Global Lighting

You use the Global Lighting dialog box to define the settings for Ambient, Flashbulb and Solar lighting. Additionally, you can turn on Add Sky Light to all Solar and Distant Lights and Approximate Ground Reflection for Sky Light to simulate lighting from the sky and reflected light from the ground, respectively.

To open the Global Lighting dialog box

Select the Global Lighting tool in the Rendering Tools tool box.
or
From the Settings menu's Rendering submenu, choose Global Lighting.
or
In the Define Light tool's dialog box, click the Global button.

The following table covers the controls and settings of the Global Lighting dialog box.

Tool setting:	Effect:
Ambient	If on, enables controls for setting the intensity and color of ambient lighting. Intensity — can vary from no light (0) to full light (1). Color — Opens the Modify Color dialog box, to set the Ambient lighting color.
Flashbulb	If on, enables controls for setting the intensity and color of the view flashbulb. Intensity — can vary from no light (0) to full light (1). Color — Opens the Modify Color dialog box, to set the Flashbulb lighting color.
Solar	If on, enables controls for setting the intensity and color of the solar lighting. Clicking the Show Solar Settings button, at the left, expands the dialog box to display all Solar lighting settings. See Solar lighting settings.
Add Sky Light to all Solar and Distant Lights	If on, enables the color button for the lighting. Clicking the Show Sky Settings button, at the left, expands the dialog box to display all relevant settings. See Add Sky Light to all Solar and Distant Lights settings.


Global Lighting dialog box, fully expanded.

Ambient

Ambient light is all-pervasive. That is, it illuminates all surfaces equally. It is controlled in the Global Lighting dialog box.

The intensity of ambient light can vary from None (0) to Full (1.0), and its color can be adjusted.

Because ambient light illuminates all surfaces equally, increasing its intensity reduces the depth, or contrast, of the shaded view.

Ambient light is useful, however, in simulating background office lighting or illuminating surfaces that would not otherwise receive light. No shadows are cast by ambient light.

For Radiosity solving and Particle Tracing, it is normal to turn off Ambient lighting. If you forget to do this, an alert box gives you the option to do so prior to commencing the rendering process.


Ambient lighting with Intensity set to 0 (left), 0.20 (center), and 0.40 (right).

Flashbulb

Flashbulb light provides a point light source from the eye-point of the view. It is controlled in the Global Lighting dialog box.

The intensity of flashbulb light can vary from None (0) to Full (1.0), and its color can be adjusted. Flashbulb lighting does not cast shadows.

For Radiosity solving and Particle Tracing, it is normal to turn off Flashbulb. If you forget to do this, an alert box gives you the option to do so prior to commencing the rendering process.


The effect of flashbulb light, showing Flashbulb off (left) and on (right).

Because it always originates from the camera, or eye-point, of the view, flashbulb lighting is convenient to use for a “first try” rendering, before any other light sources are introduced.

Solar

Solar light simulates light from the sun. It is controlled in the Global Lighting dialog box.

You can specify whether or not shadows are cast by the solar light. To display shadows requires that Shadows also be on in the Rendering View Attributes dialog box and for ray tracing in the Ray Tracing dialog box.

As well as being able to specify a location and time for the Solar lighting, you can define the direction of North in your design. This can be input manually as a value of degrees from X axis, or you can define North graphically.

Where you specify that the “Sun” is below the horizon, then the Color button for Solar changes to black and its title changes from “Color” to “No Sun” and Solar lighting will not illuminate the scene.

You can create a sequence of images that shows the locations of shadows cast by the sun over a period of time using the Solar Study utility. For instructions see Conducting Solar Studies.

Add Sky Light to all Solar and Distant Lights

With this setting turned on, you can add atmospheric lighting from the sky. A color button lets you define the color of the sky light.

When this setting is turned on with Solar lighting, the intensity of the light is modified by the angle of the Sun (providing a more realistic solar study). As cloudiness increases, the direct sunlight decreases but the amount of light from the sky increases. Similarly, the light from any Distant Light sources is modified.

You can set the amount of Cloudiness and the Air Quality (Turbidity) to create the desired conditions. On a clear day, for example, the sky is not uniformly lit. More sky light comes from the direction of the Sun, thus producing darker, sharper shadows. Alternatively, on a cloudy day, the sky is uniformly lit with softer, less pronounced shadows.

With Air Quality (Turbidity) set to Perfectly Clean, there is a small amount of coloring from the sky lighting. When Air Quality (Turbidity) is set to Industrial, the coloring effect of the sky lighting is more pronounced.

Sky light is a directional light coming from each direction of an imaginary sky hemisphere. The precision of the hemisphere is determined by the sky samples setting.

When using Solar lighting or Distant Lights to illuminate an interior scene, through windows for example, it is more efficient to create sky openings to “focus” the calculations to only that light coming through the windows.


Ray traced image without added Sky Light (left) and with added Sky Light (right). With added Sky Light, shadows are less stark and objects that were hidden in the shadows of the larger object now become slightly visible.

Approximate Ground Reflection for Sky Light

This setting is used to create an approximation of all Sun and sky light reflected by the ground. A color button lets you define the color for the ground reflection. Typically, this setting would be used only where a model has been created without any ground geometry. If you have ground geometry in the design, it would cast shadows and/or reflect its own light.

Solar lighting settings

When Solar is turned on, in the Global Lighting dialog box, the Intensity and Color settings are enabled. Clicking the Show Solar Settings button, to the left of the Solar toggle, expands the Solar section of the dialog box to reveal more solar lighting settings.

Solar setting:	Effect:
Intensity	Sets the intensity of the Solar light — can vary from no light (0) to full light (1).
Color	Opens the Modify Color dialog box, to set the Solar lighting color.
Solar Shadows	If on, solar shadows are created in Phong rendering, ray traced and particle traced images, as well as radiosity solutions. This requires also that Shadows be on in the Rendering View Attributes dialog box and for ray tracing, in the Ray Tracing dialog box.
Solar Shadow Resolution	Sets the resolution of the shadow map generated for the solar light with Phong rendering. The lower the value, the less resolute the solar shadows will be, and processing time will be reduced. Has no effect on ray traced images.
True North Direction (degrees from X axis)	Specifies the direction of North as degrees from the X axis.
Define By Points	Lets you define the direction of North, graphically, with two points.
Solar Direction Vector X, Y, Z	Specifies the direction vector from the solar light. Dimmed if Lock is off.
Azimuth Angle	Sets the azimuth direction of the solar light (from 0-360°). Dimmed if Lock is off.
Altitude Angle	Sets the angle of the “sun” above the horizon (from 0-90°). Dimmed if Lock is off.
Lock	Sets how the position of the solar light is determined: On — the position of the solar light is determined by Vector values. Off — the position is determined by Location and Time settings.
Location	Contains controls to set the model's location for calculating Solar light. These controls are dimmed if Lock is on. Longitude — sets the longitude at the model's location. Latitude — sets the latitude at the model's location. GMT Offset — Sets the time difference from Greenwich Mean Time (GMT) at the model's location. Cities — Opens the Location By City dialog box, which is used to set the location by selecting a city from the list. Map — Opens the Location By Map dialog box, which is used to set the location by pointing at the location on a map of the world. Zones — Opens the GMT Offset By Time Zone dialog box, which is used to set the GMT Offset by selecting a time zone.
Time	Sets the time of day and the year for the rendering. Time — sets the hours and minutes, with option menus for AM or PM and Standard or Daylight time. Date — sets the date for the rendering. Year — sets the year for the rendering.

To set solar lighting using the Cities button

In the Global Lighting dialog box, turn on Solar.

Click the Show Solar Settings button.
The dialog box expands to display further solar settings.

In the Location section of the dialog box, click Cities.
The Location By City dialog box opens.

Select a city from the list.

Click OK to accept.
The dialog box closes and the Latitude, Longitude, GMT Offset values are updated to match those of the selected city.
If you click Cancel, the dialog closes without changing the values for Latitude, Longitude, GMT Offset.


Location By City dialog box

To set solar lighting using the Map button

In the Global Lighting dialog box, turn on Solar.

Click the Show Solar Settings button.
The dialog box expands to display further solar settings.

In the Location section of the dialog box, click Map.
The Location By Map dialog box opens.

On the map of the world, click the required location.
Latitude and Longitude values below the map of the world update to the selected location.

In the GMT Offset field, key in the correct value.
If you do not enter a value in the GMT Offset field of the Location By Map dialog box, an Information box will alert you that you must enter this value manually when you click OK to accept.


Location By Map dialog box

To set the GMT Offset using the Zones button

In the Global Lighting dialog box, turn on Solar.

Click the Show Solar Settings button.
The dialog box expands to display further solar settings.

In the Location section of the dialog box, click Zones.
The GMT Offset By Time Zone dialog box opens.

Select a time zone from the list.

Click OK to accept.
The dialog box closes and the GMT Offset value updates to match that of the selected zone.
If you click Cancel, the dialog closes without changing the value for GMT Offset.


GMT Offset By Time Zone dialog box

Add Sky Light to all Solar and Distant Lights settings

When Add Sky Light to all Solar and Distant Lights is turned on, in the Global Lighting dialog box, the Color setting button is enabled. Clicking the Show Sky Settings button, to the left of the Add Sky Light to all Solar and Distant Lights toggle, expands the dialog box to reveal additional settings.

Sky Light setting:	Effect:
Color	Sets the color of the Sky Light.
Sky Shadows	If on, shadows are generated from the Sky Light.
Jitter sky samples	(When Sky Shadows are on only) If on, sky samples are taken in a non-uniform manner, to create a softer image.
Cloudiness	Sets the cloudiness of the sky. Can vary from Clear (0) to Cloudy (1).
Air Quality (Turbidity)	Sets the purity of the air. Can vary from Perfectly Clean (1) to heavily polluted (9). An option menu provides commonly used settings.
Sky samples	Sets the precision of the sky hemisphere. Higher values more accurately simulate sky lighting, but processing time increases. An option menu provides default values for the various rendering modes.
Approximate Ground Reflection for Sky Light	If on, enables its Color button with which you can specify the color for the ground reflection of incoming sky and sunlight.
Ground Reflection	(When Approximate Ground Reflection for Sky Light is on only) Sets the amount of reflection from the ground, from None (0) to Full (1).