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Render

Light

Toolbar: Render > Lights (

Menu: View > Render > Light.

Keyboard: LIGHTING.

Alias: LIGHT.

The Lighting command activates the Lighting dialog box which allows you to specify how your drawing or scene is lit. You can control placement of the lights, light color, and light intensity. The Lighting dialog box, illustrated below, includes four buttons in the upper left corner of the window that allow you to select a preset lighting configuration. To the right of those buttons is a list of all of the lights currently defined in the drawing and buttons that allow you to add or delete from the list of lights. The change the characteristics of a particular light in the drawing, you first click on the name of the light in the light list. In the upper right corner of the window, the name of the selected light will be shown, as well as the color of the light and the light type.

Various other light parameters will be shown in the middle section of the window depending on the particular light type. Three types of lights are available to use in your drawing, Ambient light, Point lights, and Distant lights. An Ambient light illuminates the entire scene evenly (depending on the Ambient component of the Material finish). It does not cast shadows or change with viewing angle. A Point light represents light eminating from a single point in the drawing. Shadows will be cast by surfaces in the drawing and you will see highlights where the light reflects off of the surfaces. Point lights can also have a size or diameter to them so that they cast soft shadows. A Distant light represents a light from a large distance away from the surfaces in the drawing (e.g. the sun). All of the light rays are essentially parallel to each other so the shadows cast by the light have sharp edges.

The quickest way to specify a lighting configuration is to select one of the several preset light configurations provided including "Eye Light," "Side Light," "Sun Light," and "Back Light". All of these options add a small amount of ambient light and then a single point light. The Eye Light places the point light at the eye position for the scene. The Side Light option adds the point light at the upper right side of the scene. The Sun Light option adds a slightly yellowish light at a fixed point in the drawing coordinate system. The Back Light option adds the light behind and above the scene. Examples are shown below of the preset lighting on an example sphere.


Eye Light	Side Light

Sun Light	Back Light

In addition to these preset lighting configurations, you can add individual lights by clicking on the "Add" button to the right of the list. You can delete lights by first clicking on the light in the list and then clicking on the "Delete" button to the right of the list. When you click on a light in the list it becomes selected and the parameters for that light are shown in the lower part of the window. Once you have selected the light of interest you can modify its parameters using the controls in the lower part of the window.

Lighting settings are stored in the drawing.

Ambient Light

An ambient light illuminates the entire scene evenly and does not cast shadows or change with viewing angle. The parameters available for an ambient light are the light color and the light intensity. Ambient light can be used to fill in dark or shadowed areas of a drawing. It can also be used to make certain objects in a scene appear to glow. Note that too much ambient light will make the scene flat and lifeless since it flattens the shadows and highlights that provide depth cues.

Control	Description
Name	The name field is an arbitrary name you can specify for the light to identify it in the Lights list at the top.
Color	Clicking on the button in the color box will bring up a color selection dialog window that will allow you to specify the color for the light.
Intensity	The light intensity is specified using this slider that ranges from 0 to 200. 100 is full intensity and 0 is completely dark. This allows you to adjust the brightness of the scene. Values above 100 will produce a brighter scene, but may oversaturate some areas.

Point Light

A point light represents light eminating from a specific point in (or out of) the drawing scene. Several additional parameters are available for the point light including its position, and its diameter. The diameter controls the size of the light source and hence the sharpness of the shadows cast by the light. A true point light source would have a diameter of zero and casts sharp-edged shadows. A larger diameter makes the light source into an area light source that will cast softer-edged shadows. Note that soft-edged shadows require additional rendering time (please see the description of the Area Lights/Soft Shadows parameter on the Rendering Options dialog).
The position of the point light can be specified in several ways: in angles relative to the current view, in angles relative to the drawing World Coordinate System, or in drawing coordinates (X, Y & Z). If the "View" Coordinate System is selected as shown below, you will have the option to set the azimuth angle, elevation angle, and distance of the light relative to the current view. The azimuth angle is the angle in the horizontal plane relative to the scene center. Looking down from above, the camera position would be at zero degrees and the angle is measured clockwise. For example, 90 degrees would be to the camera's left, 180 degrees would be behind the scene, and 270 degrees would be to the camera's right. The elevation angle is the angle of the light above the viewing plane. An elevation angle of zero means that the light lies on the viewing plane, and an angle of 90 degrees means that it is straight above the scene center. The distance is the radial distance from the scene center to the light in drawing units. In this coordinate system, the light position will change relative to the drawing as you zoom, pan or rotate the view of the drawing.

If the "World" Coordinate System is selected, the same azimuth angle, elevation angle and distance parameters are available. In this case however, the angles are measured relative to the drawing's World Coordinate System. The Azimuth angle is measured in the X-Y plane with zero degrees being in the +Y direction and 90 degrees being in the +X direction. The Elevation angle is measure above the X-Y plane. The distance is the distance from the light to the origin of the drawing World Coordinate System (0, 0, 0).
If the "XYZ" Coordinate System is selected, the position of the light is specified using drawing coordinates (X, Y, Z) directly as shown below. These coordinates are relative to the drawing World Coordinate System.

Detailed descriptions of each of the entries is presented in the table below.

Control	Description
Name	The name field is an arbitrary name you can specify for the light to identify it in the Lights list at the top.
Coordinate System	Point lights can be positioned anywhere in the scene either relative to the viewer or relative to the scene itself. If View is selected, the light is positioned relative to the viewer and as the view is modified by rotating or panning the drawing, then the light position will move as well. If World coordinates are selected, then the light will be placed at a fixed position relative to the drawing itself and the azimuth, elevation, and distance parameters are relative to the drawing origin (0, 0, 0). If XYZ coordinates are selected, then again the light will be placed at a fixed position relative to the drawing and you can enter the light X, Y, and Z coordinates directly. Lights placed in either the World or XYZ coordinate systems will not change position as you zoom or pan the drawing.
Color	Clicking on the button in the color box will bring up a color selection dialog window that will allow you to specify the color for the light.
Intensity	The light intensity is specified using this slider that ranges from 0 to 200. 100 is full intensity and 0 is completely dark. This allows you to adjust the brightness of the scene. Values above 100 will produce a brighter scene, but may oversaturate some areas.
Diameter	The light diameter is specified using this slider that ranges from 0 to 1,000 drawing units. Larger diameters will produce softer edged shadows. A diameter of zero will produce a hard edged shadow.
Azimut	The azimuth slider allows you to position the light in the azimuthal direction. This is best envisioned as a compass heading. When working in World coordinates, the azimuth is measured by standing at the scene origin, with the compass N heading pointed in the +Y direction. The direction to the light is then read from the compass. For example, an azimuth setting of 90 deg would be in the easterly or +X direction. When working in View coordinates, the azimuth is measured by standing at the view center point with the compass N heading pointing at the eye position. An azimuth setting of 90 deg would then be to the viewer's left.
Distance	This is the distance in drawing units to the light from the view center point (in View coordinates) or from the drawing origin (when using World coordinates).
Elevation	This is the vertical angle between the horizon and the light. In World coordinates, this is measured from the X-Y plane through the origin to the light. In View coordinates, the horizon plane is the plane normal (perpendicular) to the view "up" direction. An elevation value of 0 is on the horizon and an elevation value of 90 degrees is straight up.
Light Coordinates	If the XYZ Coordinate system is selected, then lights can be placed using their X, Y, and Z coordinates directly. Text entry boxes will be displayed for each of the three coordinates.

Distant Light

A Distant light represents a light that is a large distance away from the surfaces in the drawing (e.g. the sun). All of the light rays are essentially parallel to each other so the shadows cast by the light have sharp edges. This option allows you to use a Sun Position Calculator that will calculate the position of the sun at any time of the day or year at any point on the earth's surface. With this type of light, the light's position is always calculated in the drawing's World Coordinate System. The Azimuth angle measures the compass bearing in the X-Y plane to the light and the Elevation angle measures the angle of the light relative to the X-Y plane horizon. By default, an azimuth angle of 0 degrees is in the +Y direction. However, this can be altered by adjusting the Site Orientation parameter on the Site Location tab of the Render Settings dialog.
As shown in the image below, on the middle right side of the dialog box, a Sun Position Calculator is available. This calculator enables you to calculate the position of the sun relative to any point on the earth's surface and any time. It contains entry blanks for the date and time. It also contains a button, "Edit Site Position", that will show the Site Location dialog and allow you to specify the latitude and longitude of the site represented by the drawing. Once you have set the site location, the date, and the time, you can press the button labeled "Calculate Azimuth and Elevation" and the software will calculate the sun position.

Control	Description
Name	The name field is an arbitrary name you can specify for the light to identify it in the Lights list at the top.
Color	Clicking on the button in the color box will bring up a color selection dialog window that will allow you to specify the color for the light.
Intensity	The light intensity is specified using this slider that ranges from 0 to 200. 100 is full intensity and 0 is completely dark. This allows you to adjust the brightness of the scene. Values above 100 will produce a brighter scene, but may oversaturate some areas.
Azimut	The azimuth slider allows you to position the light in the azimuthal direction. This is best envisioned as a compass heading. The azimuth is measured by standing at the drawing origin, with the compass N heading pointed in the +Y direction. The direction to the light is then read from the compass. For example, an azimuth setting of 90 deg would be in the easterly or +X direction.
Elevation	This is the vertical angle between the horizon and the light. This is measured from the X-Y plane through the origin to the light. An elevation value of 0 is on the horizon and an elevation value of 90 degrees is straight up.
Date	This is the date at which the sun position will be calculated. The sun position varies based on the day of year and also to a lesser extent the particular year.
Time	This is the local time of day in the timezone specified on the Site Location dialog. Note that daylight savings time is not automatically included so standard times should be used.
Calculate Azimuth and Elevation	This button will cause the sun's azimuth and elevation to be calculated at the specified time and date.
Edit Site Position	This button will show the Site Location dialog to allow you to adjust the site position (latitude and longitude), site time zone, and site orienation (relative to true north).