Construct a control for spotlight lens radius.
- [Instructor] For the key line in this triangle set up, we'll use a spotlight. It's going to represent direct sunlight coming through a window over here on this wall. There are other options for daylight. Usually you would use a Maya directional light. Create, Lights, Directional. If you create that, then it will be internally converted to an Arnold distant light type. In this case, we're using a spotlight because it's easier to arc direct.
Specifically with a spotlight, we can control the light coverage in the frame here without altering the set. The position of a directional light icon doesn't affect the lighting. The light comes from an infinite distance away from the model. If we wanted light from a directional light to reach the interior of the room, we'd need to cut a hole in the wall. Since the spotlight emits light from a specific location, we can place it inside the room and not have to edit the geometry.
Another advantage of the spotlight is that we can add a light filter called a gobo. This is a cut out or cookie effect that can accept any Maya texture map. The laser light from a directional light are parallel just like the sun. But the rays from a spotlight diverge from a spotlight location according to the cone angle. As we will see, the Arnold attributes for a spotlight allow us to achieve parallel rays or a collimated beam of light.
With the proper settings, we can optically and photometrically accurate daylight that we can arc direct very precisely. We'll start by just setting the exposure of the camera back to neutral. This is the state we're already in from the last movie. Go over to the camera view port and on the panel toolbar, click Camera attributes. In the attribute editor in the Arnold section, let's just set the exposure back to zero. I'm finished with the panel toolbar for now so I'll hide it with the keyboard shortcut which is Ctrl + Shift + M.
Let's create the spotlight. Go to the Create menu, Lights, Spot Light. It's created at the origin and it's very small. Let's rename it right away. Go over to the Channel box. At the top of the transfer node, rename the object to light key spot. Press Enter. We want to make it larger but it's bad practice to scale the lights so let's lock the scale channels. Select X, Y and Z scale by just dragging the mouse across there.
Right click and choose Lock Selected. To change the size of the light icon, we'll do that from its attributes under object display. Set locator scale to 50. Now we can see the cone here and we can zoom in on that. We can give focus to the perspective panel with the right mouse button and then press the F key to frame the selected object. As I mentioned a moment ago, we can set up the Arnold attributes to give us a collimated beam of light.
But we won't get good visual feedback in that process. In order to make it easier for us to see the size of the beam of light, we're going to create a simple rig for the spotlight and that will just simply be a nerve circle which will control the land's radius of the spotlight. Let's create a nerve circle. Create, Nerves Primitives, Circle. Rename it, go over to the Channel box.
Call it lens. Once again, we don't want to scale the object. We want to control its size from its attibutes. Click and drag across scale X, Y and Z. Right click. Once again, choose Lock Selected. In the Input nodes in the Channel box, click on makeNervesCircle. Scroll down a bit and here's the radius. Let's set it to 20. We can see if we tumble around with all the left mouse button. There's a nerve circle there.
Let's just play this in wireframe. Press the 4 key. It's a little bit easier to see now. Let's orient that circle with the light back up in the Channel box. Set rotate X to 90 degrees. Then apparent lens to the spotlight. The lens is already selected. Hold down Shift and click on the spotlight to select it as well and press the P key on the keyboard. Now if we select the Move tool and move the spotlight, the lens object follows.
- 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