
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_{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 
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 
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_{side}=256 map.
MODULES & ROUTINESThis 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 ROUTINESThis 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 of a spherical triangle defined by 3 vertices
Eric Hivon
20100618

