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To get started, let's open the Maya scene,
(Where are the tutorial files?) 



Open the scene,, in Maya. For this tutorial we have a teapot spouting particles into the air. In this tutorial we'll cover the basics of using particles with RenderMan for Maya. This tutorial assumes you are familiar with creating particles and Maya Materials using Maya. 


The first thing you'll notice is that RenderMan for Maya renders particles in software rendering. By rendering in software the particles will be correctly anti-aliased, motion blurred, self-shadowing, and fully integrated into the final rendered image. 


Render the Maya scene with RenderMan.  

Render-> Render Current Frame

You should get an image like the one below. Notice how Pixar's Deep Shadows add rich, semi-transparent shadows to the particles:


Particle points rendered in sofware


RenderMan for Maya supports nearly all of the Maya particles. Here are the supported particle types:

MultiPoint — Supported
MultiStreak — Supported
Points — Supported
Spheres — Supported
Sprites — Supported
Streak — Supported
Blobby Surface — Supported
Cloud — Rendered as blobby surfaces
Tube — Partial support 

Particle Cloud Shader — Minimal support

Next we'll take a look at what can be done with several of the particle types in RenderMan for Maya. 




Because we're rendering particles in software mode, we can tweak the Lambert material attached to these particles. We can make the particles brighter by selecting the Lambert and changing its color from grey to white. Note you can adjust any of the Lambert parameters: Diffuse, Transparency, etc. For now just change the color from grey to white, and render the Maya scene: 


You should get an image with brighter particles. 

Brighter particles by changing Lambert's color to white




Motion blur would be a nice effect to add to these particles. We can add motion blur by opening the Render Globals and selecting the Features tab. Enable motion blur by clicking the appropriate check box (next to Motion Blur). Now Render the Maya scene: 

Render-> Render Current Frame

You should get an image like the one below. One of the nice things about Deep Shadows is that the shadows are motion blurred, too.

Motion blur enabled




You'll also notice that RenderMan for Maya honors Maya's per-particle attributes, like color and opacity. This particle system already has per-particle attributes for color and opacity set for you. 


Next add the particle attributes for this specific partical system, points. Do this by selecting the "Current Render Type" button next to the Add Attributes field of the Render Attributes sub-tab. Now we adjust additional attributes for the points particle type. You'll notice that RenderMan renders points in world space, not pixel space, which has the advantage of giving the points an actual size in the Maya scene. We can make the points smaller by setting the Point Size parameter to "1." Now render the Maya scene, you should have smaller points:

Smaller points 


Because RenderMan can handle huge amounts of points, a common technique is to set the points to be nearly transparent and render a much larger amount. So next: change the rate of particles per second from 300 to 30000, set the particles to nearly transparent in the Lambert material, and do the particle run-up again. Now render.

120,275 particle points 




Next we'll work with the Maya sphere particles. Close the scene and then reopen,, to restore the default settings for the scene. 


Now select the particles and change them from points to spheres. Now render the Maya scene; you should get spheres.  

Self-shadowing semi-transparent spheres 

(Rendering time: 114 seconds)


You'll notice that the image took a long time to render. The reason the image takes long to render is the same reason the shadows (particularly the self-shadowing) look good ... the Deep Shadows are storing a lot of transparency data and that gets more expensive the more transparent objects there are. In this case, because there are so many transparent objects, the scene is quite expensive. To speed it up we can get rid of the transparency, so select the particles and delete the per-particle opacity attribute. Now render again ... notice that it renders much faster:

Sphere particles without transparency

(Rendering time: 43 seconds)


It's good to remember that Deep Shadows can create special effects like shadow transparency, but Deep Shadows can also be expensive to render. 



With RenderMan, we can break up the regularity of the spheres by adding displacements to them. To do this, select the Lambert shader attached to the spheres and connect a Solid Fractal as a displacement (from the Lambert's Shading Group node). Now render:


Spheres with a displacement shader


We can now tweak the parameters of the displacement to create a wide variety of effects. For now we'll just set the Alpha Gain of the displacement's Solid Fractal to "-0.5" to push the displacement back in toward the particles. Now render:

Displacement with an Alpha Gain of "-0.5"



Additionally, other Maya Materials can be attached to particle systems. Lambert reads per-particle attributes and should be used in those cases where per-particle attributes are required, but, alternatively, other Materials can be attached to particle systems to create certain kinds of effects (while ignoring per-particle attributes, like color and opacity). To demonstrate this, select the particle system and attach a Maya Ramp Shader. Now render:

Spheres with a Ramp Shader


The spheres are using the Ramp Shader, which means we can create interesting effects, like changing the Ramp Shader's Color Input to Facing Angle and ramping the color from black to green. Go ahead and do just that (the black color should face the camera and the green should face toward the sides). Now Render:

Spheres with Facing Angle


Now we can add another displacement shader. Connect a Solid Fractal to the Ramp Shader, as we did above. Set the Alpha Gain of the displacement's Solid Fractal to "-0.2" to push the displacement back in towards the particles. Now render:

Displacement with an Alpha Gain of "-0.2"



RenderMan for Maya is capable of rendering nearly every Maya particle type and provides advanced features for making particles look as good as possible. Some of the advantages of rendering particles in RenderMan are:

1) Particles are rendered in software ... providing correct anti-aliasing, motion blur, and complete integration. 
2) Rich complex shadows (supporting semi-transparency, motion blur, and self-shadowing) are easy to create using Pixar's Deep Shadows. 
3) RenderMan particle points are highly efficient.
4) Displacement shaders can be added to sphere particles.


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