Learn how to control quad light properties.
- [Instructor] To learn more about the Quad Light Parameters let's set up this light as an ambient source of illumination outside the window. To best learn about those parameters, let's focus the light on the wall over here on the interior. I'm gonna do an active shade render. I've got that set up for the perspective view. Grab the light in the top view and use the Move tool to just bring it closer to the wall. As we do that, we can see the light intensity increasing in the Active Shade Interactive Production Render.
With that light still selected, let's choose the Modify panel. I'm going to drag the edge of the Command panel over to give myself two columns. Now I can see all of the parameters. Because Normalized Energy is off, then the total amount of light is effected by the size here. I'm going to click and drag on Quad X. Just click on that spinner and drag up and down and you can see clearly as the light becomes larger or smaller, the amount of light increases and decreases.
I'll set that Quad X value to four. Just type in a four and press enter. I'm using US Standard Units with a default units of feet so when I type in four, that's interpreted as four feet. Of course if you needed to, you could go into Customized Units Set Up and switch that over to metric. Let's look at these parameters here starting with Spread. If we click and drag on that spinner and bring it downward, we're essentially focusing the light. With a spread of zero, the light rays coming from the light plane are exactly orthogonal to that plane.
I can zoom in here with the mouse wheel in the top view. With a spread of zero, the rays of light are coming out exactly perpendicular to the light rectangle. Now it's a bit overexposed so we can fix that with the Exposure Value in the light. Select that and I'll type in a value of negative five. With the proper exposure now we can see that there's a gradient across the area here. It's brighter in the center and it fades out towards the edge.
That's controlled by the Soft Edge Parameter. If I bring that down to zero, now I've go a uniform field of light across the whole rectangle. If we want a round light instead of a square one, we can adjust the roundness. Bring that up to one and because the Quad X and Quad Y are equal, we get a perfect circle. That's how those Emit Light From parameters all work. Let's now set this up to represent that ambient illumination from outside the window.
I'll set the Roundness back down to zero. The Spread I want at its maximum of one and soft edges zero. Now I've got an even field of light coming out from that plane. I'll set the Exposure back up to what it was which is negative one. That's very bright, but we want to position that outside the window. First let's look at rotations. I'll go over to the Perspective View, right click and Alt and middle mouse to tumble around.
There's a line sticking out from the light. We can see it a little bit better if we deselect the light. That's the direction of the light, we want to turn that around. To make sure that it's turned around exactly the way I need it to, I'm going to use Gimble Mode for the Rotate Tool. Select Rotate and from the Reference Coordinate System pull down, choose Gimble. Select the light. In the Transform type in dialogue down here, we want values of X-90, Y-0, and Z of 180.
I'll type in 180, press Enter. Now the light's facing in the correct direction. It's also oriented properly so that later when I want to put a bitmap on here, it will be the right side up. We also want to move it outside. Let's dolly back in the top view with the mouse wheel. I'll right click to activate the top view and dolly back with the wheel. Position with the middle mouse button. Grab the Move tool and I already know where I want this to be outside.
I'll go ahead and type that in down here. I've got an X value of zero feet. A Y position of 30 feet. A Z position or elevation of 15 feet. I can dolly back in the front view with the mouse wheel. There's the light. It just needs to be a lot larger. Finally over here in Emit Light From, we can set the Quad X and Quad Y values, but before we do that, let's see the result interactively.
We'll go over and select the physical camera view. Just right click there. Go back into the Render Setup and we want to Active Shade Render the physical camera view. Unlock the View to Render and now in our Active Shade, we can see some light coming in there. Then lock it once again. Close the Render Setup and now we can adjust the size of the light and see the effect in the active shade window. I'll bring Quad X up, click and drag and as I do that, we can see a lot more illumination coming in.
Same with Quad Y, I can click and drag and increase that. I know what values I want so I'll just type those in. Quad X of 45 feet. Type that in, 45 and press Enter. Quad Y of 30 feet. We've got our light set up to represent the ambient illumination coming through the window. Don't worry about the grainy quality of the rendering here, of course we'll address that issue later. That's the basic parameters of an Arnold Quad Light.
- 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