# Mapping to spherical coordinates (sphericalcoordsvolume)#

Parameter

Type

Description

Flags

volume

volume

Nested volume plugin whose data is to be mapped to spherical coordinates.

rmin

float

Radius for the inner limit of the spherical shell, relative to the unit sphere. Default: 0

rmax

float

Radius for the outer limit of the spherical shell, relative to the unit sphere. Default: 1

fillmin

float

Constant value to return for points such that $$r < r_\mathrm{min}$$. Default: 0

fillmax

float

Constant value to return for points such that $$r_\mathrm{max} < r$$. Default: 0

to_world

transform

Specifies an optional 4x4 transformation matrix that will remap local spherical coordinates from the unit sphere (which covers the [-1, 1]³ cube) to world coordinates.

This plugin addresses volume data in spherical coordinates. In practice, it maps the texture coordinates of a nested volume plugin to the unit sphere using the following correspondance:

$\begin{split}x \in [0, 1] & \leftrightarrow r \in [r_\mathrm{min}, r_\mathrm{max}] \\ y \in [0, 1] & \leftrightarrow \theta \in [0, \pi] \\ z \in [0, 1] & \leftrightarrow \phi \in [-\pi, \pi]\end{split}$

where $$r$$ is the radius of the considered point in the unit sphere. For angles, the default mathematical convention is used: $$\theta$$ is the zenith angle with respect to the $$+Z$$ unit vector, and $$\phi$$ is the azimuth angle with respect to the $$(+X, +Z)$$ plane.

Note

When using this plugin with a nested gridvolume, the data layout remains unchanged (i.e. zyxc will be interpreted as φθrc).