3ds Max 2012 Bible - Kelly L. Murdock [249]
Light shapes
In addition to the distribution type, you can also select the light shape, which has an impact on how shadows are cast in the scene. Selecting a different-shaped light causes the light to be spread over a wider area, so in most cases the Point light results in the brightest intensity with sharper shadows, and lights covering a larger area are less intense and have softer shadows. The available photometric light shapes include the following:
• Point: This shape emits light from a single point like a light bulb.
• Line: This shape emits light from a straight line like a fluorescent tube.
• Rectangle: This shape emits light from an area like a bank of fluorescent lights.
• Disc: This shape emits light from a circular area like the light out of the top of a shaded lamp.
• Sphere: This shape emits light from a spherical shape like a Chinese lantern.
• Cylinder: This shape emits light from a cylindrical shape like some kinds of track lighting.
For each shape you can set the shape's dimensions in the Shape/Area Shadows rollout. The rollout also lets you switch between the different shapes. If you need to see the actual light shape, then you can enable the Light Shape Visible in Rendering option in the Shape/Area Shadows rollout.
Using the Sunlight and Daylight Systems
The Sunlight and Daylight systems, accessed through the Systems category of the Create panel, create a light that simulates the sun for a specific geographic location, date, time, and compass direction. You can also create them using the Create⇒Lights⇒Daylight System menu command.
Note
The Daylight system can be created using the Create⇒Lights menu or the Create⇒Systems menu, but the Sunlight system cannot be created using a menu. •
To create either of these systems, open the Create panel and click the Systems category button. Then click the Sunlight (or Daylight) button, and drag the mouse in a viewport. A Compass helper object appears. Click again to create a Direct light (or Skylight) representing the sun. Figure 20.11 shows the Compass helper created as part of the Sunlight system. The main difference between these two systems is that the Sunlight system uses a Directional light and the Daylight system uses the IES Sun and Sky lights.
Note
When you first create a Daylight system, a warning dialog box appears giving you the option to enable the Logarithmic Exposure Control for external light. Clicking the Yes button makes this change for you automatically. •
Note
The Compass helper object's orientation aligns with the ViewCube's directions. •
Tip
The best results for the Daylight system are realized when you use the mr Sun and mr Sky options. Using the Daylight system with these options also enables the mr Physical Sky environment settings. More on this system is covered in Chapter 47, “Rendering with mental ray and iray.” •
FIGURE 20.11
The Compass helper provides an orientation for positioning the sun in a Sunlight system.
Using the Compass helper
The Compass helper is useful when working with a Sunlight system. It can be used to define the map directions of North, East, South, and West. The Sunlight system uses these directions to orient the system light. This helper is not renderable and is created automatically when you define a sunlight object. The Compass helper object is found in the Create⇒Helpers menu.
After you create a Sunlight system, you can alter the point that the sun is pointing at by transforming the Compass helper. Doing so causes the direct light object to move appropriately. The light's position in the sky is controlled by the Time, Date, and Location parameters, but if you want to move the light independent of these parameters, you can select the Manual option and move the light using the transform tools.
Note
You can change the settings for the light that is the sun by selecting the light from the Select by Name dialog