Set Skydome lighting and camera backdrop options.
- [Instructor] In Arnold version 5, lights have visibility attributes that determine how much that light will contribute to the various render components such as diffuse and specular and volume. And for an Arnold skydome light, we can also control the visibility to the camera and through transmissive materials. Let's do a rendering. Go to the Arnold menu and choose render to open up the Arnold render view. Select the skydome in the viewport, and open up its attributes, Control + A.
At the top of the attribute editor for the AI skydome shape node are the skydome light attributes. Scroll down a little bit below that into the subsection for visibility. And now we can control each of the render components separately. For example, if I want hotter reflections in the river, I can increase the specular amount. I'm not limited by this slider. I can bring it down to 0 and I've got no specular reflections. Bring it up to 1, and I've got full specular reflections as determined by the physical simulation.
But I could just type in another value here, type in a 2 and press Enter. And now the specular reflections are actually brighter than the background. Bring that back to its default of 1. Likewise, we could control the amount of diffuse illumination. We could increase or decrease the diffuse slider, and that's just dimming down the light. Okay, bring that back up to 1. All of these attributes for different components are available in any light except for the camera and transmission attributes that we see here in the skydome.
And this allows the camera to see the skydome and it shows up in the background. We can dim down the background using the camera attribute. And now the brightness of the lighting hasn't changed, we've just dimmed down the background. Let's take a look at the alpha channel for this. Click on the display for alpha channel which looks like a circle with a checker inside it. And we get a white screen indicating that the alpha is completely solid and every pixel is opaque.
Turn that back off again. Go over to the visibility and reduce the camera slider all the way down to 0. And now the camera is not able to see the rays from that background. And this would be useful of course if we wanted to replace the background or maybe grade it differently in post. And once that camera attribute value is reduced to its minimum of 0, now the alpha channel does not recognize the background at all, so let's turn on the alpha channel. And boom, we can now easily replace that sky with some other image.
And it's anti-aliased against black so you won't have any trouble with color bleed if you're trying to use a completely different background. Okay, so we'll turn this back to RGB, and we can increase the camera slider back up to 1 to turn our rays back on again. This could also be useful if we wanted to look at a different part of the sky which might be brighter or dimmer. Go up to the AI skydome light, and we've got the rotation value.
Let's set the rotation in y to a value of 90 degrees. And now the sky looks over-exposed, but I kind of like the lighting that we have, so let's go back into the shape node and reduce the camera amount until we have a good exposure on that background. And that's how to work with the visibility attributes of a skydome to achieve different lighting and compositing effects.
- 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