Chessboard irradiation pattern

Purpose: to show usage of python preparser with meta-input code.

Note the nested for loops and the conditional if.

Meta-input file

# create a 'chessboard' irradiation pattern by displacing the field
# use a single spot with square cross-section

nprim=1e4

def: side = 5
def: spotSize = 1
def: spotSpacing = spotSize
def: nspot = int(side/spotSpacing)

pb: 1 0 ; Xsec = box ; FWHM = $spotSize

region: phantom ; L=[${side*1.5},${side*1.5},1] ; voxels = [200,200,1] ; pivot=[0.5,0.5,0]

for(ix in range(nspot+1))< # control points in x
    for(iy in range(nspot+1))< # control points in y

        if(mod(ix,2)==mod(iy,2))< # choose alternate squares
            def: x = -side/2 + ix*spotSpacing
            def: y = -side/2 + iy*spotSpacing
            transform: field_0 move_to $x $y -50
            deliver: all
        if>
    for>
for>

The python preparser generates the following input file (look into out/log/run.inp):

nprim=1e4
pb: 1 0 ; Xsec = box ; FWHM = 1
region: phantom ; L=[7.5,7.5,1] ; voxels = [200,200,1] ; pivot=[0.5,0.5,0]
transform: field_0 move_to -2.5 -2.5 -50
deliver: all
transform: field_0 move_to -2.5 -0.5 -50
deliver: all
transform: field_0 move_to -2.5 1.5 -50
deliver: all
transform: field_0 move_to -1.5 -1.5 -50
deliver: all
transform: field_0 move_to -1.5 0.5 -50
deliver: all
transform: field_0 move_to -1.5 2.5 -50
deliver: all
transform: field_0 move_to -0.5 -2.5 -50
deliver: all
transform: field_0 move_to -0.5 -0.5 -50
deliver: all
transform: field_0 move_to -0.5 1.5 -50
deliver: all
transform: field_0 move_to 0.5 -1.5 -50
deliver: all
transform: field_0 move_to 0.5 0.5 -50
deliver: all
transform: field_0 move_to 0.5 2.5 -50
deliver: all
transform: field_0 move_to 1.5 -2.5 -50
deliver: all
transform: field_0 move_to 1.5 -0.5 -50
deliver: all
transform: field_0 move_to 1.5 1.5 -50
deliver: all
transform: field_0 move_to 2.5 -1.5 -50
deliver: all
transform: field_0 move_to 2.5 0.5 -50
deliver: all
transform: field_0 move_to 2.5 2.5 -50
deliver: all

Results:

here the technique is to keep fixed the phantom and move the beam at each spot

The resulting irradiation pattern on the phantom looks like:

Chessboard-like irradiation pattern (lin scale)