Interior rendering tutorial

Interior renderings are the most difficult renderings to complete. They rely on many different light sources and require the calculation of indirect light. All of this can lead to longer rendering times then the standard exterior or product rendering. There are also a few things we need to know before starting.

• Lighting pre-sets – Unlike almost every other render situation, the Studio lighting preset will not work well for interiors. There are two lighting presets for Interior lighting.
• Interior Daylight - This is a daylight mode with sun and sky. Artificial lights are turned off. Indirect light is on.
• Artificial lighting – In this case it is nighttime and the artificial lights are the only lights that are on. Indirect lighting is on.

Daylight rendering

The main aspect of rendering daylight situations are the windows of an interior. While it might seem self evident to some, windows are very important to interior renderings. In NXT we treat glass windows specially. So, windows should exist as a single surface and be assigned a transparent material to work properly. You will find the more windows a space has; the easier it is to light.

To setup nXt for an interior rendering:

1. Open the Interior Starter model.
   This model has materials, but some of the materials have not been assigned to objects or layers.
2. Set the lighting preset to Interior Daylight.
3. Render the model.
4. Stop raytrace after 5 or 6 passes.
   The result is less than spectacular. Since the windows have not yet been assigned as glass, they are a default opaque material. The result is very flat because no light is getting into the scene from the outside.
   
   Scene before window layer is assigned to glass material.
   
5. Assign Glass material to the Window layer.
   All the objects on this layer will render as glass.
6. Render the model.
   You can see the daylight start to come into the space. Make a note about how the first few passes there are many lighting changes that are going on. As the number of passes increase the lights will change less and less, and the lighting effects will get smoother.
   Interiors can require several passes. At 7 passes the image is usable.
   
   Scene after window layer is assigned to glass material—image after 7 passes.
   
   At around 25 passes the rendering looks much better.
   
   Scene after window layer is assigned to glass material—image after 25 passes.
   
   At 35 passes it is still improving. You can choose when you want to stop it and save the results.
   
   Scene after window layer is assigned to glass material—image after 35 passes.
   
   1. After you Stop Raytrace, you can adjust the Brightness slider in the Adjust Image section of the render window.
      This will adjust the overall brightness of the image. Many variations are possible using brightness.
      
      
      Scene after brightness was adjusted to 0.30.
      
   2. After you’re satisfied with your adjustments, Save the image.

   Artificial lighting

   
   Artificial lighting is the second set of lights you have to light an interior. There are two styles of artificial lights in NXT.
   • Tagged lighting
   • Idealized lighting
   
   Tagged lighting is the recommended lighting style to use for most architectural applications. Because any surface or mesh can be tagged as a light, your light can be any shape or size.

   Idealized lights are the standard Point, Spot, Rectangular and Linear light sources.

   In this part of the tutorial we will use tagged lighting.

   To tag an object as a light:

   1. In the nXt Control Panel, click the Lighting tab.
   2. In the Presets dropdown, select Artificial lighting.
   3. Select the two cylindrical objects over the fireplace, click on the leftmost button to tag the objects as lights.
      
      Tagged lights and channels diagram.
      
      In addition to tagging the objects as lights, we can also set the properties of the tagged lights.
      
   4. In the Flamingo nXt Control Panel, on the Lighting tab, select both light definitions and right-click, click on Properties to bring up the Edit Lights dialog.
   5. Name the lights Fireplace, set the LightDistribution to Diffuse, Watts=100, and Channel=2.
      
      Edit Lights dialog.
      
   6. Repeat steps 3 through 5 for each set of ceiling lights:
      Living 1--Channel=3, Living 2--Channel=4, Dining--Channel=5,
      Counter--Channel=6, Kitchen--Channel=7
      
   7. Render the model.
      You will notice that there is no daylight coming through the windows. When you change to Artificial lighting, the Sun and Sky are turned off. The artificial lights are creating all the light. Like the other renderings, the number of passes will continue to improve the lighting effects.
      
      Interior rendering with all artificial lights turned on.
      
   8. After you Stop Raytrace, Save the image.
      To preserve the lighting channels in an image, we must use the NXT image format.
   9. Before you close the Render window, on the Save dropdown, Export to native Flamingo nXt file.
      This file can be opened with the Flamingo nXt Image Editor for editing.

Lighting Channels

Flamingo nXt has the ability to put lights into channels. These channels and the lights in the channels can be edited after the rendering is finished without the need to render the model again. This can save time and allow you to make subtle changes without a lot of effort.

To use Channels for editing a rendered image:

Since we’ve already assigned the tagged lights to channels, we don’t need to do that again. But we will need to assign the Sun and the Sky to channels.

1. On the Lighting tab, click Advanced.
2. Turn the Sun On and change the Sky to Auto.
3. Click the Sun and Sky tab.
4. Change the Sky channel to 1.
5. Render the image.
   
   Interior rendering with all light sources turned on.
   
6. After you Stop Raytrace, Save the image.
7. Before you close the Render window, Export to native Flamingo nXt file.

To edit the channels:

1. From the Flamingo nXt menu, click Open the NXT image editor.
2. Open the last nXt image you saved.
3. On the Channels tab, you can adjust the strength of each channel.
   
   Interior rendering with living room and fireplace light channels turned on.
   
4. Try adjusting different channels and changing the scene.
   
   Interior rendering with Fireplace, Dining, Counter channels turned on.
   
   Interior rendering with the Kitchen and Counter channels turned on.