Hi, I am trying to create a mask from a shapefile containing vectors (not polygons) using IDLanROIGroup->ComputeMask. I get as far as creating the ROI group containing all my vector data from the shapefile, then I apply ComputeMask but the result is an empty mask... why is this? could you spot if I am missing anything? - Thanks! Here is my code: function Rasterize_vector_data, path_vector_data myShape = OBJ_NEW('IDLffShape', path_vector_data) myShape->GetProperty, N_ENTITIES=num_vectors size_mask = [1071, 1390] ;init the object where all vectors are going to be stored as ROI roi_group = OBJ_NEW('IDLanROIGroup') ;for each vector in the file, get the vertices and create a mask vect = 0 for vect = 0L, num_vectors-1 do begin entity = myshape->GetEntity(vect, /ATTRIBUTES) vertices = *entity.VERTICES roi_vector = OBJ_NEW('IDLanROI', vertices) ;Add the vector to the group roi_group->Add, roi_vector endfor ;create mask from group mask = roi_group->ComputeMask(DIMENSIONS=size_mask, MASK_RULE=0, INITIALIZE=0) RETURN, mask end