The optional Position slave component of a Loop outputs the 'completion percentage' of the loop as a normalized number of the current loop iteration. The iteration number is normalized into the range of 0:1 then converted to color via interpolation between two colors defined by the Start and End inputs.
This slave component must be connected to the subtree of its master's Accumulator input through a subtree of components, not directly. The connection between this slave component and its master Loop component must not be routed through any bitmap-based components.
For general information about slave components, see Slave components.
Start and End: Map Input (HDR)
These inputs define the color range of the Position output. Technically, they are used for converting the normalized iteration number into a color by using this number as a percentage of interpolation between Start and End colors. These inputs can accept HDR colors.
Iteration (preview):
This slider allows you to preview the output of this slave component for any loop iteration, which is useful for creating and debugging the loop subtree. The values of the Iteration (Preview) sliders are synchronized across all slave components of Loop. The maximum value for this slider is defined by the Iterations input of the master Loop component.
Technically, this slider defines the output of the slave component in situations when it is sampled by any component which is not its master.
