select this conversion unit.

Resolution of bitmap images and print quality

To obtain a good print quality of bitmap images, the resolution is a decisive criteria, i.e. the number of pixels in a specific section. Modern inkjet printers usually print at a resolution of 300 dpi, that is 300 pixels per inch. In other words, about 12 pixels per millimeter. Approximately 3,240 x 2,340 pixels are necessary to produce a bitmap image with a resolution of 300 dpi in the A4 size (approximately 270 x 195 mm; less margin). Enlarging the area considerably increases the number of pixels and disk space required.

Note: Selecting a resolution that is far too high for the printer will not enhance the quality!

Examples of a conversion with 300 dpi

Calculating the resolution

When you save the contents of a viewport of the Animation view type as a bitmap image (= screenshot), the program calculates the number of pixels from the size of the viewport and the resolution of which the monitor is capable. In conjunction with a 24" monitor (16:10), which is recommended for CAD programs, and the viewport set to full screen, this results in approximately 1,916x1,148 pixels.

A printer resolution of 300 dpi leads to the following values:

To achieve a higher quality (e.g. 600 dpi) in printouts, you can reduce the size of the image by half, to 80x48 mm in our example.

If you enlarge the image although a higher number of pixels is not available, the resolution will deteriorate rapidly. For example: In the case of a printout of 50 cm, 1916 pixels result in:
(1916/50) = 38.32 pixels per cm = (38.32*2.5) = 95.8 pixels per inch,
which corresponds to a resolution of 96 dpi.

Rendering with a high resolution

The Render tool can calculate more pixels. To calculate more pixels, you must change the render size accordingly. The maximum render size is 10,000 x 10,000 pixels. The higher the number of pixels, the longer the computing process. To be on the safe side, however, it is advisable to settle for a compromise between number of pixels and computing power in order to avoid pushing the hardware to its limits.

Additional tips:

Producing high-resolution bitmap images