New issue 942: volume rendering blank if draw_coordinate_vectors() is on but draw_domain() is not used. https://bitbucket.org/yt_analysis/yt/issue/942/volume-rendering-blank-if Michael Zingale: If I do a volume rendering with the draw_coordinate_vectors() on, but not the draw_domain(), we don't get any image. Here's a sample script that can be used with the maestro_subCh_plt00248.tgz file on the data page: ``` #!/usr/bin/env python # this is for the wdconvect problem import matplotlib matplotlib.use('agg') # this example comes from # http://yt-project.org/doc/visualizing/volume_rendering.html import math import sys import numpy as np import os import pylab import yt import yt.visualization.volume_rendering.api as vr def doit(plotfile): ds = yt.load(plotfile) cm = "coolwarm" field = ('boxlib', 'radial_velocity') vals = [-5.e6, -2.5e6, -1.25e6, 1.25e6, 2.5e6, 5.e6] sigma = 1.e5 # select a sphere center = (0, 0, 0) R = (5.e8, 'cm') dd = ds.sphere(center, R) # Instantiate the ColorTransferfunction. tf = vr.ColorTransferFunction((min(vals), max(vals))) # Set up the camera parameters: center, looking direction, width, resolution c = np.array([0.0, 0.0, 0.0]) L = np.array([1.0, 1.0, 1.0]) L = np.array([1.0, 1.0, 1.2]) W = 1.5*ds.domain_width N = 720 north=[0.0,0.0,1.0] for v in vals: tf.sample_colormap(v, sigma**2, colormap=cm) #, alpha=0.2) # alternate attempt ds.periodicity = (True, True, True) # Create a camera object cam = vr.Camera(c, L, W, N, transfer_function=tf, ds=ds, data_source=dd, no_ghost=False, north_vector=north, fields = [field], log_fields = [False]) #cam.zoom(3) # make an image im = cam.snapshot() # add an axes triad -- note if we do this, we HAVE to do draw # domain, otherwise the image is blank (likely a bug) cam.draw_coordinate_vectors(im) # add the domain box to the image: #nim = cam.draw_domain(im) # increase the contrast -- for some reason, the enhance default # to save_annotated doesn't do the trick (likely a bug) #max_val = im[:,:,:3].std() * 4.0 #nim[:,:,:3] /= max_val f = pylab.figure() pylab.text(0.2, 0.85, "{:.3g} s".format(float(ds.current_time.d)), transform=f.transFigure, color="white") cam._render_figure = f # save annotated -- this added the transfer function values, # but this messes up our image size defined above cam.save_annotated("{}.png".format(os.path.normpath(plotfile)), im, dpi=145, clear_fig=False) if __name__ == "__main__": # Choose a field plotfile = "" try: plotfile = sys.argv[1] except: sys.exit("ERROR: no plotfile specified") doit(plotfile) ```