Background Bitmaps in Rhino

When it comes to placing background bitmps, using the BackgroundBitmap command, bigger is not always better.

Rhino uses OpenGL to display and draw everything you see in a viewport. Image files, or bitmaps, are treated as OpenGL textures. OpenGL has limitations and specific requirements that must be met in order to create textures.

1. The image dimensions must be a power of 2 in both width and height (i.e. 512 x 512, 1024 x 512, 2048 x 4906, etc.).
2. The overall image size must not exceed the limitations imposed by the video hardware and/or video driver. This is video card dependent.

If this criteria is not met, then the image will not display at all.

Because of the above mentioned limitations, Rhino will ensure that all images follow these rules, and thus, in many cases will have to resize and adjust the image accordingly.

If you go into Rhino's Tools→Options→Appearance→OpenGL page you will see what the maximum size a texture can be on your card.

When troubleshooting background bitmap problems, always first make sure you have the latest video driver from the manufacturer of your video card.

If you are having problems display background bitmaps, you might try resizing your image yourself, using your favorite image editing application, so that they meet these criteria. Generally speaking, images sizes of 2048 x 2048 are sufficient and supported my most mid-range video cards.

Keep in mind that just because you can load an image that is 1000000 x 1000000 in resolution does not mean Rhino will use this resolution (for the reasons stated above). You might feel that 2048 x 2048 is too low of a resolution to see the details you want. But, if 2048 x 2048 is your card's limit, then that is the resolution that Rhino will use anyway.