Table 1.

Compositing methods in FluoRender

Type	Equationa	Description	Use
Front-to-back	$C_{\mathit{out}}=\left(1-{\alpha }_{\mathit{dest}}\right)\bullet C_{\mathit{source}}+C_{\mathit{dest}}$	Blends semitransparent layers from front to back. Also used for ray casting	Direct volume rendering (DVR) for one channel
Back-to-front	$C_{\mathit{out}}={\alpha }_{\mathit{source}}\bullet C_{\mathit{source}}+\left(1-{\alpha }_{\mathit{source}}\right)\bullet C_{\mathit{dest}}$	Blends semitransparent layers from back to front	Layered channel- intermixing mode
Addition	$C_{\mathit{out}}=C_{\mathit{source}}+C_{\mathit{dest}}$	Sums input and existing intensity values	Composite channel- intermixing mode; compositing operations between slices in depth mode; visualization of selected structures
Maximum intensity	$C_{\mathit{out}}=\mathit{MAX}\left(C_{\mathit{source}},C_{\mathit{dest}}\right)$	Finds the maximum intensity value from the input and existing values	MIP rendering for one channel
Multiplication	$C_{\mathit{out}}=C_{\mathit{source}}\bullet C_{\mathit{dest}}$	Multiplies the intensity value of the input by the existing value. Also called modulation	Shading and shadow effects

^aIn the equations, $C_{\mathit{out}}$, $C_{\mathit{source}}$, and $C_{\mathit{dest}}$ denote the output, input, and existing color values, respectively; $\alpha$ is the opacity value