Celestia/3D Models

Introduction

In addition to its internally defined spherical objects, Celestia can use 3D models to display bodies with complicated shapes.

Usage in Celestia

A 3D model will be displayed when Celestia encounters the Mesh directive in one of its catalog files. For example,

Mesh "file.3ds"

If a Texture declaration is included in the entry for the same object, that texture image will replace all diffuse material texture images specified in the model file.

Model Types

Celestia can display three different types of 3D model files.

3DS

Originally developed by the authors of 3D Studio Max, the .3DS binary file format is used by many different software packages. Model files usually can be created in this format by choosing it in the "Export" menu of your favorite 3D modeling program.

CMS

CMS Model Files are unique to Celestia. They use a simple textual format. The CMS format is deprecated.

CMOD

CMOD Model Files are unique to Celestia. They have both binary and textual forms. The format was designed for efficient use by OpenGL code. When drawing a CMOD model, Celestia's framerate is about 1.5-2x as fast as when drawing the equivalent 3DS model.

A 3DS to CMOD conversion program is available. CMOD export scripts are available for Anim8or and Blender.

Modeling Programs

• Blender 3D - this is an open-source, free software that is extremely powerful. However, it is quite intimidating to use for beginners. Blender 3D: Noob to Pro is a Wikibook that has good guides to help you, if needed. Note: as of version 2.80, Blender no longer supports exporting 3DS models.
• Anim8or - free modelling software. This is only available for Windows, however.

Limitations

1. 3DS models have a limit of 65536 vertices and polygons, making extremely high-resolution models impossible. This limitation, however, does not exist for CMOD models.
2. Models in Celestia do not (yet?) cast shadows on themselves or on other objects.
3. Translucent model surfaces are not properly depth sorted. Some are drawn correctly, but some are not.
4. DSC Nebula Meshes are not depth sorted at all. They always are drawn in the order that Celestia reads them.