Using Volume Lights

When light shines through fog, smoke, or dust, the beam of the light becomes visible. The effect is known as a Volume Light. To add a Volume Light to a scene, choose Rendering Environment (or press the 8 key) to open the Environment dialog box. Then click the Add button in the Atmosphere rollout to open the Add Atmospheric Effect dialog box, and select Volume Light. The parameters for the volume light are presented in the Volume Light Parameters rollout.

You can also access the Volume Light effect from the Atmospheres and Effects rollout in the Modify panel when a light is selected.

CROSS-REF 

Chapter 44, "Using Atmospheric and Render Effects," covers the other atmospheric effects.

Volume light parameters

At the top of the Volume Light Parameters rollout, shown in Figure 27.14, is a Pick Light button, which enables you to select a light to apply the effect to. You can select several lights, which then appear in a dropdown list. You can remove lights from this list with the Remove Light button.

Figure 27.14: The Volume Light Parameters rollout in the Environment dialog box lets you choose which lights to include in the effect.

In the Volume section, the Fog Color swatch lets you select a color for the fog that is seen within the light. This color is combined with the color of the light. The Attenuation Color is the color the fog appears to have at a distance far from the light source. This color also combines with the Fog Color and is best set to a dark color.

The Density value determines the thickness of the fog. The Exponential option causes the density to increase exponentially with the distance. The Max and Min Light Percentage values determine the amount of glow that the volume light causes, and the Attenuation Multiplier controls the strength of the attenuation color.

You have four options for filtering shadows: Low, Medium, High, and Use Light Smp Range. The Low option renders shadows quickly but isn't very accurate. The High option takes a while but produces the best quality. The Use Light Smp Range option bases the filtering on the Sample Volume value and can be set to Auto. The Sample Volume can range from 1 to 10,000. The Low option has a Sample Volume value of 8; Medium, 25; and High, 50.

The Start and End Attenuation values are percentages of the Start and End range values for the light's attenuation. These values have an impact only if attenuation is turned on for the light.

The Noise settings help to determine the randomness of Volume Light. Noise effects can be turned on and given an Amount. You can also Link the noise to the light instead of using world coordinates. Noise types include Regular, Fractal, and Turbulence. Another option inverts the noise pattern. The Noise Threshold limits the effect of noise. Wind settings affect how the light moves as determined by the wind's direction, Wind Strength, and Phase.

Figure 27.15 shows several volume light possibilities. The left image includes the Volume Light effect, the middle image enables shadows, and the right image includes some Turbulent Noise.

Figure 27.15: The Volume Light effect makes the light visible.

Tutorial: Showing car headlights

One popular way to use volume lights is to display the headlights of cars. For this tutorial, we're going to use the Delfino Feroce 2001 car model created by Viewpoint Datalabs.

To display the headlights of a car, follow these steps:

1. Open the  Car headlights.max file from the Chap 27 directory on the DVD.

   This file includes a model of a car.

2. Select the Create Lights Standard Lights Target Spotlight menu command, and drag in the Left viewport to create a spotlight object. Select and move the spotlight and the target to be positioned to look as if a light is shining out from the left headlight.

3. Open the Modify panel, and in the Spotlight Parameters rollout, set the Hotspot value to 20 and the Falloff to 25. In the Atmospheres and Effects rollout, click the Add button, select Volume Light from the Add Atmosphere or Effect dialog box that appears, and click OK.

   Note 

   When a light is added to the scene, the default lights are automatically turned off. To provide any additional lighting, add some Omni lights above the car.

4. Select the Volume Light effect in the list within the Atmospheres and Effects rollout, and click the Setup button. The Environment dialog box opens, in which you can edit the Volume Light parameters for the newly created light. Set the Density value to 100.

5. Now create three more headlights. To do this, select both the first spotlight object and its target, and create a cloned copy by holding down the Shift key while moving it toward the right headlight. Position the other spotlights so that they shine outward from the other headlights.

Figure 27.16 shows the resulting car with its headlights illuminated.

Figure 27.16: The car now has headlights, thanks to spotlights and the Volume Light effect.

Tutorial: Creating laser beams

Laser beams are extremely useful lights. From your CD-ROM drive to your laser printer, lasers are found throughout a modern-day office. They also are great to use in fantasy and science fiction images. You can easily create laser beams using direct lights and the Volume Light effect. In this tutorial, we add some lasers to the spaceship model created by Viewpoint Datalabs.

To add some laser beams to a scene, follow these steps:

1. Open the  Spaceship laser.max file from the Chap 27 directory on the DVD.

   This file includes a spaceship model.

2. Select the Create Lights Standard Lights Directional menu command, and add a Free Direct light to the end of one of the laser guns in the Front viewport. Scale the light down until the cylinder is the size of the desired laser beam and rotate it so it points away from the laser beam.

3. With the light selected, open the Modify panel. In the Atmospheres and Effects rollout, click the Add button and double-click the Volume Light selection. Then select the Volume Light option in the list, and click the Setup button to open the Environment dialog box. Change the Fog Color to red, and make sure that the Use Attenuation Color is disabled.

4. With the direct lights added to the scene, the default lights are deactivated, so you need to add some Omni lights above the spaceship to illuminate it. To do this, select the Create Lights Standard Lights Omni menu command, and click above the spaceship in the Front view three times to create three lights. Set the Multiplier on the first light to 1.0, and position it directly above the spaceship. Set the other two lights to 0.5, and position them on either side of the spaceship and lower than the first light.

Figure 27.17 shows the resulting laser beams shooting forth from the spaceship.

Figure 27.17: You can create laser beams using direct lights and the Volume Light effect.

Using projector maps and raytraced shadows

If a map is added to a light in the Parameters rollout, the light becomes a projector. Projector maps can be simple images, animated images, or black-and-white masks to cast shadows. To load a projector map, select a light and open the Modify panel. Under the Spotlight Parameters rollout, click the Projector Map button and select the map to use from the Material/Map Browser.

Raytraced shadows take longer to render than the Shadow Maps or Area Shadows option, but the shadows always have a hard edge and are an accurate representation of the object.

Note 

You can create shadows for wireframe objects only by using raytraced shadows.

In the Shadow Parameters rollout, you can select whether shadows are computed using shadow maps or raytraced shadows. Using the latter selection lets you project a transparent object's color onto the shadow.

Tutorial: Projecting a trumpet image on a scene

As an example of a projector light, we create a musical scene with several musical notes and project the image of a trumpet on them.

To project an image onto a rendered scene, follow these steps:

1. Open the  Trumpet mask.max file from the Chap 27 directory on the DVD.

   This file includes a trumpet model shown in the maximized Left viewport. This file is used to generate a project map.

2. Choose Rendering Render (or press the F10 key) to open the Render dialog box; set the resolution to 640 × 480, and select the Left viewport. Then select the Render Elements tab, and click the Add button. Select Alpha from the Render Elements dialog box, click OK, and then click the Render button. The side view of the trumpet in the Rendered Frame Window renders along with an alpha channel rendering of the trumpet. When the rendering completes, click the Save File button in the Rendered Frame Window for the alpha channel and save the file as  trumpet mask.tif.

3. Open the  Musical notes.max file from the Chap 27 directory on the DVD.

   This file contains several musical notes created from primitive objects.

4. Select the Create Lights Standard Lights Target Spotlight menu command, and drag to create two lights in the Top viewport. Position the first spotlight to be perpendicular to the scene and to shine down on it from above.

5. Open the Modify panel; in the Advanced Effects rollout, click the Projector Map button and double-click Bitmap from the Material/Map Browser. Locate and select the  Trumpet Mask.tif file, and click Open. This projects a silhouette of a trumpet onto the scene. Use the second spotlight to light the music notes.

Figure 27.18 shows the musical notes with the trumpet projection map.

Figure 27.18: You can use projection maps to project an image in the scene, like this trumpet.

Tutorial: Creating a stained-glass window

When a light that uses raytraced shadows shines through an object with transparent materials, the Filter color of the material is projected onto objects behind. In this tutorial, we create a stained-glass window and shine a light through it using raytraced shadows.

To create a stained-glass window, follow these steps:

1. Open the  Stained glass window.max file from the Chap 27 directory on the DVD.

   This file includes a stained-glass window for a fish market (don't ask me why a fish market has a stained-glass window).

2. Select the Create Lights Standard Lights Target Spotlight menu command, and drag in the Left view from a position to the right and above the window to the window.

   This creates a target spotlight that shines through the stained-glass window onto the floor behind it.

3. In the General Parameters rollout, make sure that the On option is enabled in the Shadows section and select Ray Traced Shadows from the drop-down list. In the Shadow Parameters rollout, enable the On option for Atmosphere Shadows.

Figure 27.19 shows the stained-glass window with the colored shadow cast on the scene floor.

Figure 27.19: A stained-glass window effect created with raytraced shadows