|
query_polygon
Routine to find the index of all pixels enclosed in a polygon. The polygon should be convex,
or have only one concave vertex. The edges should not intersect each other.
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_polygon(
nside, vlist, nv, listpix, nlist [, nest, inclusive]
)
ARGUMENTS
| name & dimensionality |
kind |
in/out |
description |
|---|
| |
|
|
|
|
nside |
I4B |
IN |
the Nside parameter of the map. |
| vlist(1:3,0:*) |
DP |
IN |
cartesian vector pointing at polygon
respective vertices. |
| nv |
I4B |
IN |
number of vertices, should be equal to 3 or larger. |
| 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 polygon are listed, otherwise only those whose
center lies within the polygon are listed. |
EXAMPLE:
real(dp), dimension(1:3,0:9) :: vertices
vertices(:,0) = (/0.,0.,1./) ! +z
vertices(:,1) = (/1.,0.,0./) ! +x
vertices(:,2) = (/1.,1.,-1./) ! x+y-z
vertices(:,3) = (/0.,1.,0./) ! +y
call query_polygon(256,vertices,4,listpix,nlist,nest=0)
Returns the RING pixel index of all pixels in the polygon with vertices of
cartesian coordinates (0,0,1), (1,0,0), (1,1,-1) and (0,1,0) in a Nside=256 map.
MODULES & ROUTINESThis section lists the modules and routines used by query_polygon.
-
isort
- routine to sort integer number
-
query_triangle
- render the list of pixels enclosed
in a given triangle
-
surface_triangle
- computes the surface of a spherical triangle defined by 3 vertices
-
vect_prod
- routine to compute the vectorial product of two 3D vectors
RELATED ROUTINESThis section lists the routines related to query_polygon
-
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
Eric Hivon
2010-06-18
|
|
