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).