Render like Pixar: Part 3
Unlock the secrets of Pixar's Renderman with VFX artist Rusty Hazelden
Discover how to harness the power of Renderman
For over 30 years Pixar’s Renderman has been used in the film industry to render movies featuring groundbreaking animation and visual effects.
In this four-part tutorial series, we’re going to discover how to harness the power of Renderman by taking an animated shot from start to finish, and learn all of the techniques required to create a photorealistic animation using Pixar’s Renderman for Maya.
Using Renderman to create photorealistic renders has never been easier. In this series we’re going to begin with untextured objects in Maya, and learn how to create surface materials, set up lights, adjust camera attributes, customise the render settings, and batch render the final animation to disk using Local Queue as a series of EXR images. By the end of the project, you will have a solid
understanding of the workflow used to light and render a dramatic night-time scene using Renderman for Maya. Along the way, you will learn numerous tips and tricks that will come in handy on your next Renderman project!
In part three of this tutorial series, we’re going to explore the powerful Alembic workflow in Renderman and find out how to assign materials to Alembic archives using the Dynamic Rules Editor. Once we finish texturing the objects, we’re going to learn how to create a dramatic lighting setup that evokes the feeling of a work light outdoors at night.
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01 OPEN THE MAYA SCENE
Let's continue from where we left off in the previous part. Go ahead and open your Maya scene from the end of part 2. Select the R_nail object in the Outliner. Switch to the Rendering menu set, and from the Lighting/shading menu, select Assign Existing Material>nail_material. This will apply the Nail_material to the R_nail object. The rest of the nails scattered throughout the scene are loaded from an Alembic file.
02 CHECK THE ALEMBIC SETTINGS
Select the Scattered_nails object in the Outliner, and then switch to the Scattered_nailsshape tab in the Attribute Editor. This tab contains many useful settings that will affect how the Alembic file is rendered in Renderman. There are a few important settings that you should always double-check before rendering an Alembic file. Expand the Render Stats section and make sure that Visible in Reflections and Visible in Refractions are both enabled. Then expand the Renderman section and make sure the Render Alembic Cache checkbox is enabled.
03 THE DYNAMIC RULES EDITOR
This Alembic file only contains static nail geometry. That means the nail models that are being loaded from this Alembic file are resting on the ground and not moving. If you have an Alembic file containing animated geometry, you may need to enable the Use Global Time checkbox to load animation data. To assign a material to an Alembic file, we're going to use the Dynamic Rules Editor which can be found in the Renderman shelf. Click on the Dynamic Rules Editor icon to open the editor.
04 CREATE A DYNAMIC RULE
Click the Plus icon in the Dynamic Rules Editor to create a new rule. A rule is used to link a Renderman material in the Maya scene with an object contained in an Alembic archive stored on disk. Alembic archives are a form of file referencing. The Alembic file is read by Renderman at render time, but the actual geometry data is not stored in the Maya scene file. The first text field is for the Material ID, which is also known as the payload. Type in ‘Nail_sg’ and press enter. This is our nail material.
05 INSPECT ALEMBIC ARCHIVES
The next text field is for the rule that will select specific objects contained within the Alembic archive. This is also called the Expression field. The Alembic file contents are listed in the Inspect Alembic section of the Attribute Editor. Double-click on the Scattered_nails entry at the top of the list in the Attribute Editor. Copy this text, and then click on the Expression field in the Dynamic Rules Editor. Type in a forward slash ‘/’ and paste the text ‘Scattered_ Nails’ into the Expression field. Press enter to complete the rule. After modifying a rule you'll need to restart the IPR render to update the Maya Render View. Then close the Dynamic Rules Editor.
06 LIGHT THE SCENE
Let's zoom out a bit in the perspective view, so we can see the whole scene. It's a good idea to use a simple lighting setup during the texture development stage so you have a consistent, bright environment while developing the materials. Now that we've textured the work light it's time to move on to lighting the scene. We're going
to learn how to create a more dramatic lighting environment that evokes the feeling of a work light outdoors at night.
07 DOME LIGHT INTENSITY
The first light we need to adjust is the dome light. Right now it looks like a bright day, so let's start the process of changing this into a night-time environment. Set the Current Time to frame 0 so we are working on the first frame of the animation. In the Maya Render View, let's start an IPR render. Right-click on the IPR Clapboard icon and select the Render_cam. We're going to start by changing the intensity of the dome light to resemble moonlight. Select the Pxrdomelight object in the Outliner, and reduce the Intensity to 0.15 in the Attribute Editor.
08 MOONLIGHTING IN RENDERMAN
The dome light is now darker, which is the first step in creating a convincing moonlight. The next step is to change the colour of the light to make it cooler. We can tint the colour of the dome light using the colour temperature controls. Turn on the Enable Temperature checkbox to display the colour Temperature field. Colour temperature values are measured in Kelvin. Type ‘15000’ in Temperature for a cool-blue tint.
09 ROTATE THE DOME LIGHT
The moonlight looks pretty good at this point. It's darker and has a nice cool-blue tint thanks to the colour temperature adjustment. Since we're going to turn on the light bulb in the next step, let's rotate the moonlight so it provides a rim lighting effect. That means we're going to rotate the moonlight so it lights the side and back of the work light. Click on the Pxrdomelight in the Outliner and then switch to the object's Transform tab in the Attribute Editor. Type ‘-180’ in the Rotate Y field. This will rotate the dome light and provide nice rim lighting.
10 SWITCH IT ON
Now let's turn on the light bulb! Select the Bulb object in the Outliner and click on the
Pixarmeshlight icon in the Renderman shelf. This has created an emissive light source based upon the Bulb geometry. In the Outliner click the plus sign next to the Bulb object and select the Pxrmeshlight to display the mesh light in the Attribute Editor. Switch to the mesh light Shape tab. The mesh light converts the surface of an object into a light source with many of the same controls found on a standard area light.
11 TURN IT UP
Well, the work light bulb is turned on, but it needs to be much brighter. Both Intensity and Exposure can be used to make the light bulb brighter. The Exposure control is easier to work with as the illumination level gets higher. Set the Exposure to 3.5 to increase the light output of the mesh light. The Exposure control provides a traditional photographic way of adjusting light levels in Renderman. This Exposure adjustment would be described as increasing the light level by 3.5 stops.
12 A WARMER LIGHT
To make the light bulb warm, like a traditional tungsten
light source, let's use the colour Temperature control again. Turn on the Enable Temperature checkbox. The default value of 6,500 Kelvin produces cool, white light. Tungsten lights emit warm, yellow light around 3,000 Kelvin. Let's type ‘3000’ in the Temperature field to warm up this light. This looks much better. Now we have cool moonlight in the background with a bit of rim lighting on the reflector and the light bulb is casting warm, yellow light in the foreground, illuminating the nails.
13 CREATE A FILL LIGHT
The front of the work light handle is still a bit dark, so let's create a fill light to brighten up this area in the scene. Renderman provides a wide assortment of lights. Let's create an area light using the Renderman shelf. Rightclick on the Analytic Lights icon in the Renderman shelf, and select the Pxrrectlight menu item. The rectangular area light is created at the origin in the scene.
14 POSITION THE LIGHT
Lights can be easily moved in the Maya Viewport using the standard translation, rotation, and scale manipulators. After experimenting with the placement of the fill light in the scene, let's directly enter the final translation, rotation, and scale values in the Attribute Editor. In the Translate field, type in -8, 22, and 22. Then in the Rotate field, type in -45, -36, and 0. In the Scale field, type in 50, 50, and 25.
15 MATCH COLOUR TEMPERATURE
Adjust the perspective view so the Pxrrectlight is visible. The light is now positioned above the work light and provides extra fill illumination on the cord, handle and nails. Switch to the light's Shape tab in the Attribute Editor to display the lighting controls. Let's adjust the light's colour temperature so it matches the light bulb. It's often a good idea to match the colour temperature of your primary light sources so the lights blend together nicely. Turn on the Enable Temperature checkbox and type ‘3000’ in the Temperature field.
16 REFINE THE INTENSITY
Objects close to lights can sometimes become overexposed.