Illuminate a scene with a spherical panorama.
- In this chapter, we'll explore techniques for natural and environmental lighting. The primary tool for that is the Arnold Skydome light. It provides environmental illumination that can be mapped with a high dynamic range image. This is the preferred method of image based lighting in Arnold. Material emission, the Arnold mesh light, and the AI sky environment can also provide a form of IBL, but they are not optimized for that purpose.
The skydome light produces much less grainy results at lower sample rates. Let's get a rendering of this stylized outdoor scene with focus on the camera view. Go into the menus and choose Arnold, render. The Arnold render view opens up, but we have a black screen because no lights have been added to the scene yet. Go back into the menus and choose Arnold, lights, skydome light.
A sphere appears at the origin, and that's the AI skydome object. And now we see illumination in our Arnold render view. The skydome provides illumination in all of the render components, such as diffuse, specular, and transmission. Let's look at the attributes for the AI skydome. With it still selected, open the attribute editor with control, A. And of course we have the usual color intensity and exposure. We can lower the exposure to dim that light or increase the exposure to increase it.
Set it back to zero. We've also got the samples here which is the visual quality. Let's take a closer look at this in the Arnold render view. Go over there and grab the crop region tool. Click on that, and then click and drag on a grainy area in the lower right of the frame and release the mouse and now only that area is being rendered. Let's zoom in on that, you can do that with the mouse wheel and the Alt and middle mouse button.
Get that framed up so that we can see the grain quite clearly. In the attributes change the samples value to five. And now you can see that it's less grainy inside that square than outside. We can exit out of the crop region tool and go back one to one real size in the render view. Now let's map the skydome with an HDRI image. Up at the top of the attributes, in the color attribute, click on create render node.
In the create render node dialogue click on file. Back in the attribute editor, we now see the file node. Let's rename the node. Call it skydome file and press enter. We don't need the filter here so let's turn filtration off. And we're ready to assign the actual image. Click on the browse button and in the current project source images, select the file lofi sky V2 4K by 2K .exr.
And click open. The bit map might take a moment to load on your system as it's converted to a .tx file. We'll talk more about that in the chapter on materials. I just want to point out that it is an EXR document, and Mia has directly interpreted that as having a raw color space. We've got illumination and shadows in our render view, we also have a background of a lofi sky. The view port doesn't match the Arnold render view.
Let's grab the move tool, and move the skydome in the top view and as we move it around we see that the background doesn't change and the lighting doesn't change. So position is not important for the purposes of the render view. But rotation does count towards the rendering. So let's go to the skydome light, transform mode, and we got rotation in Y, we just type in a value there of 180, and now we're seeing a different part of the sky, and the light's coming from a different direction.
We can use the rotate tool of course, and fine tune that lighting and background. To get the view port to match the rendering, let's constrain the skydome to the camera. First of all, let's use the select tool and select the camera in the top view. And then shift select the skydome in any view. You can do it in the camera view. Shift select that skydome and then go into the animation menu set and choose constrain, point, options.
Just make sure that maintain offset is off, and constrain axis is set to all with a weight of one and click add. And now the skydome is constrained to the camera and we just need to increase the size of that skydome. We can go back to the skydome shape node, scroll down a bit into the section labeled view port, increase the sky radius to 70,000.
And now the sky is large enough and we can dolly back into top view. The skydome is now large enough to encompass all of the geometry in the scene. And that's how to set up an Arnold skydome for image based lighting.
- Arnold rendering concepts
- Lighting with Maya and Arnold lights
- Controlling exposure
- Filtering light with Gobo
- Light attenuation with Decay
- Image-based lighting with Skydome
- Exterior daylight with Physical Sky
- Arnold Standard Surface material attributes
- Mapping material attributes
- Rendering refractions
- Mesh subdivision and displacement at render time
- Shading effects such as ambient occlusion and vertex color
- Camera effects such as fisheye and depth of field
- Animation image sequence rendering