Transmit

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Overview

 

Projects an image through a refractive surface and traces where the light ends up.  This node can be thought of as a projector where the lens has been replaced with a warped piece of glass.  This produces patterns that are similar to those produced by the Caustics node.

 

Like the Refract node, Transmit is able to warp an image by passing it through a refractive surface.  However, unlike nodes such as Refract and Distort where each point in the resulting image derives its color from exactly one point in the source image, the Transmit node can fold images back over themselves in such a way that a single point in the result can derive its color from any number of source points.

 

 

Transmit Example

The Transmit node can distort images by folding them back over themselves.

 

 

 

Inputs

 

 

Input

Description

Original

The original image that is to be distorted by projecting it through a refractive surface.

Heightmap

The red channel of this input is used as a height map for constructing the refractive surface.

 

 

 

Properties

 

 

Transmit Diagram

 

 

Property

Description

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.

Elevation

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.

Sample Density

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

Sample Pattern

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

 

Regular

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

Random

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.

Blend Mode

Specifies the technique used to combine multiple light rays striking the same point of the observation screen:

 

Add

The brightness of converging light rays are added.  This is the technique used by Mother Nature, but can result in some very bright spots.

Screen

The brightness of converging light rays has less of an effect as the number of rays striking the same point increases.  This technique does not imitate nature, but will help avoid overly bright spots.

 

 

 


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