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This node simulates the passage of light rays through a refractive surface, such as water, in order to calculate where the light will accumulate on a screen beyond the surface.  The bright spot that is created by a magnifying glass that is under the sun is an example of caustics.  This node has similarities to the Transmit node.



Caustics Nodes

Caustics can be used to simulate the light patterns

appearing at the bottom of a swimming pool.






This node accepts one input, which it uses as a height map for constructing the three-dimensional surface that the light rays are passed through.  Only the red channel of the input is used.







Caustics Diagram





Refractive Index

Specifies the refractive index of the surface.  The refractive index describes the degree to which a surface will bend light rays passing through it.


Controls the distance between the refractive surface and the observation screen, as shown in the previous illustration.

Height Factor

Modifies the bumpiness of the refractive surface, as shown in the previous illustration.


Controls the brightness of the light source.

Sample Density

Modifies the number of virtual light rays used to simulate the caustics.  This property has a significant impact on render time, so it should be set to the minimum value that yields acceptable results.

Sample Pattern

Specifies the starting pattern of the virtual light rays used to simulate the caustics:



The light rays begin arranged in a regular grid.  This arrangement can yield smoother results, but can also produce unwanted track patterns.


The light rays begin arranged randomly.  This arrangement avoids the unwanted track patterns that the Regular arrangement described above can produce, but it tends to require a higher Sample Density in order to achieve the same degree of smoothness.


When this property is left with its default values of 0, the virtual light rays begin perpendicular to the refractive surface and observation screen.  Moving the values away from zero, either positively or negatively, causes the light rays to begin slanted.




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