Maya Station

Where to Start When Creating a Custom mental ray Shaders for Maya

Where did January go? I feel like it was only January 1st last week. It’s one of those rainy-snowy weeks in Toronto, which is kind of miserable if you ask me.

However this is a momentous week, as I did get to meet my blog mates Annick and Owen, you might be thinking “WHAT?!? You’re on a blog together…..” Autodesk is very global, and we are based out of different offices, and it’s not that we don’t regularly communicate, it just this is the first face to face meeting, so now I have a face for the name :)

I was digging in the crates (or rather my computer file folders), and I found some notes I made a while back on shader writing from a mental images training and I thought I would share them with you.

Writing Shaders:

This is an introduction to writing mental ray shaders; we want to try to follow these steps, to compile a shader that will run inside mental ray for Maya.

Unwanted blur over image plane with DOF

Once you enable Depth of field on your camera and render with mental ray. The image plane will be effected with the blur effect
You can overcome this number of ways, one of which is using the Bokeh lens Shader rather than the default Depth of Field of the camera

Spikes in the 32 bit renders with HDRI

Files containing  mia_material and HDRI rendering might produce spikes in the reflection when switching to 32 bit floating point
The following is the render with 8 bit and when switching to 32 you see the “un-smoothed” reflection.

 
this is a natural result of HDR rendering. 
A sub-sample intensity spike will light-up a pixel and not its neighbors, which may look like poor filtering, but it is really just a limitation of the camera model. 
Some advanced lens Shaders will solve the problem by clamping or damping color values downstream of the exposure control (or other tone mapping), but before filtering, resulting a higher quality and visually pleasing output.
I used the mia_exposure_simple and dropped the gamma to 1.00 (to match the render) this improves the render and helps eliminate these spikes.

Thanks to Turner Studios for providing us with the scene file

Note: you can also use mib_lens_clamp

Watch attribute values in the HUD

Have you ever found yourself writing an expression that prints out attribute values so you can analyse the behaviour of a node? Then I don't need to tell you that this kind of expression time is time-consuming to write, while printing to the Script Editor slows performance considerably.

Of course you could keyframe your attributes and manually step through the timeline frame by frame to force a refresh of the Channel Box and look for your attributes values there, but the drawback is that the Channel Box only displays one node at a time.

Instead, here is a method that uses the HUD to query and display attribute values when you're working interactively, or during the playback of your animation.

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Autodesk Maya Tips & Tricks Today!

Join us today for Autodesk Media & Entertainment Webcasts  - Maya Tips & Tricks - January 14

http://www.resources.autodesk.com/med/Webcasts

exporting with FBX

When exporting a character rig using the latest version of the FBX plug-in, it is important that none of the geometry is assigned to a mental ray shader. If so, this will cause Maya to crash.

 

Make sure all the geometry is assigned to Maya shaders first before exporting.

 

Autodesk has placed this product issue on development's product modification schedule.

Maya Fluid Effects Dvd now online

Link

Thanks Duncan

BackBurner 2010.2 for MacOSX

Autodesk Backburner 2010.2 for Maya 2010 extends Backburner functionality to support network rendering on the Mac OS X platform. Previously network rendering was supported on Linux and Windows only. Network rendering allows animation scenes to be rendered by many computers working collectively on the same network. In addition, the extension introduces a new version of the Backburner Web Monitor. The new Backburner Web Monitor is a full-featured, desktop-like application that runs entirely inside a web browser. It is an Adobe Flash Player compatible application that replaces the older html-based Backburner Web Monitor, no longer available as of Backburner 2010.2

Note: you need 10.6 and up

http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=14300386&linkID=9242259

remove reference edits

 If you have made changes to your reference file which has then caused incorrect results, For example making changes to an expression then saving the reference file causes you to lose your expression information; simply reloading the reference file will not be enough to get the original data back.  

You will need to remove the wrong edits.   In order to do this you need to unload your reference from the Reference Editor, and then go to Reference Editor ->List Reference Edits.   In the window that pops up select the wrong edits and click on Remove Selected Edits.  Once this is done you can Reload you reference, through the reference editor.