query_triangle

Routine to find the index of all pixels enclosed in a spherical triangle described by its three vertices. The output indices can be either in the RING or NESTED scheme

Location in HEALPix directory tree: src/f90/mod/pix_tools.F90 

FORMAT

call query_triangle( nside, v1, v2, v3, listpix, nlist[, nest, inclusive] )

ARGUMENTS

name&dimensionality	kind	in/out	description
nside	I4B	IN	the $N_{\mathrm{side}}$ parameter of the map.
v1(3)	DP	IN	cartesian vector pointing at the triangle first vertex.
v2(3)	DP	IN	cartesian vector pointing at the triangle second vertex.
v3(3)	DP	IN	cartesian vector pointing at the triangle third vertex.
listpix(0:*)	I4B/ I8B	OUT	the index for all pixels enclosed in the triangle. Make sure that the size of the array is big enough to contain all pixels.
nlist	I4B/ I8B	OUT	The number of pixels listed in listpix.
nest (OPTIONAL)	I4B	IN	The pixel indices are in the NESTED numbering scheme if nest=1, and in RING scheme otherwise.
inclusive (OPTIONAL)	I4B	IN	If set to 1, all the pixels overlapping (even partially) with the triangle are listed, otherwise only those whose center lies within the triangle are listed.

EXAMPLE:

call query_triangle(256,(/1,0,0/),(/0,1,0/),(/0,0,1/),listpix,nlist)

Returns the RING pixel index of the (98560) pixels in the octant ($x,y,z>0$) in a $N_{\mathrm{side}}=256$ map.

MODULES & ROUTINES

This section lists the modules and routines used by query_triangle.

in_ring

routine to find the pixels in a certain slice of a given ring.

intrs_intrv

routine to compute the intersection of 2 intervals on a circle

ring_num

function to return the ring number corresponding to the coordinate $z$

vect_prod

routine to compute the vectorial product of two 3D vectors

RELATED ROUTINES

This section lists the routines related to query_triangle

pix2ang, ang2pix

convert between angle and pixel number.

pix2vec, vec2pix

convert between a cartesian vector and pixel number.

query_disc, query_polygon,

query_strip, query_triangle

render the list of pixels enclosed respectively in a given disc, polygon, latitude strip and triangle

surface_triangle

computes the surface in steradians of a spherical triangle defined by 3 vertices