Extensions are applied to geometry to change how it is rendered. In some cases, an extension will modify its geometry, while in others, it will replace it entirely. The extensions currently available in this window are:
To create a new extension, right-click and choose the type of extension you wish to create. To assign an extension, select the desired geometry, and use right-click > Assign to Selected, or use the Extensions list found in the Object Properties panel. To edit the parameters for an extension, double-click it to open it in the Extension Editor (shown here editing a Maxwell Grass extension):
The Extension Editor works much like the Material Editor: to edit a given extension, select it in the Extensions list. Following is information about the various extensions.
Maxwell Grass
Maxwell Grass is a modifier – it adds grass blades to assigned geometry. There is not a great deal to say about it here, which is not covered in the main Maxwell Grass documentation.
Maxwell Sea
When an object has a Maxwell Sea extension assigned, it will be replaced in the render with a sea surface generated using Next Limit RealFlow technology. The extent of that sea surface will be determined by the bounding box of the object, so it should generally be assigned to a simple box (and not a plane). Information about its parameters is covered in the main Maxwell Sea documentation.
Maxwell Volumetric
Similar to Maxwell Sea, Maxwell Volumetric replaces its object with a volume containing a simulation of participating media. Also similar to Maxwell Sea, it is the host object's bounding box which will define the volume. If an object has both Maxwell Sea and Maxwell Volumetric extensions assigned, it is the Maxwell Sea extension that will be exported. More information about its actual parameters is covered in the main Maxwell Volumetric documentation.