Setting Up the Skydome Background
Open the Hypershade window
Create an Arnold > Texture > Environment > aiSky. Zoom (Alt RMB) or move (Alt MMB) the node view to see the newly created node.
Within the Hypershade window Create > Maya > 2D Textures > File. Drag a connection from the Out Color of the file node to the Color input of the aiSky node.
Select the file node and connect the previously downloaded panorama file (…Bg.jpg or …Ref.hdr) with the folder icon at Image Name.
Click the Render Settings Icon on the toolshelf
Go to the Arnold Renderer tab in the Render Settings and select the newly created aiSky from the Background pop up menu.
In the Windows > Outliner a new Object named “transform1” appears, the transform node belonging to our aiSky. We rename it “aiBackground” to know what it’s good for. To stay organized in the Outliner elements can be reorganized by dragging them with the MMB.
The aiSky should only contribute to the background while the SkydomeLight we added in the previous tutorial is responsible for lighting and glossieness of the scene. By default our background aiSky would contribute to lighting and glossieness too and generate overexposure. So let’s switch unnecessary channels off. With “aiBackground” selected we go to the Attribute Editor and deactivate everything in the Render Stats of the aiSky except “Primary Visibility” and “Visible in Refractions”. That means the aiSky is solely responsible for showing the background image – also through refractive (transparent) materials. The other components Shadows, Glossy, etc. already come from the SkydomeLight.
Activate the IPR.
Now the HDR background shows up the exposure should look well balanced.
The noise on the ground can be reduced by increasing the number of samples of the aiSkyDomeLight. Be careful, raising the samples too high increases also render time.
Now more light samples per pixel are emitted resulting in less noise at areas directly lit by the SkyDomeLight.
The black part inside the torus means: here are no glossieness calculated from the opposite side. That can be fixed by increasing the Glossy Ray Depth in the Render Settings. A value of 4 is fine for our purpose, keep in mind that raising the Ray Depth values also slows down the render speed. You only need to increase that value if you want to see glossy objects reflected in other objects (a glass facade reflected in water and vice versa for instance).
Rendering with higher Glossy depth.