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Scene format

The scene format is built around the alias/wavefront object with a few extensions for accessing the advanced rendering features offered by polaris

When specifying a path to a material file or other external resource:

  • A relative path (to the current file) can be used
  • An absolute path can be used
  • An http/https URL can be specified to pull the resource from a remote host

Supported commands of the obj format

Command Description
mtllib Import material library
usemtl use material by name
v specify geometry vertex
vn specify normal vertex
vt specify uv coordinate
g specify object group name
o specify object name
f specify triangular or quad face

Specifying the scene camera

The following command extensions can be used to specify the scene camera properties:

Command Description Type Default value Example
camera_fov Field of view Scalar 45 camera_fov 60
camera_eye Eye position Vector 0 0 0 camera_eye 10 0 0
camera_look Camera target Vector 0 0 -1 camera_look 10 -1 0
camera_up World up vector Vector 0 1 0 camera_up 0 1 0

Including objects from external files

Scene files can include other wavefront object files using the call directive. This allows users to break down complex scenes into multiple files or to compose scenes by including pre-defined objects.

The call directive expects one argument for the file to include. For example:

call sphere.obj
call http://github.com/achilleasa/polaris/test.obj

Polaris-specific extensions: mesh instancing

Polaris supports mesh instancing. This allows users to instantiate multiple copies of the same object and associate each copy with a 4x4 transformation matrix. All instances share the same geometry, materials and BVH tree.

A mesh instance can be created using the instance directive:

instance mesh_name tX tY tZ yaw pitch roll sX sY sZ

where:

  • mesh_name is the name of a previously defined group or object.
  • tX, tY, tZ specify the object translation vector in world coordinates.
  • yaw, pitch, roll specify the rotation angles.
  • sX sY sZ specify the object scaling vector. To disable scaling all values must be set to 1.

If no mesh instances are defined, polaris will automatically generate an instance for each defined object using an identity transformation matrix.