Create a volumic light effect with a constant start and end falloff


Table of contents

Summary

You are looking for a way to create a Volumic Light effect with a constant start and end falloff.

You also would like to eliminate the "hotspot" effect that appears at the cusp of the light's start falloff when the spotlight is facing the camera lens.


Steps

  • Load a spotlight: Get > Light Spot
  • Select the spotlight and apply a Volume property to the light by selecting Get > Property > Volumic from the Render toolbar.
  • Open an explorer and select the Show All Nodes filter.
  • Expand the Spot_Root node, select the Spot node and open the spotlight's master Property Page by right-clicking All Properties.
  • In the spotlight's master Property Page, access the soft_light tab and edit the following Light Attenuation properties:


Light Falloff

Activated

Mode

Linear

Start Falloff

1000.000

End Falloff

1000.000


Note that the Start Falloff value must be similar to the End Falloff value. To define adjoining Start Falloff and End Falloff values is what essentially creates the constant Volume Falloff since it simply eliminates the falloff effect.

  • Click the Volumic tab of the same Property Page and edit the following settings:


Enabled

Activated

Map Size

100

Reflectance

10.000

Min Distance

0.000

Force Volume Shadows

Disabled

Transparent

Disabled


Important: Reflectance parameter affects the brightness of the volume. Be careful when changing this value, as increasing the value even slightly, can saturate the colour of the volume. Note also that changing the light's Intensity value will not affect the volume's colour.

Edit the Global Volumic Properties

  • In the explorer, select the Volume Properties node and either double-click or hit the Enter key to open the Volumic Properties Property Page
  • Keep the Step value's default setting of 0.5 and set the value for the Max Ray Length parameter to 200.000
The Global Volumic Properties are invaluable when working with volumic lights. One parameter that cannot be ignored is the Max Ray Length, as this parameter determines the sampling distance of the volume. When in doubt, set the Max Ray Length to a value greater than the light's End Falloff value. Think of the Max Ray Length as a kind of of bounding box for the volume.

Example Image:

Image:vol_light.jpg

This page was last modified 05:50, 15 Dec 2010.
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