Motion Graphics by Jeremy Clark

Autodesk Maya

Custom Shaders in Mental Ray and Maya

My “Survival Horror” interior project is quickly becoming an exercise in new lighting techniques in Maya.

I have moved on to experiment with utilizing the Mental Ray renderer’s full funtionality within Maya – not just using it for the final renders of my scenes, but now also using Mental Ray specific Materials, Shaders and Over-rides in the attributes of the objects within my scene.

My first foray into increased Mental Ray implimentation was through using Custom Light and Lens shaders on the lights and cameras in my scene.

Mental Ray Light Shaders

It’s possible to replace the the standard Maya light shaders in a scene with Mental Ray ones. Mental Ray light shaders control light in a way that mimics real world lighting more closely than standard Maya lights.

(Left) A light with standard Maya light shader & (Right) A light source with a Mental Ray custom shader applied. Note the difference in dropoff around the light source.

In order to replace a standard light with a mental ray one:

1.) Open the attributes for any Maya light, and under the Mental Ray > Custom Shaders panels, select to input a new node in the “Light Shaders” box.

2.) With the “Create New Render Node” window open , select Mental Ray Lights > Physical Light.

3.) The original light’s attributes are now overridden by the newly created Mental Ray Light Shader. It is still possible to change the type of light (Spot, Point, Area etc) within the original light’s shape node. To make adjustments to the Mental Ray light’s intensity, dropoff etc, locate the “Physical_Light1” node’s attribute tab.

“Colour” controls both the colour and Intensity of the Mental Ray light. (Intensity set by altering the colour’s “Value” setting.) Increasing the “Threshold” value tightenes the area of darkness surrounding the Mental Ray light. If, for a large scene, an intensity of 1000 is till too dark, you can apply a Mib_Color_Cie_D node into the Colour input of your physical light. This will allow you to overdrive the intensity of the Physical light further.

Mental Ray Lens Shaders

Custom Mental Shaders can also be applied to Cameras to add greater contol to how your Maya scene’s virtual camera interprets light information. To apply a custom Lense Shader:

1.) Select your camera, and in it’s attribues tab go Mental Ray > Custom Shaders. Select to create a new render node next to the “Lesnse Shaders’ box.

2.) From the “Create Render Nodes” window, go Mental Ray Lenses > (Select desired MR Lense Shader).

An example of a useful Mental Ray Lense shader is the Mia_Exposure_Simple node. This node attaches to the camera and offers greater control over exposure, gamma, knee and other settings.

Another is the Mental Ray Bokeh Lens Shader. This is an alternative way to created depth of field in your renders.

This illustrates use of Mental Ray "Bokeh" custom lens shader. The Bokeh shader is a great way of achieving Depth of Field in a render.


Combining Custom Mental RayShaders

It’s also possible to combine custom shaders within a scene. That is, have a custom shader attached to a lens (Lens Shader), and another attached to a Material’s Surface Shader.

For example, by adding a Mental Ray Phsical Light node to a light source, and shine it through a volume that has a Mental Ray Material and Custom Shader Applied, we can achieve the appearance of light passing through “Participating Media”, or airborne particles.

An example of using both custom Mental Ray Light and Material Shaders to render "Participating Media" with a lightsource

One thing worth noting is that volumetric light effects take allot of time to render. For that reason it’s a good idea to utilize render layers, and separate the volumentric effects onto it’s own layer. This way you can isolate it and gain better control, without having to do lots of time consuming renders.

Another example of Volumetric Lighting through the use of Mental Ray Light and Material shaders. Here I rendered the volumetric effects on their own render layer and composited them back into the final image afterwards.


More Indirect Lighting In Maya – Caustics

Within my Film Noir Inspired Lounge scene I also set about learning how to render “Caustics” in Maya and Mental Ray.

“Caustic lighting” generally refers to the patterns of light that are formed when rays of light pass through a transparent material, and are refracted  in a way that patterns appear projected onto surrounding objects. Think of shining a light through a glass of water, and seeing the patterns of light that are produced on the table.

Within Maya, “Caustics” are considered a form of Indirect lighting, as they rely on the use of Global Illumination Photons. For this reason, the workflow for including Caustics in a scene is similar to that of enabling Global Illumination within a render.

Though somewhat straighforward to enable, caustics can be tricky to fine tune, and there are a number of variables that dictate their appearance and quality in a render. Here’s how I implimented them within my scene:

1.) Just like when setting up my Global Illumination lighting, I wanted to keep my Caustic Photon emmitting lights separate from my scene lights. For each light that I wished to appear as if casting the Caustics, I duplicated the light, dropped the cloned light’s “Intensity” to zero, and enabled “Emit Photons” under the new lights “Mental Ray –> Global Illumination and Caustics” attribute editor tab.

2.) Next I jumped into Maya’s “Render Sttings” tab and under the “Indirect Light” tab, I opened the”Caustics” tab and clicked to enable them.

3.) Now came the hard part – fine tuning them to achive a decent enough look. Key settings I tweaked included:

– From the Caustic Light’s shape node Attributes Editor  –> “Mental Ray” –> “Caustic and Global Illumination” dropdown: Photon Intensity (A lower than default value worked well here), “Caustic Photons” (I increaded the number of Photons by 10x the default here), and “Exponent” (I decreased the value from 2.0 to 1.5 here to increase the brightnes of my Caustics patterning.

– Under the “Render Settings” –>”Indirect Lighting” –> “Caustics” tab I set to lower the accuracy from 100 (Default) down to 40. Apparently decreasing the value here is better.

The following depicts two renders of the same lamp, one without , and one with Caustics enabled. Note the patterns formed by the light on the wall behind the glass of the lamp.

This shows a render of one of the lamps in my scene without Caustics enabled.

.. And this is the same lamp, rendered again but with Caustics eneabled.

Though in this scene the effects of Caustics appear somewhat minimal, I still wished to learn about how to use them for a greater understanding of how Indirect lighting works in Maya.

Global Illumination In Maya

My Introduction to Indirect Lighting

Continuing with my Survival-Horror inspired scene in Maya, I’ve started experimenting with different lighting techniques. Having up until this point only utilized simple direct lighting setups to light my scenes, I’ve now moved on to learn more about how to use “Indirect Lighting” to improve the look of my renders.

“Indirect Lighting” occurs when light that is emitted from a direct source (A “Light” in Maya, for example) bounces off of surfaces in the scene. It is from this behavior that this kind of light can also be referred to as “Secondary Light”.

When the light contacts a surface it can take colour from this surface along with it. This newly coloured “secondary” light then lights other objects in our scene.

Global Illumination

The first type of Indirect Lighting that I’ve started to play with in Maya is known as “Global Illumination”. Here light sources are created, and set to “Emit Photons”. These “Photons” travel from the light source and bounce around our scene just like light does in the real world.

It seems that Global Illumination works best if you separate the Direct and Indirect light sources within a scence. Leave the “Direct” lights to provide basic light on objects and cast the scene’s shadows,  and create seperate lights that will emit the Photons required for our Global Illumination.

Therefore we select our “Secondary Light” sources, set their standard “Intensity” to zero (So they do not cast any direct light), but enable “Emit Photons” instead.

Here are two renders of the same scene – one with Global Illumination enabled and one without.

Render withough Global Illumination - Relying only on direct scene lighting.

Render with Global Illumination enabled

Interior Scene – First Render

This is the first moving render of my crime novel inspired Interior. Maya Ncloth was used to animate the curtains and standard particle effects were used for the rain outside the window. Both Polygon and Nurbs modelling techniques were used to construct the elements within the scene.

I plan to add some objects to the exterior and further animate the lighting to enhance atmosphere. This project was my first constructed to scale within Maya, and in truth my first proper interior setting.

The Value of Reference Material

When modelling anything, the importance of visual reference material cannot be understated.

Just like when drawing, there is a temptation to rely soley on our memory to tell us what something should look like. However, if we have an exmple of what we are replicating to work from, our model (or drawing) will be much more accurate.

Proportion, Shape, Colour, Scale and many more attributes greatly benifit from the use of reference imagery. Though it may feel like an interruption to our creative process to do so, it’s great to start any project by amassing a nice stock of real world reference for all the assets in your scene. (A simple Google Images search will usually suffice). This is in fact a really exciting part of the process, as you’re effectively defining the “look” your scene is going to have.

My most recent project called for some antique style furniture. I was surprised by how little I could recall of what defines the appearance of older furniture, though after some quick image searches, I was away laughing.

Here you can see my reference image for a lamp, beside the final model.

...And my table reference alongside the resulting model.

The process of modeling something from reference reminds me allot of drawing from life, in that you are looking, reading, and then reproducing form. Though it may take a little longer, the results are incredibly rewarding.

Meet Me in International Waters? Completed Animation Project – September 2011

Here it is, folks! After months of work, I’ve finished my ocean based animation project. What began as a “You know you’ve made it when..” joke, ended up as a 3 month project. T’is rather uneventful, though one could argue that’s just the point. Enjoy!

Upsize my boat, please.

Along with my experimenting with the Ocean itself, I also set about constructing an oceangoing vessel that would form the main setting for my animation. I started off with modelling what I imagined to be your regular ‘party boat’. This however appeared somewhat lacking in the decadent “International waters party” feeling I was aiming for. I set about turning what was a meagre speedboat into a hedonistic-party worthy mega yacht.

Worth noting is that these renders were taken after basic modelling was completed. Both boats are without texture mapping in each example.