Lighting Types

Two types of lighting are available for MicroStation rendering, Source Lighting and Global Lighting.

Source lighting

MicroStation supports four source lighting types — Distant, Point, Spot, and Area, which come in the form of cells delivered in the cell library “lighting.cel.” Additionally, you can select from sample predefined light sources in the delivered DGN file “lightlist.dgn, “ or create your own predefined lights in that or another DGN file. Light source cells have a number of settings that you can adjust to get the correct lighting. For photo-realistic rendering, using Radiosity or Particle Tracing, you can use IES lighting files to set physically correct values for light Point, Spot, and Area light source cells (see Lighting considerations for photorealism)

During processing for rendering, the source lighting cells present in the active file always are considered. Any source lighting cells located in references, however, are ignored unless the Use Lights setting is turned on for the reference. You can turn on this setting in the Attachment Settings dialog box when you first attach the reference — click the Option button in the Attach Reference dialog box to open the Attachment Settings dialog box. For previously attached references, you can toggle the Use Lights setting on or off via the Attachments Settings dialog box, which is opened by selecting Settings > Attachment in the References dialog box.

Light sources present in references (that have Use Lights turned on) can be seen in the Lights list of the Define Light tool. Lights from references are displayed in collapsible lists under the number and name of each reference. You can view the settings of light source cells in references, but you cannot edit them from the active file.


Define Light tool with Light List displaying lights in both the active file and references.

You can use this feature to experiment with different lighting setups. For example, you can create multiple lighting files to which you can reference your models with Use Lights turned off, so that only the source lighting in the active file is used.

One of the settings for each light source, Lumens, is used for only for ray tracing (with Real World Lighting enabled), radiosity solving, and particle tracing. It is ignored by the other rendering modes. It lets you work with real-world lighting values for ray tracing, radiosity, and particle tracing solutions.

While not a light source in itself, there is a fifth source lighting option, Sky Opening. These are used in conjunction with Solar, Sky Light, and Distant light source lighting, when using Ray Tracing, Radiosity, or Particle Tracing, rendering modes. They restrict the calculations of the effects of Solar lighting, Sky Lighting, and Distant lights, to only that area represented by the Sky Opening. That is, only the illumination from Solar lighting or Distant Lights that shine through the sky openings is considered in the calculations. Similarly, all particles from these same light sources pass through the sky opening(s)

Light sources direct light as follows:

Distant Light — directional light, like the sun, producing parallel light rays, throughout the design. That is, the light source's orientation defines the direction of uniform light that illuminates all surfaces facing in its direction. This applies whether they are in front of or behind the light source, in the design. By default, Distant light sources have the same brightness as Solar lighting.

Distant Lights, if pointing upward, behave differently in the various rendering modes, as explained below (see Creating Distant Light Sources).
Point Light — light is radiated in all directions from the origin of the light source.
Spot Light — directional light having a conical beam, similar to a flashlight. Spot light sources having the same Lumens and Intensity settings as a Point light source may appear brighter in rendered images because the energy is restricted to the cone angle.
Area Light — useful for many diffuse lighting situations, such as simulating fluorescent lighting, where the light source is neither a Point light nor a Spot light. Area light sources are created from existing polygonal shapes in the design.
Sky Opening — used with Ray Tracing, Radiosity solving, and Particle Tracing, to generate more efficient solutions for indoor scenes lit with Solar Lighting, Sky Light, or Distant Light sources, through an opening in a wall or ceiling. Rather than consider the entire “sky” for calculating the lighting effect, only the lighting that is visible through the opening is considered.

By default, the delivered light sources all have their Intensity set to 1 and their Lumens value set to 1500.

IES lighting files can change the way that the Point, Spot, and Area lights direct their light.

A light source's settings are stored in enter data fields within the cell that represents it. Values that appear in fields in the Define Light tool settings window are read from the corresponding enter data fields in the light source cells (except for Lumens in the dialog box, which corresponds to the Brightness setting in the cell).