Overview
The Gobo Light Filter is a filter placed in front of a light source that tints or blocks the emitted light. They can be applied on spot lights or area lights.
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It also permits decoupling the filter transform from the light source transform, so it becomes possible to move / rotate / scale one without the other. See Use Filter Coordinate System below.
A gobo filter in the Gaffer Object Table in front of a spot light (in white), in the Viewer.
Parameters of a Gobo Light Filter
Translate
Rotate
Scale
The object tab presents the Gobo's transform. The transform is ignored in the rendered image when Use Filter Coordinate System has been turned off in the Material parameters.
The object parameters of a gobo filter.
The material parameters of a gobo filter.
Map
An image file that is used as a filter. The image should have been processed beforehand by tdlmake.
Density
A map opacity multiplier. A density of 0 makes the map completely transparent.
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Invert
Turning this parameter on will invert the map colors.
Use Filter Coordinate SystemAnchor UseFilterCoordinateSystem UseFilterCoordinateSystem
Defines if the translation, rotation and scale specified in the Object Parameters will be applied to the filter. When this parameter is disabled, the light transform is used for the filter. Note that if the filter is set as a child of the light, then the light transform will always affect the filter. To dissociate the light transform from the filter transform and use only the later:
- Turn this parameter on;
- Unparent the filter from the light in the Gaffer Object Table;
- Set up a light filter reference as detailed above.
Scale
The scale factors applied to the range of S and T values covered by the filter, respectively. Values between 0 and 1 will appear to enlarge the map since the whole filter will cover a smaller portion of the usual texture coordinate area (from 0 to 1).
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The wrap modes were set to 'periodic' for the scale illustrations.
Offset
Specify S and T offset values applied on the map, respectively.
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The wrap modes were set to 'clamp' for the Offset illustrations.
S Wrap Mode
T Wrap Mode
Control how the area outside the filter coverage will appear. The available options are:
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| clamp | Coordinates below 0 are set to 0, and coordinates above 1 are set to 1. This will effectively repeat the map's border pixel. |
| black | Coordinates below 0 and above 1 are mapped to a black color. |
| mirror | The area outside the 0 to 1 range use coordinates that are repeated in a mirror fashion - from 0 to 1, then 1 to 0, and so on. |
| periodic | The area outside the 0 to 1 range use values from 0 to 1 repeated over again. |
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Note that the corner pixels of the map are not black, hence the checkerboard pattern on the Clamp image.