Now that you have grasped the main concepts behind the Arnold renderer, let’s see how you can put them to good use to light an architectural interior. Open the file named Room_start.max. A download link is available in the description section of this movie. The scene shows a rectangular living space, with a few pieces of furniture making up that interior. The renderer has already been set to Arnold. All objects are currently assigned the same gray material, except for the glass pane that has a thin-walled transparent material. We’ll deal with better materials in a moment but first, let’s look at using lights to illuminate the scene. A render at this point would be very dark. That’s understandable given the lack of lights in the scene. Typically in this kind of scenario, you need to simulate sunlight and daylight coming from outside. Usually, you would use a daylight system or the more current Sun Positioner. You can indeed use the Sun Positioner as it is certainly compatible with Arnold. However, using the Sun Positioner also places a Physical Sun & Sky map as an environment background. This can be seen in the environment dialog that you can open by pressing the 8 key. In Arnold, you can get better sampling by using an HDR background in conjunction with a Skydome light. So, let’s look at lighting the scene using only Arnold lights. Clear the Environment map and delete the Sun Positioner altogether. This basically takes you back to square one. Using Arnold Lights to simulate the sun, you would want to start with a Distant light for direct illumination. You can click and drag to place it in the top view and then use the Move tool to adjust the position of both light and target. Render again to see the results. You can see the effect of direct sunlight in the scene and you can see the effect of indirect lighting as well. However, indirect lighting can be helped further by using a Skydome light. You will see its benefits in a second. Add another Arnold light in the top view. This one would be based on a Skydome type and doesn’t need to be targeted. This is a global light so you can click anywhere in the top view to place it. Render the scene again and see how the skydome added illumination to the scene. We’ll make further adjustments in a second. There is a fair bit of noise in the render. One of the reasons is we haven’t adjusted the render settings yet. The rendering currently takes a mere 18 seconds on the PC I am using to record this tutorial. We can help with the final gather solution by adding a portal outside the glass window. When doing so, you would need to tell the Skydome light how to treat portals. By default, Portal Mode is off so adding portals would have no effect on the rendering. You can set the Skydome Portal Mode so that portals affect exteriors and interiors, or interiors only. Since this is what we have here, we’ll use that option. Deselect the skydome when done. Deselct the Skydome when done. To place a portal that covers the large window, use a Quad light. Place one in the left view so that it is oriented properly. When you set this light as a portal in the Modify panel, all parameters except for the size of the light become unavailable. Adjust the size, and move the portal outside the room in the top view. Try another render. You should see an improvement and less noise in the rendering without a significant increase in render time if any. Let’s improve the render a bit more. Select the distant light and increase its samples to 5. Do the same with the skydome light. This improves the rendering with only a slight increase to rendering time. We can yet increase rendering quality by changing Arnold Settings in the render dialog but we’ll do that a little later once we’re done testing. The next thing to consider is to replace the white global light with proper environment lighting. Good environment lighting usually comes from HDR panoramic images. If you don’t have any, you’ll find a good resource in HDRLabs. You can visit their archives atto find and download an HDR image that you like. In this case, we’ll be using the Barcelona Rooftops image. Go ahead and download it to your system. Unzip the archive, and drag the 3k .hdr image to your working folder. Once you have done that, drag the image into the Material Editor. There it’s important to set the image in Environment>Spherical mode so that it wraps up around your scene properly. I usually like to set the U Tiling value to -1 as we are effectively mapping the inside of a virtual sphere, not the outside. You can also adjust the U Offset to rotate the panorama left and right. Set it to -0.25 for this exercise. Make sure the skydome is selected and set it to work in Texture mode instead of color mode. Drag the HDR image output into the texture slot of the skydome. Under the Shape section, change the Format to LatLong (Latitude/Longitude) which is what this hdr image is. Also, it’s good practice to set the light resolution to that of the image resolution, in this case 3000, or 3k Render again. The indirect lighting should be significantly different and more natural now. Still, it’s kind of funny to see environment reflections without an actual background, so let’s see how we can set that up. Look at the Render Settings dialog, under the Arnold Renderer tab. A little lower in the dialog, you will see a section where you can specify a Backplate as a Background. Switch the backplate source to use a Custom Map, and then use the same HDR image in that channel. Here you need to be a bit careful as dragging the map as a backplate tends to reset it to a Screen environment. Make sure you set it back to Spherical Environment before you test-render once again. The Barcelona rooftops should be visible now. Here’s a bit of a trick you can do with HDR backplates: you can set a manual exposure to make them brighter or darker. This can be very useful for simulating a different time-of-day for example. Right-click in the Material Editor and choose Maps>Arnold>Color>Color Correct. A new color correction node is added. Connect the HDR image to the Color Correct input channel, and then double-click to see its properties. The only entry you need here is Exposure. The higher the value the brighter the background. Negative values work well for a night scene. For this to work, you need to assign the Color Correct node to both the skydome and the backplate. Again, double-check that the hdr image is in fact used as a spherical environment map. Try Exposure values of -1 … or +1 … to see the effect on the scene. A value of +1 seems to work well in this context, we’ll keep it. If you want even more control over skydome lighting and backplate, you can use separate color correctors. An exposure value of +1 seems to work well for the skydome light but the backplate is a bit dark, especially when seen through the glass. You can duplicate the color corrector and use the duplicate with a higher exposure (2 should work well in this case) as a backplate. Again, ensure the image is set to Spherical environment before rendering. The inside looks the same as before but the backplate is now even brighter. The sunlight (Distant Light) is a bit too bright and too white considering the background. Select it and bring its Exposure value down a notch to about 7. You can also change the color to a light yellow or sample it from the VFB. Next we’ll add some more life to the room in the form of better and more colorful materials. You can certainly take some time and experiment on your own or you can use some materials and props that are made available to you. If so, start by selecting all the furniture and delete them. You’ll be merging a textured version of each part. To select the furniture, make sure Scene Explorer is set to Layer mode and select all objects under the Furniture layer. Before you import the furniture back let’s work on the room for a second. In the Material Editor, you’ll notice a view named Room. In it, there are various Physical Materials defined to cater for the parts that make the room. Apply the appropriate materials for the floor, ceiling, walls, and the two metal columns. As mentioned, you can experiment by building your own materials if you prefer. Ultimately, you want to merge back the furniture and other props. You can do so by merging all objects from a scene named Props.max that you downloaded for this tutorial. Try a render again, it should look much better as the room is more populated. Of course, the rendering is still low quality and only taking under a minute to process. To improve it, go to the Render Settings dialog to adjust the Arnold rendering properties. Set the Diffuse sampling to 6 with a ray depth of 2 to increase Diffuse bounces. You can leave the rest as is or even cancel SSS and Volume Indirect calculations as you’re using neither in this case. The rendering will take a little longer, two or three minutes in my case but should look much better. From this point on, simply adjust the Camera AA value to crank up the quality even higher. With every degree that the Camera AA value increases, the sampling and rays numbers for Diffuse, reflections and transparency get multiplied. This will significantly increase render quality but also render time. In the next and final movie in this series, you learn how to set up your projects to render stereoscopic 360-degree scenes for VR purposes.