Render the scene using Global Illumination

Setting a panel layout for rendering

The process of producing a rendered image usually involves rendering and evaluating successive test images to achieve the desired final image. This process involves adjusting many render quality, shading, and lighting settings in specific windows and panels. Opening and closing the various windows can become tedious.

Displaying the most frequently used windows and panels for rendering allows you to work more efficiently without having to open and close them repeatedly.

To set a panel layout for rendering

1. Close the Render View window.
2. From the perspective view’s panel menu, select Panels > Saved Layouts > Hypershade/Render/Persp.
   

   The panel layouts update to display the Hypershade window, Render View window, and Perspective view simultaneously. This allows you to easily work with these windows without having to open and close them repeatedly.

   If the image in the Render View window appears pixelated as a result of the new panel layout, do the following:

• In the Render View window menu, select View > Real Size. This resizes the rendered image to its actual size.
  Tip

  You can resize the panels in a preset layout by dragging the border between neighboring panels using your left mouse button.

Rendering the scene with Global Illumination

Now that the lights are set to emit photons and the Global Illumination preset is selected, you’re ready to render a test image using Global Illumination.

To render the scene using Global Illumination

1. In the Render View window, click the Redo Previous Render icon to render the image with the default Global Illumination settings.
   
2. When the image has completed rendering, click the Keep Image icon to save the image.
3. Visually compare this rendered image with the previously rendered images.
   

   In this rendering, the shadow areas of the scene appear less dark as a result of Global Illumination. The bowl also appears more transparent than in the previous rendering.

   The effect you want to achieve is to have the shadow regions receive indirect light; that is, you want to be able to view more detail in the shadow areas as a result of the Global Illumination. To do this, you must adjust the Global Illumination photon attributes. After you change an attribute, test render the scene to see the effect of this change in the rendered image. These repeated test renderings or iterations allow you to work systematically towards the goal of creating the desired final image.

In the next steps you use the Attribute Editor to increase the Photon Intensity to increase the overall Global Illumination for the scene.

Increasing the brightness of Global Illumination

Increasing the Photon Intensity setting increases the brightness of Global Illumination. The goal is to provide more visible detail and brightness in the shadow areas of the scene in the next test image.

To increase the Global Illumination lighting

1. In the Hypershade window, double-click on the icon for spotLightShape1 to display the attributes for the spotlight.
2. In the Attribute Editor, click the spotLightShape1 tab to display the lighting attributes for the spotlight.
3. In the Caustic and Global Illumination attributes adjust the settings to the following:
   • Photon Intensity: 120000

   Increasing the Photon Intensity increases the illumination in the areas affected by Global Illumination.

To render the scene

1. In the Render View window, click the Redo Previous Render icon to render the image.
2. When the image has completed rendering, click the Keep Image icon to save the image.
3. Compare this rendered image with the previously rendered images.
   

   The brightness of the illumination in this image has increased as a result of increasing the Photon Intensity. This is indicated by the increased brightness and details seen in the shadow areas of the scene. However, some circular spots have also appeared in the image along the dark wall behind the bowl. These spots are the result of low photon quality settings.

Adjusting the quality of Global Illumination

The quality of Global Illumination is primarily affected by three attributes:

• The accuracy of sampling (Accuracy)
• The radius size that determines the size of the region surrounding a particular sampling point (Radius).
• The number of photons (Global Illum Photons).

In the next steps, you return to the Render Settings window and the Attribute Editor to increase the quality attributes that affect the Global Illumination effect.

To increase the Global Illumination quality settings

1. In the Render Settings window, click on the Indirect Lighting tab and expand the Global Illumination section. Change the following Global Illumination attributes to:
   • Accuracy: 900
   • Radius: 2.5
     

   The Accuracy setting determines how many photons will be evaluated to determine the Global Illumination intensity at a given sampling point. Radius determines the size of the region surrounding the particular sampling point. The more photons that get sampled, the more even the Global Illumination will appear in the final image.

   Note

   As you increase the Global Illumination related quality and photon settings, the time to render the image also increases. Your goal should be to increase these settings just enough to achieve the desired image quality, without increasing them beyond what is required so that your rendering times are not adversely affected.

2. In the Render View window, click the Redo Previous Render icon to render the image.
3. When the image has completed rendering, click the Keep Image icon to save the image and then compare this rendered image with the previously rendered images.
   

   When the Accuracy and Radius values are increased, the resulting rendered image shows the circular spots have almost fully disappeared and the Global Illumination is much more uniform when compared to the previous rendering. Increasing the number of Global Illumination photons should aid in making the Global Illumination more uniform.

In the next steps, you increase the number of photons to provide a more uniform Global Illumination in the scene.

To increase the Global Illumination photons

1. In the Hypershade, double-click on the icon for spotLightShape1 to display the attributes for the spotlight.
2. In the Attribute Editor, click the spotLightShape1 tab to display the lighting attributes for the spotlight.
3. In the Caustic and Global Illumination attributes adjust the settings to the following:
   • Global Illum Photons: 80000

   When you increase the number of Global Illumination Photons you are increasing the resulting density of the photon map that gets produced at the beginning of the render process. The more photons, the smoother the resulting Global Illumination. Increasing the number of photons also increases the rendering time.

To render the image

1. In the Render View window, click the Redo Previous Render icon to render the image.
2. When the image has completed rendering, click the Keep Image icon to save the image and compare this rendered image with the previously rendered images.
   

   In this image, the circular spots that were seen in the previous renderings have disappeared. You can observe other Global Illumination effects compared to the original raytrace rendering:

   • Many of the objects have received some additional color from neighboring objects in the scene as a result of the Global Illumination, an effect known as color bleeding. When color bleeding occurs, objects take on some of the color from neighboring objects as a result of the reflected and transmitted light.

Now that you’ve tested and refined the Global Illumination for a small image you can render a final image for the scene at a larger image size and increase the rendering quality settings.

To increase the image size and antialiasing

1. In the Render Settings window, select the Common tab and open the Image Size settings.
2. Set the preset to 640 X 480 to render a larger sized image.
3. In the Render Settings window, select the Quality tab.
4. Open the Anti-Aliasing Quality attributes. Leave the Sampling Mode as the default (Adaptive Sampling) and set the following:
   
   • Number of Samples - Max sample level: 1

   Sampling is the process for determining the amount of anti-aliasing that occurs. The Sample Level attribute sets minimum and maximum limits for the amount of sampling that will occur for a given pixel area in the image. Modifying the anti-aliasing Sample Level settings will ensure that the surfaces in the rendered image appear smooth.

   A Max value of 1 should provide the correct amount of anti-aliasing sampling for this particular image at this image size.

To render a final image of the scene

1. In the Render View window, click the Redo Previous Render icon to render the image.
   

Saving your settings as a preset

You can save your settings in the Render Settings window as a preset so that you can retrieve your settings the next time you want to render using global illumination.

To save your settings as a preset

1. In the Render Settings window, select Presets > Save Settings as Preset...
   
2. Enter a name for your preset and click Save Preset.

   You can select Presets > Load Preset to retrieve your saved settings the next time you want to render using global illumination.