Lighting and Rendering Part II

S18 Loeb

Let's continue with interior lighting using Arnold.

You can use the SkyDome with an HDR (High Dynamic Range) image on it, or you might like to create the illusion that you are looking out onto something specific. For that you need to create a surface that is not affected by light and has an image attached to it. Here is how you do that:

Create a plane

Scale it up and rotate it so it is outside the window and totally fills the view from your cameraShot1 camera view.

If you render, you see that it is just a lambert back there. You don't want the material to respond to light in any way.

Open the Hypershade (icon next to the Render Settings) or Window>Rendering Editors>Hypershade

Open the Arnold Shader Section in the Create Node (where you find the aiStandardSurface material) and MMB Drag the aiUtility material into the Main Work Window and Click on the Graph Inputs and outputs arrows to see the nodes and connections for that material

In the small Attribute Editor for the material choose Flat for the Shape Mode

Now look at the render view

The plane is not interacting with the lights in the scene.

Then you can add an image to the plane by clicking on the checker to the right of the Color attribute for the material, choosing file, and then selecting the image file.

NOTE: The Image MUST be in the Source Images folder for that project for it to continue to work!

Be sure to move your image into the Source Images Folder before attaching it to the material or your links will be forever messed up.

Now your render view has the image out the window

NEXT: In the Attribute Editor for the polygon plane shape, in the Render Stats tab, be sure to uncheck

Casts Shadows and Receives Shadows

This allows you to still use the SkyDome for other indirect light later on.

Create the Sun

To get some strong lighting that looks like sunlight coming through the windows, a directional light is a good idea.

Create a Maya directional light and move it up into the scen so you can see the direction of the arrows.

A Directional light is infinitely long and infinitely wide. As a result, it doesn't matter where you put it, it only matters the direction the arrows point.

As you rotate the light, you will see the strong light and shadows. Play with the direction until you get something you like.

In the Attribute Editor for the light, In the Arnold Tab, turn on Color Temperature and change it to a kind of white light - around 5500K.

These lights have a hard edge around them - both the light areas and the shadows. To soften them, adjust the Angle Attribute under the Arnold Tab, changing it to a value around 3 in my scene works well.

At anytime, if you want to focus on a smaller region of the scene, to see how it is updating (and speed up your interactive rendering) you can choose a Render Region

Rename the directional light to sunlight

You can stop there with the natural light and start adding lights inside your scene, or you can make the scene look even better and more realistic by creating a Volume Light to create more atmosphere in your scene.

You will notice that your renders are taking longer. You could speed them up a bit by turning off a few settings in your Attribute Editor that aren't needed. For example, for the AreaLight(s) and the Sky Dome Light in your scene, you can turn off the Cast Volume Shadows option

You aren't using them but Arnold is calculating this value. Anytime you can speed up your render time while you work, you speed up your overall working time. You can up the quality for the final render.

Creating Some Volume Light Elements

Volume lights are used to create replicate the particles that float in the air. You can use aiVolumeLights but in this case, we will use a Maya Spot Light and Arnold's environment options.

Create a Maya SpotLight

Rename it volumeLight and Scale it Up and move it to the center of your room

One cool feature of a Spot Light is that you can give it an Aim, which means that you put the Aim locator on an object and the light will be directed towards it.

To get the Aim, with the volumeLight selected hit the t on your keyboard.

Now if you grab the Aim and move it out of the light and into the room, the spotlight follows the Aim Locator.

Position the locator towards the floor and move the volumeLight (spot light) outside the window falling in from a corner in a similar direction as where the sunlight is shining from. You want to replicate the sun direction, as much as possible, because the effect would be created by sunlight in a natural setting.

In the viewport Window there are some icons that allow you to adjust the lighting in that window. Hit the lightbulb icon to see the lights

Adjust the Volume light as best you can to replicate the sunlight pouring in but in the cone shape. It should be coming from the upper corner of the window in the same direction your sunlight is pouring in from.

Remember, you can move the Target around (hit t if you don't see the aim for the light) to help place the light.

You now need to adjust the properties of the light. In the Attribute Editor for the Volume (Spot) light, Turn ON Color Temperature in the Arnold Tab. And Adjust the Color Temp to a more orange color to replicate indoor lighting.

Depending on how things go later, we may need to adjust the color of the light through the light color attribute later on, but for now, try it this way.

Turn up the Exposure to a high number, like 20. Again, all these values will be different depending on the size of the room you modeled.

Keep looking at the renders to see how they seem.

You can change the direction of the light a bit to better match the sunlight, as needed, and to soften the shadow Edges, you can turn up the Light Radius Angle to around 1

In the Render Settings Window

Under the Environment Tab, Turn on Atmosphere (Create aiAtmosphereVolume) as shown above.

You won't see much, but you will see there is an Attribute Editor for the if you adjust (just a bit) the aiAtmosphereVolume, and if you turn up the density, even to .0001 or .0002

(again, depending on your room and settings, you may need a higher number to see this) but you should start seeing the atmosphere come in in the render view.

If you lose the aiAtmospereVolume tab in the Attribute Editor, you can find it again by clicking on the output arrow next to the aiAtmosphereVolume in the Render Settings Window

Adjust the Density up or down as needed to get a light atmsopheric effect. You also might want to play with the color in the aiAtmosphereVolume.

If it is black, there is no atmosphere, but adding some color give it a bit more visibility. I added a light orange color.

The Attenuation attribute is nice, it adds more falloff for the volume.

Then you can play with settings for the spotlight itself, increasing or decreasing the cone angle to fit your window, increasing the Intensity a bit. I increased the cone angle and added dropoff in the image below.

Play with your settings. Something between the first image and the second is probably better.

If you want the sort of "God Rays", I will show you how to do that in Part III of this tutorial.

When you get the volume light working as you want to, you can start to place lights inside the scene.

Check your Render Settings again. Turn up Samples for Diffuse and Volume to around 2 or 3. Adjust everything (Area Lights, Directional Lights, Volume/Spot Lights) to get the balance of seeing the background image with the amount of sunlight and the amount of volume until you get a look you like. This is an art and takes time and practice. Save along the way when you like something so you can find it again in your Incremental Saves, or rename the saves wiht a name that helps you find the version you liked.

Color correct to change the sense of time of day, too.

Incidental Lights

You can make lights inside the room in a number of ways, and remember, in the real world, depending on how bright your daylight is, you either need the lights on, or you don't. Everything is relative to each other! I'll show you one way to do it. by creating a lightbulb inside the lamp by the table and turning that into an Arnold Mesh Light.

Since, in my lamp, the lightbulb doesn't show, I just created a sphere. If the bulb shows, you may need to shape it more. For the recessed lights I put in my scene, I can just use the fixtures themselves as the mesh lights. So it depends on what you have and how you want it to look.

For the lamp, I want a bright light inside with the shade creating a surface that limits the throw of the light itself and makes the light spill down onto the table.

Select your object and the choose the aiMeshLight

You don't see much affect from the mesh light yet.

Increase the Exposure on the meshLight (renamed to LampLight) to a big number like 20, and then reduce that until it starts to look good.


To see the bulb itself, make it Visible in the MeshLight Attribute Editor:

Using a Render Region makes sense here because the render times are slow.

As with any lighting, give the light a color. You can do that with the Color Attribute, assigning a slight orange tint or a green if it was fluorescent, or whatever color you want.

Up the number of light samples to increase the quality

You will quickly notice two things:

  • The renders take longer
  • The image is less grainy

Samples increase quality but slow things down. It is an optimization problem and worth playing around with as you start doing your final render. Remember, there is a huge difference between 3 samples and 4. Every increment increases both time and quality.

When you go back to your ShotCamera view, you will need to adjust the mesh light exposure to have it show. You may also notice the light from the bulb is being impacted by the volume effects you created depending on the exposure.

You can keep going with adding lights, using point, spot, or mesh lights as back ligths, or letting bounced light do the same thing. You won't want volume passes for most lights and can turn those off as you did for the Area Light.


When you are ready to render you final image, you need to turn up the samples. In the Light Manager, your samples for each light should be at least 3 or 4, 4 for lights with volume, most likely.

You probably want to turn up the Render Settings Sample Rate, too.

Of course many of these settings will depend on whether you have transmissive materials in your scene and whether you are using sub surface scattering. If you are, you may want to turn those settings up a bit. The higher the number the longer the render.

Turn off Interactive Render and Refresh the Render

You will notice the renders take quite a bit more time.

You probably want to turn down your settting some as you start to set up your materials and textures. Keeping rendering quick will help you see changes and speed your production time. We can set things higer for the final render later.