10
Adjusting the Light Sources
The model can be illuminated by any combination of ambient light and up to seven individual light sources. This chapter explains how to adjust the positions, colours and intensities of the light sources, and whether the lights cast shadows.
10.1
Setting the Type of Illumination
Scroll the inner window up/down or resize the entire form to view the light the user wants to modify (Ambient, or Light 1 to 7) and the type of light the user wants to apply.
Note: The button switches the light on and off.
Ambient light represents a non-directional light source illuminating the whole model. This affects all surfaces equally, irrespective of their positions. The user can switch ambient light on and off, but the user cannot change its properties.
All the other lights can be set to the following types:
To control the model lighting, click the Lighting button on the toolbar (or select View>Lighting Control). This displays a Light Definition form which allows the user to set the characteristics of each light source.
Type Description
Infinite Directional wrt Viewer gives a parallel directional light whose position is fixed relative to the observer's eye point (like a light held by the observer). This is the default type for all lights. Both types of infinite light can cast shadows.
AVEVA Review User Guide
Adjusting the Light Sources
Each light source is defined in terms of its intensity, its colour, and its direction (for a parallel source at infinity) or its position (for a local point source).
10.1.1
Setting the Intensity and Colour
For all lights except Ambient, use the Type drop down list to specify the type of illumination for the current light.
Use the Intensity sliding scale and the Colour… button (to give the Windows Colour form) to set the overall intensity and the colour mix for the current light. The chosen colour will appear in the box above to the Colour… button.
10.1.2
Setting the Direction or Position
Click the Edit Position button on the Light Definition form. This displays a Light Position form.
Use the Positioning option list to select the light whose position the user wants to modify. (This need not be the same as that selected on the Light Definition form and is not, of course, applicable to Ambient light.) Having set the required options, Apply the form. If the user selects a light which has been defined as Infinite, only the Direction controls on the form will be available to the user; if the user selects a light which has been defined as Local, only the Position Light At controls will be available.
•
Setting the Direction of an Infinite Light Source
To set the direction of a parallel light, either type the required settings directly into the Bearing and Elevation text boxes, or use the corresponding graphical controls.
When setting the direction of an Infinite,
Directional wrt Model light, the
bearing and elevation settings define the absolute direction of that light.When setting the direction of an
Infinite
,Directional wrt Viewer
light, the bearing and elevation settings are defined relative to a viewer looking North. This principle also applies when manipulating Infinite, Directional wrt Viewer lights in the Keyplan Views. The default direction forInfinite
,Directional wrt Viewer
lights is for them to shine from behind the viewer's right shoulder.•
Setting the Position of a Local Light Source
To set the position of a local point source at the origin of an element in the display, enter the name of the element in the Position Light At text box. As an alternative, the user may position the currently selected light source (the active light) by using the Keyplan View window. To do so, set the Lighting control button, , in the Keyplan to On and then Local These lights represent omnidirectional light sources, usually positioned
within the model (like an unshielded light bulb fixed to part of the model's structure). These provide local illumination of surfaces which are orientated towards the position of the light source and have fixed positions with respect to the model.
Spot Light Gives a cone of light from a given position along a given direction. Type Description
Adjusting the Light Sources
drag the displayed light source to the required position. The position of the current light is shown in the Keyplan thus: .
•
Setting the Properties of a Spot Light
To set the direction and position of a spot light, either type the settings directly into the Bearing and Elevation text boxes, or use the adjacent controls.
The Spread option controls the light cone angle. The smaller the angle the narrower the cone of light.
The Exponent option controls how the light intensity falls off from the centre of the light cone to the outer surface of the cone. The minimum value is 0, which gives a gradual fall-off in intensity; the maximum value is 1, which gives a sharp fall-off in intensity.
10.2
Shadows
Exercise:
Tip: The easiest way to check the current settings is to switch each light on in turn, with all others off, and observe the effect on the displayed model as the user changes the light parameters.
Use the Light Definition form to set up white light for Ambient and at least one of each of the other types. For example, set Light 1 to be
Infinite
,Directional wrt
Viewer
; set Light 2 to beInfinite
,Directional wrt Model
; and set Light 3 to be Local.Switch on each light source in turn (with all others off) and, for each non-ambient light, adjust its position or direction (as appropriate) using the Light Position form so that it clearly illuminates the model. Observe the effect on the illumination of the Observer View as the user rotates the model.
Now switch on different combinations of light sources and again observe the effects on the Observer View model. If the user wants, try changing the colour of one or more lights.
Finally, use the Keyplan View, with the Lighting control button On, to move the local light(s). Select the Continuously Update Graphics button, , so that the user can see the effect of moving the light source as a user would do so.
AVEVA Review User Guide
Adjusting the Light Sources
To obtain the best possible performance and resolution of shadows, these guidelines should be followed:
• Use static shadows.
• Put the Observer View into Fullscreen mode (select Tools>Options>Full Screen), so that the shadow is created at the maximum possible resolution.