Requirements To 3D Models

This article describes the recommended methods of importing 3D geometry (3D models) to UNIGINE by means of UnigineEditor.

The FBX file format is recommended for working with 3D geometry. Export to *.fbx is supported by the most popular 3D editors: Autodesk Maya, Autodesk 3ds Max, Blender, Modo, etc.

After importing the *.fbx file into UNIGINE, a so-called runtime file is generated in an internal MESH file format for the source file. The created *.mesh file is saved to the data/.runtimes folder created in the same directory as the source *.fbx file in the data root folder.

In terms of UnigineEditor, the imported file becomes an Asset, a "unit of work" used in world building. After the asset is added to the virtual world, its geometry (same as any object in the scene) becomes the node and can be seen in the World Hierarchy window. Any material, assigned to this geometry, becomes the single surface of this node (surfaces can be found in the Surfaces section on the Node tab of the Parameters window).

The mesh limitations set in UNIGINE:

For example, in the 3D editor we have the car model consisting of five parts (the frame and four wheels). Two materials (car paint and glass) are assigned to the frame, one material (rubber) is assigned to each wheel. After the model has been exported to *.fbx and then imported to UNIGINE, five *.mesh files will be created (according to the amount of car parts in the 3D editor):

• Each of the four wheels will have one surface, as one material has been assigned.
• The frame will have two surfaces (as two materials have been assigned).
• The names of the surfaces will correspond to the names of materials assigned in the 3D editor.
• UNIGINE materials will be created automatically on the *.fbx file import; their names will also correspond to the names of the 3D editor materials.

UNIGINE supports two UV channels for geometry. To specify whether to use the first or the second channel, use materials settings. For example, you can use the first channel for tiling, and the second channel for the light map.

If you want to create several variations of one object with different levels of detail (LOD), it is recommended to create them as individual surfaces. This will allow you to reduce the amount of nodes in the hierarchy and simplify the settings of the LODs visibility. The amount of polygons in the neighbouring LODs should differ at least 2-3 times. The recommended amount of LODs is 2 or 3 (more LODs will cause big CPU load).

To import LODs (different objects) to UNIGINE as different surfaces of one node, choose the Combine by Postfixes option on FBX import.

UNIGINE supports the most popular bitmap texture formats: *.png, *.jpg, *.tiff, *.dds, *.tga, *.rgb, *.rgba, *.psd, *.hdr, *.pgm, *.ppm, *.sgi with support for:

• 8, 16 and 32 bit precision per channel
• Alpha channel
• Baked MIP-levels

You can import texture of any type listed above: the runtime *.texture file will be generated automatically, if necessary.

Texture resolution should be power of two, for example: 128×128, 256×256, 512×512, 1024×1024, 2048×2048, etc. Both square and rectangular textures are supported (for example, 256×1024 pixels).

Texture resolution should not exceed 16384×16384.

The texture postfix is important as it defines the compression algorithms and used color channels. For example, the postfix _alb is for albedo textures, _n and _nrgb for normal textures, etc. The full list of postfixes is available here.

UNIGINE supports skinned mesh animation (3D model vertices have corresponding bones and their weights). The animated 3D model should be divided into two objects — Mesh and MeshAnimation:

• *.mesh contains bind pose and geometry (surfaces with data on weights for all vertices).
• *.anim contains bind pose and animation frames for bones.

To export animation to *.fbx from 3D editor choose Animation and Bake Animation and specify which frames should be exported. When importing the animated *.fbx file to UNIGINE, separate *.mesh (containing geometry) and *.anim (containing animation) files will be created.

The limitations set in UNIGINE:

• Maximum amount of weights per vertex: 4

For file and surface names it is recommended to use English, lower case, without spaces.

• Mesh class API
• MeshAnimation class API
• Article on Mesh File Formats