Merge pull request yt-project#3782 from neutrinoceros/fix_cyl_pix

BUG: fix pixelize_cylinder

yt/utilities/lib/pixelization_routines.pyx

@@ -525,7 +525,8 @@ def pixelize_cylinder(np.float64_t[:,:] buff,
 
  cdef np.float64_t x, y, dx, dy, r0, theta0
  cdef np.float64_t rmax, x0, y0, x1, y1
- cdef np.float64_t r_i, theta_i, dr_i, dtheta_i, dthetamin
+ cdef np.float64_t r_i, theta_i, dr_i, dtheta_i
+ cdef np.float64_t r_inc, theta_inc
  cdef np.float64_t costheta, sintheta
  cdef int i, pi, pj
 
@@ -558,9 +559,9 @@ def pixelize_cylinder(np.float64_t[:,:] buff,
  rbounds[0] = 0.0
  if y0 < 0 and y1 > 0:
  rbounds[0] = 0.0
- dthetamin = dx / rmax
- for i in range(radius.shape[0]):
+ r_inc = 0.5 * fmin(dx, dy)
 
+ for i in range(radius.shape[0]):
  r0 = radius[i]
  theta0 = theta[i]
  dr_i = dradius[i]
@@ -569,15 +570,15 @@ def pixelize_cylinder(np.float64_t[:,:] buff,
  if r0 + dr_i < rbounds[0] or r0 - dr_i > rbounds[1]:
  continue
  theta_i = theta0 - dtheta_i
- # Buffer of 0.5 here
- dthetamin = 0.5*dx/(r0 + dr_i)
+ theta_inc = r_inc / (r0 + dr_i)
+
  while theta_i < theta0 + dtheta_i:
  r_i = r0 - dr_i
  costheta = math.cos(theta_i)
  sintheta = math.sin(theta_i)
  while r_i < r0 + dr_i:
  if rmax <= r_i:
- r_i += 0.5*dx
+ r_i += r_inc
  continue
  y = r_i * costheta
  x = r_i * sintheta
@@ -586,8 +587,8 @@ def pixelize_cylinder(np.float64_t[:,:] buff,
  if pi >= 0 and pi < buff.shape[0] and \
  pj >= 0 and pj < buff.shape[1]:
  buff[pi, pj] = field[i]
- r_i += 0.5*dx
- theta_i += dthetamin
+ r_i += r_inc
+ theta_i += theta_inc
 
 cdef int aitoff_Lambda_btheta_to_xy(np.float64_t Lambda, np.float64_t btheta,
  np.float64_t *x, np.float64_t *y) except -1: