Render Photo-Real HDR Images in Maya and Pixar’s RenderMan

By Nino Del Padre Source: Studio Monthly

The acronym HDRI stands for High Dynamic Range Image. There are many commercial sources to purchase all types of HDRIs. However, there are a few free ones floating around the net. A great place to learn more about HDRI is Paul Debevec’s site. He has several HDRI images available for download. Go to www.debevec.org/Probes/ and download a few of the Light Probe Images in the.hdr format. The Uffizi Gallery, for instance, is a good one to experiment with. You can also download a free evaluation copy of RenderMan for Maya at Pixar’s site at renderman.pixar.com/ if you don’t own it.

STEP 1: Download a few HDRI images
STEP 2: Create a new Maya project and choose RenderMan as the renderer

Open the Plug-in Manager: Window> Settings/Preferences> Plug-in Manager and find the RenderMan for Maya plug-in. Check loaded. This will load RenderMan for Maya. Close the Plug-in Manager and Click Window > Rendering Editors > Render Settings. Choose RenderMan from the Render Using drop-down menu. Choose a resolution of 640 x 712 and under render options uncheck Enable Default Light.

 

STEP 3: Create a ground plane and import your model

 

Create a ground plane, click the Create > NURBS Primitives > Plane Options box. Set the Axis to Y and 100 for both the width and length and click Create. Select the NURBS plane and choose Lighting/Shading > Assign New Material> Lambert. Click on the color box and choose a tan color as shown. Import your model or create a primitive shape and assign a Blinn material to it. Use the keyboard shortcut 6 to display the smooth shaded view.

 

 

 

STEP 4: Set up your render global settings and create a Renderman ENV light

 

Open the render Globals, and in the Common tab switch to the Features tab and enable the Ray Tracing check box. Click on the Motion Blur check box and change the motion factor to 0. Next, uncheck the Motion Blur box. Change the trace Bias to.050 and change the Max Specular Depth to 4. Under Global Illumination create an Environment Light.

In the Environment Light Attributes, click on the folder icon next to Environment Image and choose one of the HDR images you downloaded. I’m using the Apt-probe.hdr image for my render. Change the sampling mode from filtered to sampled, increase the number of samples from 64 to 300 and the max variation from 10 to 1. Now we can see that a RenderMan Environment Light has been added to the Maya scene. The RenderMan Env Light is a master control to anything related to Global Illumination in RenderMan for Maya.

 

 

STEP 5: Frame your shot and enable depth of field

 

Select the View > Camera Settings > Resolution Gate. This will help you position the camera. Move the camera to frame your shot. As most of you know, depth of field is the amount of distance between the nearest and farthest objects that appear in acceptably sharp focus in a photograph. It’s one of the more important elements in making CG images look photo-real. One of RenderMan’s many strengths is its high-quality depth of field. Create a locator to use as your focal point as we’ll be using a shallow depth of field. Go to Create > Locator and position in the area you want to be in focus. In this case, I want the words "Del Padre" to be the focus point.

Turn on Display > Heads Up Display > Object Details. Now select your locator and make note of its distance from Camera. In this case, it has a value of 35.661. Now enable Depth of Field, choose View > Select Camera, expand the arrow next to Depth of Field and click the check box. In the focus distance, use your locators distance from camera 35.661, leave the F Stop at 5 and leave the focus scale at 1.

 

 

 

STEP 6: Set the render quality

 

For RenderMan, Pixel Samples is the most important quality setting for depth of field. You can increase Pixel Samples by opening the Render Globals and selecting the Quality tab. Increase the Pixel Samples to 11 x 11 (which will cause RenderMan to sample each pixel many more times). Shading Rate is the main global quality control for Pixar’s RenderMan. Set the Shading Rate to 1, which is a typical Shading Rate for final rendering. Test renderings can usually be done at 3.0, 5.0 or even 20.0.

 

STEP 7: Render time

 

Choose Render> Render Current Frame and wait. It could take a while with our high-quality setting, depending on your workstation. It took 45 minutes to render on my BOXX 7400 series workstation with Dual AMD Opteron dual-core processors and 4 gigs of RAM.

YOUR GUIDE

Nino Del Padre President/Founder Del Padre Visual Productions, Inc.

Founded in 1991, Del Padre Visual Productions’ work is inspired by the greatest achievements of the cinematic arts. Specializing in Flash Web site design, HD video production, motion graphics, 3D animation and interactive CD-ROM applications for companies such as LEGO America, BAE Systems, NASA and many others, DVP’s work has earned extensive industry acclaim.

Nino Says Keep in Mind...

Using Pixar RenderMan’s global illumination techniques inside Maya lets you create highly realistic lighting with minimal setup. You can achieve drastically different looks by simply rotating the RenderMan Environment Light and trying different HDR images. You can also try changing the Environment Light Shadowing attributes to Color Bleeding and experimenting with different shadow bias, gain and light intensity.

Del Padre Visual Productions, Inc. www.delpadre.com 15 Benton Drive East Longmeadow, MA 01028 ph. 866.792.3282 nino@delpadre.com

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