iBooks Author: Best practices for using 3D models
With iBooks Author you can add COLLADA (.dae) files using the 3D widget; learn the best practices for creating these files for use with iBooks Author.
The first-generation iPad is optimized for viewing 3D objects with fewer than 20,000 moderately textured polygons. The second-generation iPad and iPads with a Retina display support viewing 3D objects in a completed book with up to 50,000 moderately textured polygons. More complicated objects may result in an increased load time, slower behavior, or a blurry image.
Use simple lighting with ambient, omni, and directional lights. For best performance, limit the scene to three or four lights.
Any textures you use that are greater than 1024 x 1024 pixels will be resized to 1024 x 1024.
Be sure to add a camera to your object. This will be used for the default view in your iBooks Author book.
A camera can use a perspective projection or an orthographic projection. These are ways of projecting a 3D scene onto a 2D surface.
In a perspective projection, objects close to the camera appear larger, and objects far away from the camera appear smaller. In an orthographic projection, objects appear the same size regardless of how far they are from the camera.
It's best to use a perspective projection in COLLADA (.dae) files you add to iBooks Author, as it mimics the eye's natural perception of the world. Orthographic projections are rarely used.
For more information, see the COLLADA Digital Asset Schema Specification.
Some modeling programs will get better results using the OpenCOLLADA exporters in place of their native exporters. These exporters are available on the OpenCOLLADA download page.
To confirm your 3D object behaves as expected, be sure to preview your book on an iPad before publishing or exporting your book. Try to preview your book on a first-generation iPad to confirm expected behavior for the largest audience.
For more information on the COLLADA format, see the COLLADA Digital Asset & FX Exchange Schema.