Strip Lights

So you thought area lights were not possible in MAX without any 3rd - party plug-ins? Well you would be wrong. It is possible to create area lights such as strip lights using the motion blur effects within video post. The image below was created using only 1 omni light, and no plug-ins, yet it appears to have been created using a volume light. The effect is achieved by using video post to render the light in different positions along the tube, and use motion blur to blend the resulting shadows together.

The first task is to create a basic scene with a few standard primitives, as in the picture, including a ground plane for receiving shadows. Apply a material to all of the objects; I used a reflective material, but you can use other materials to reduce the rendering times.

The next stage is to add the actual strip light. Place a cylinder in the scene to represent the light, and assign a self-illuminating white material to it. Ensure that the cylinder does not receive or cast shadows by looking within the properties. Now insert a helix, which is the same length and diameter as the cylinder, and increase the turns to 10. The helix will form the path, which the light will follow. Now place an omni light in the scene, with a multiplier of 2. Set the shadows to Ray Traced Shadows, and ensure the light is casting shadows. Add a path constraint to it. Use the helix as the path, and scrub the timeline to see the light move along the path.

At the moment, the light takes 100 frames to complete its motion. We want the light to get from one end of the cylinder to the other over just 1 frame, so drag its last key from frame 100 to frame 1. Now open track view, and navigate to the omni light properties. Click on the 'Param Curve Out-Of-Range Types' button for the Percent and select loop for both keys.

Almost there. The last thing to do is open up Video Post. Click on 'Add Scene Event' and add your camera view, or perspective depending on the view you wish to render. Turn Scene Motion Blur on, and set this to 1 frame. Set the Sub Divisions to 50 and the dither to 100% and that's it. Click OK, and hit the Execute Sequence button.

This technique takes a long time to render, especially for large, complex scenes. It is best used for still frames, but it could be adapted to cover animations. This technique could also be used for other types of volume lights, providing that a uniform path can be formed along its surface; Ring lights are a good example here.

Now go away and try it for yourself. If you have any questions, please feel free to email me, or post a topic in the forum.

This tutorial was adapted from the Q and A section of 3D world Magazine. Please show your support by going out and buying a copy, and visiting the website. [W]

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