Rendering

In the last chapter we have set up an environment light – which is great for outdoor scenes or quickly illuminating an object. Three-Point Lighting consists of the Key Light, Fill Light, and Back Light. It refers to situations in reality where several light sources illuminate objects – typically by night, indoors or in situations with bouncing lights. By directing position, intensity, color, shadow behavior of your lightsources you can actually “paint” with light by emphasizing aspects of your model to influence the perception in the spectator. Watch Light & Shadow, an Emmy winning film from director Steve Weiss (20 min) if you want to learn more about the subject. The basic concept of Three-Point Lighting in relation to 3D applications is briefly explained in this Tutorial.

In physical based render engines like Arnold the scene measures refer to real world values. I scaled the displaced terrain from the last chapter to a size of 40000 units (=400 m) which allows me to place a building of  about 7 x 7 and 12 meters on top of the hill. The object I want to see illuminated is called Breather Surface and the building a modified  Menn´s Surface, both are parametric objects created with the free (and still working) Cinema 4D plugins from Jürgen Meier. Create your own building, make sure you cut out enough area for windows.

The typical approach to Three-Point Lighting is to start with a Key Light. In our case we already have the environment light which we can use as the Back Light. With the IPR window open adjust Elevation and Azimuth in the aiPhysicalSky to bring the sun close to the horizon. With the main object selected RMB > Assign New Material > aiStandard Material, increase specularity – because every object in our physical world has some (more or less) specularity. You can find out more about specularity and energy conservation in this introduction to physical based rendering. Move around your camera to find a nice framing with the sun highlighting the edge of the objects from slightly above or the side. The default camera in Maya comes with a focal length of 35 mm which is fine in most cases. I widened the angle to 28 mm for capturing more from the room and to make the image more dynamic. Don’t worry about the noise, we will fix that later in the Render Settings.

With the small Icons “Resolution Gate” and “Gate Mask” above the viewport you can overlay the aspect ratio of your final rendering. Once you are happy with the framing in the viewport go to > View > Create Camera from View.

Lock your new camera by clicking the small lock icon above the viewport. To move around in your scene and to adjust lights switch back to the default working camera at > Panels > Perspective > persp.

Let’s bring in the Key Light, the dominant light source. In the Outliner select the aiSkyDomeLight and hit “H” to hide it for now. Add > Arnold > Lights > Maya Spot Light. Rotate it above and beside to the camera’s viewing axis. For better visibility you can scale the camera and light symbols in the viewport, it does not affect their beavior. Add some color to the Light and increase the intensity to about 100000. The shadow should be softened slightly at > Radius in the Arnold tab of the light.

To soften and extend the illumination provided by the key light and to make more of the subject visible, add a > Arnold > Lights > Area Light to serve as our Fill Light. I rotated it away from the object, that the light bounces back from the wall to soften it. Increase the intensity to compensate the energy loss, in my case about are fine. Adding subtle color makes the light composition look more interesting.

When working with the IPR make sure you leave the settings for exposure and gamma at their default values 0 and 1 as well as View Transform at sRGB gamma. These sliders can be temporarily toggled for diagnosis but must always be switched back by clicking on the icon. The illumination of the scene will be controlled with the intensity of the light sources as well as the brightness and specularity of the materials. Exposure settings can later be adjusted with the camera settings.

The setup from above.

Key Light, Fill Light and Back Light together.

Finally I slightly increased the intensity for all lights proportionally and added specularity inside the building. To reduce the noise I changed > Render Settings > Arnold Renderer > Sampling > Camera (AA) to 8. In the report at the bottom of the IPR window you can see how that increased the render time. For fluent working it is recommended to stay with the default sampling rates, you can even reduce the Camera (AA) Sampling to 1. You only need to increase Camera (AA) Sampling for the final output and quality previews.

Continue with Maya & Arnold Part 4 – Camera / Depth of Field Blur

Every render engine has its own set of lights and materials therefore it is important to pick lights for rendering with Arnold always from the Arnold menu. Add > Arnold > Lights > Skydome Light.

At the Color attribute of the aiSkyDomeLightShape click on the Texture checkerboard icon and in the Create Render Node popup choose the > Arnold > Texture > Environment > aiPhysicalSky. Alternatively you can select the > Maya > 2D Texture > File node and load an external HDR (High Dynamic Range) image. With their higher bit depth (32bit) HDR images are able to capture the lighting information from real world environments which is helpful to illuminate photorealistic scenes. You can downlad free HDR samples from the sibl archive. When you load 32bit HDR images in Maya (.hdr or .exr) make sure to change the Color Space to Raw. Jpeg and everything else should remain at sRGB. Find out more about the new Maya 2017 color management in the Arnold User Guide.

I’m interested in a more artificial look and will continue with the aiPhysicalSky.

Once we have a light in the scene it would render without background:

To add a background go to the Render Settings with the little icon from the shelf. Switch to > Render Using Arnold Renderer. At the tab > Arnold Renderer > Environment click on the Background checkerboard icon and select the aiPhysicalSky.

The aiPhysicalSky node is only available here if you have it created in the previous step with the Skydome Light. If  you have decided to use a HDR image for lighting you can use the same HDR file as background image. Since the background image linked at the Render Settings does not contribute to lighting, you can use any file here (also regular 8 bit jpeg images). The free HDR samples from the sibl archive come mostly with high resolution jpeg images, they should be preferred here.

At the Color attribute of the aiSky node click on the Texture checkerboard icon, in the Create Render Node popup choose the > Maya > 2D Textures > File node and load an external image.

To make the support geometry of the aiSkyDomeLight or aiSky invisible in the viewport you can switch off the LOD Visibility at the Attribute Editor.

Now with the groundplane selected RMB > Assign New Material.

In the popup window select > Arnold > Shader > Surface > aiStandard.

In the Attribute Editor change the diffuse color. Click on the IPR (Interactive Render Preview) button. You might notice a black gap between the terrain and the horizon.

The Physical Sky model renders everything black below a latidude of 0 degrees. To fix it create another Poly Plane with no subdivision, scale it to a value of 10000000 (=100 km) place it slightly below the terrain to avoid intersections and with RMB > Assign Existing Material (the same terrain material). If you have changed geometry in your scene you need to klick on the IPR refresh icon to update it. Other changes in the scene like navigation or shader modifications are automatically updated.

In the aiPhysicalSky node you can influence the lighting and color mood by changing Elevation and Azimuth of the sun. More information about the Physical Sky model with example pictures can be found in the Arnold Manual.

Continue with Maya & Arnold Part 3 –Three-Point Lighting