Upgrading from mental ray 3.4 to 3.5
What's new in Version 3.5
Scene Description Language
Shader Writing and Integration
Incompatible Changes

What's new in Version 3.5

Here is a summary of some of the new features and feature improvements in version 3.5 of mental ray:

New final gathering modes

mental ray now has four final gathering modes: "automatic", "multiframe", "3.4", and "strict 3.4". The automatic and multiframe modes have been greatly simplified and do not require control by radii, while usually giving superious image quality. The multiframe mode is specifically designed to avoid flickering artifacts in camera animations. The 3.4 and strict 3.4 modes are provided for backwards compatibility.

Light lists in instances

Light lists have been added to geometric instances to offer a general, more flexible ways to specify lights for illumination, and for finer control over shadow casting. The same material may now use different lights on different geometries. Light lists provide a new, standard method to pass lights to shaders for illumination; they require, however, support in the shaders by using the new light iterators.

Catmull-Clark meshes

Catmull-Clark polygon meshes ("ccmeshes") have been introduced. This subdivision surface type uses Catmull-Clark rules for smoothening and supports polygons with arbitrary numbers of vertices.

Reloading of .mi files for reduced memory consumption

A command line option -reload has been introduced. If this is specified then mental ray attempts to avoid keeping geometric objects read from the mi file in memory permanently, but re-read them from disk as needed. This optimization is not applicable to all scenes and workflows but may save large amounts of memory on certain complex scenes.

Per-face data

Per-face data have been introduced for polygonal geometric objects. Per-face data make it possible to attach arbitrary floating point data to the primitives. An object may also contain per-primitive data information to identify the data attached to the primitives.

String options

Up to version 3.4, options are hardcoded in the .mi syntax and options data structures. It is now also possible to add new string options in a more extensible way as arbitrary name - value pairs, where the name of the option is an arbitrary string, and the value can be of any of a few basic types.

Photon merging

A new, optional optimization of global illumination using photon mapping called photon merging has been implemented. This feature reduces memory consumption in scenes with complex indirect illumination where were many photons must be shot but only few of them contribute to the rendered image, by merging photons in memory which are closer to each other than a user specified distance threshold. Some scenes which previously could not be rendered in sufficient quality due to memory size of the shot photons may be rendered now using this option.

Built-in shaders

As of version 3.5, mental ray has a small set of simple built-in shaders. These are intended for simple visualizations, where speed and simplicity of scene setup are more important than customization of shading elements. The shaders are designed to be flexible, but to offer only little control over shading details.

Paint shader library

A paint shader library has been added with shaders for metallic paint.

Other improvements

Scene Description Language

The following changes were made in the .mi scene description syntax:

Shader Writing and Integration

The following changes were made in the shader and integration interfaces.

Note: All shaders and integrations should be recompiled for mental ray version 3.5. Many data structures in the shader interface and integration API have been changed. Shaders compiled for an earlier version of mental ray may crash without error indication if they access changed data structures in the shader interface.

Incompatible Changes

The following changes were made in mental ray 3.5 which are not backwards compatible or which may cause different results than previous versions of mental ray:

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