Learn how to illuminate a scene with an Arnold Skydome.
- [Instructor] In this chapter on Environmental Lighting, we'll look at Arnold's many powerful tools for image-based lighting, and daylight simulation. We'll start with the Arnold Skydome. And that is a mode of a standard Arnold light. I've got no lights in the scene currently. Let's see what it looks like with just default lighting. Click on ActiveShade on the main toolbar. And we have default lighting from behind the camera.
I've set up the exposure so that the default lighting is at about the right exposure level. Let's check in on that. In the Rendering menu, go to Exposure Control. And here I've got a physical camera exposure control, and I've disabled "Use Physical Camera Controls If Available", so that I can control the exposure from the Global Exposure value here. And it's currently at a value of eight, which looks good for the default lighting in this scene.
But I want this to look like natural daylight, at mid-afternoon. And appropriate exposure value for that would be about 13. I'll type in 13, and press Enter. And now, our shot is too dark in the ActiveShade window. But that's just because the default lighting isn't bright enough. Let's now add the Arnold Skydome. Close the Environment and Effects panel. I want the Arnold light to be oriented very specifically in the scene. And to accomplish that, I've enabled 3D Snaps, and I'm currently snapping to the grid points.
I'll go into the Create panel, to Lights. From the pull-down list, choose Arnold, click ArnoldLight, and in the top view port, click to create the light, and drag upward, release the mouse to create the light's target. And it's currently oriented the way I need it to be. Right click to exit the tool. And we can turn 3D Snaps off now. With that light still selected, go to the Modify panel, and rename it, and we'll call it Skydome.
Now, let's change the light type. And it's over here under Shape, and Emit Light from Type, we'll choose Skydome. And immediately we see illumination in our ActiveShade. It's too bright, so let's bring its exposure down. Under Intensity, set the Exposure to five. And we can see that we've got a white field, in the reflections in the dome. Let's turn on the Light Shape visibility in the Rendering.
Enable Light Shape visible. And now we see the Skydome is a flat white field in the background. We're ready now to add an image, for image-based lighting. And we'll go into the Color/Intensity section, enable Texture, and click the No Map button. In the Material/Map Browser dialog, double click Bitmap. And in the current projects scene assets images, select env_sky.
And that's a .exr document. Go ahead and click Open. In the OpenEXR Configuration dialog, just click OK. Now the image has been applied. If you don't see it, you might want to refresh the ActiveShade. It's there, but the mapping is all wrong, as we can see. Change the Format from Angular to Lat-Long. Alright, we've got our Skydome set up, and it's oriented correctly.
Let's check in on that. With the light still selected, choose the Rotate tool. And for the Reference Coordinate System, choose Gimbal. And you want to see these values down here. X of 90, Y and Z of 0. I'll re-select the Select Object tool. And we can play around a little bit with the parameters of the Skydome. The resolution value is defaulted to 1000. We can bring that down to a very low value of 10, just to illustrate.
And with a low resolution of 10, the reflections here are very blocky. If we set it to 100, and the reflections look better now, but they're still kind of fuzzy. I'll set it to a nice power of two number of 1024, and press Enter. We can control the balance of the various elements of the rendering. And that's done from the Skydome parameters. Scroll down into the section labeled Contribution.
And essentially, we can increase the exposure for just the diffused component. We've got the exposure value of five here, and let's bring that up by two stops, up to a value of seven. And now everything is four times as bright as it was. We can keep the diffused component at its current brightness but reduce the values for the Camera and Specular contributions. Set the Camera value to 0.25. And likewise, set the Specular value to 0.25, or one quarter.
So we've increased the exposure value by two stops, making the light four times as bright. We've kept the diffused contribution at its unity value of one. And we've set the Camera and Specular values to one quarter. The Skydome is a very powerful tool, but as we can see, we're not getting hard shadows. And for that, we'll want to use some other method, such as a distant light. We'll look at that in a subsequent movie. And that's how to use an Arnold Skydome, to provide image-based lighting.
- Arnold rendering concepts
- Arnold lights such as quad, spot, and distant
- Modifying Arnold object properties
- Filtering light with the gobo filter modifier
- Image-based lighting with Skydome
- Daylight simulation with Physical Sky
- Arnold Standard Surface material parameters
- Diffuse, opacity, and bump mapping
- Rendering refractions with Transmission
- Building an Arnold shading network
- Test rendering with utility map
- Mesh subdivision and displacement at render time
- Atmospheric perspective with scene environment fog
- Rendering a spherical environment with VR Camera