Mental Ray Occlusion Pass Script

Here's another little script that might help some folk. It creates a new renderLayer (or uses an existing renderLayer created by the script) and assigns an occlusion shader as an override.

The shader defaults to output bent normals (in world space) through the output RGB channels, and a 64 sample occlusion pass in the alpha channel. You can change the output, sample rate and light/dark color (defaulting to white and black respectively) by editing the created "btMib_amb_occlusion" node. It's important to note however, that due to occlusion output defaulting to the alpha channel, the light/dark colours have no affect unless you change the output mode.

World-space bent normal pass in output RGB channels.

Ambient occlusion pass in output alpha channel.

The script takes two variables, the first being the name of the occlusion layer (defaulting to "btOcclusionRL" if no name, or an invalid name, is specified) and the second being an array of object(s) to add to the new layer. The easiest way to use the script is to simply select the object(s) you'd like to render in the occlusion layer - groups, transforms and shapes are fine - and then execute:

btCreateOcclusionPass "" `ls -sl`;

This will create a new layer with the default name (btOcclusionRL) and assign all selected objects to it.

Similar results can be achieved via Mental Ray's built-in render pass system, but I find this route beneficial for a number of reasons: Firstly, it's more visually intuitive, giving you immediate scene visualisation, and easy access to occlusion-only renders if needed.  It also separates occlusion from the primary render pass (or passes), allowing an occlusion pass to be farmed out the moment the camera/animation are locked off. While multi-pass EXR's make for tidy folders, they also make for painful re-renders if something needs fixing.

And I just prefer to work via renderLayers where it makes more sense to do so  I hope this proves useful to someone!

Mental Ray Approximation Script

Ignore my strange way of seemingly arbitrarily naming my *.MEL scripts in a way that has only a vague relationship to the procedures contained within. The goal with this naming convention was to package related scripts into a single file. It's not the best way to work, but it keeps my folders clean and tidy. This script only contains a single procedure (as of writing) which assigns a mentalraySubdivApprox node to all selected polygon and subdiv shapes. It's another script which doesn't do a lot other than bypass a bit of a labyrinthine wander through menus (if you suffer from a lobotomy and struggle to recall anything past two turns) but I always prefer one click to 5. Mostly though, the procedure gets used in other scripts that batch process stuff.

boonAssignMRSubdivApprox($approxNodeName, $contents[])

Create (or assign an existing) mentalraySubdivApprox node with the specified name to all of the objects contained in the $contents[] array.

Okay, so it's not exactly voodoo... but who do? You do? Do what? Remind me of the babe!

Maya Render Global Scripts

Here's some more MEL procedures that might be helpful to other folk. There's nothing at all complicated about these, but I use them to reduce the number of clicks I need to do to set up a new scene for Mental Ray. Because I don't like clicking. It bothers me. Enough that I am happy to spend hours coding to save several seconds of clicking. I'm weird like that.

 boonSetRendererToMentalRay;

Checks if the MentalRay plugin is loaded (and loads it if it isn't) and then sets common MentalRay render globals, including: enabling color management and linear workflow, checking that the OpenEXR plugin is loaded, setting default output options, framebuffer to 32bit float, render mode to raytrace, and disables the default light.

 boonSetRenderOutputString($passType);

Sets the renderer output string to either multi-pass EXR ($passType = "Combined") or per-pass EXRs ($passType = "Separate").

boonSetRenderQuality($qualityPreset);

Sets some of the render globals relating to render quality, allowing you to quickly toggle between Draft ($qualityPreset = "Draft") and Production ($qualityPreset = "Production") settings. These presets are different to the default preset list available in render globals, and can easily be edited for preferred workflows.

boonSetRenderResolution($resolution);

Not much to it. Sets the render resolution to either 'Half' HD720 ($resolution = "HalfHD720"), HD720 ($resolution = "HD720") or HD1080 ($resolution = "HD1080). Essentially, the epitome of laziness.

Download these scripts and enjoy saving yourself about 4.5 seconds per scene.

Mental Ray Matte Pass Creator

A little off the topic of gameDev, but I've been working on making myself employable again lately, and that means diving back into Maya. I've been playing around with MentalRay, and I decided to write myself some MEL tools to help with setting up MR render properties and passes. This first tool assists with setting up matte passes, which are kind of fiddly and annoying to set up by hand - particularly if you have a large number of mattes to create. My tool sets the mattes up as single-channel, 8-bit render passes which are ideal for multi-channel EXR output.

Installation

Extract the contents of the .zip file into your user scripts directory, and then navigate to "yourScriptDirectory/MEL/boonTools/helper/boonHelper.mel" and edit the global variable $boonToolsRoot to point to your root script folder.

Launch the GUI with the following code:

source "MEL/boonTools/Render/boonMRRenderPassMatte.mel"; boonMRMattePassGUI();

Instructions

The following is the boonMRMattePass GUI:

Matte Layer: Select either <New> layer, or an existing layer on which to apply a matte pass and create pass contribution maps.

Layer Name: When the <New> option is selected, this defines the new layer's name. If you type the name of an existing layer, the tool will behave the same as selecting that layer from the Matte Layer menu.

Matte PCM: Displays any pass contribution map assigned to the layer selected in the Matte Layer menu. If you select an existing PCM, selected objects will be added to it rather than a new matte being created.

Group Mode: When creating new pass contribution maps, this determines how the PCM(s) are created. Single creates one PCM containing all selected objects. Selection creates a unique PCM for each object/group in the current selection. Selection & Children creates a unique PCM for every individual object in the selected hierarchy. NOTE: If more than 10 PCMs will be created, you will be prompted to confirm.

Single / Suffix: When <New> is selected in the PCM menu, this defines the name for a Single PCM or the suffix for multiple PCMs. A suffix MUST be specified to ensure that PCMs created for multiple objects do not share the object's name. Note that if a name for a PCM which already exists is supplied, that existing PCM will be added to the membership of the specified layer.

Layer Suffix: If true, the layer name is also suffixed to the end of the PCM/matte renderPass. This is just to assist with unique naming if necessary, but is disabled by default.

Output PCM / Output Pass: Displays previews of the output PCM / matte renderPass names.

The recommended workflow with boonMRMattePass is to create a specific matte renderLayer, assign all geometry to the layer (no lights or unnecessary nodes) and then create matte passes for objects/groups as needed. Keep in mind that to create a holdout where non-matte geometry is occluding matte geometry, all occluding geometry must be added to the layer. If you're not dealing with transparencies, you can easily maximise rendering performance on the matte layer by assigning a simple surface shader as a material override.

I hope this comes in handy for someone. I imagine I'll be writing more render assistant tools over the coming days (the next plan is an ambient occlusion pass including bent normals for diffusely-convolved environment lookup). Also, coding in MEL makes me so, so happy... that Unity and C# are NOTHING LIKE IT.