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Based on the work of [1] I obtained the depth data of my scene as shown in the code bellow: 

scene.use_nodes = True
tree = scene.node_tree
links = tree.links

# create input render layer node
rl = tree.nodes.new('CompositorNodeRLayers')    

# create output node
v = tree.nodes.new('CompositorNodeViewer')   
v.use_alpha = False

# Links
links.new(rl.outputs['Z'], v.inputs[0]) # link Z to output

bpy.ops.render.render()

# get viewer pixels
pixels = bpy.data.images['Viewer Node'].pixels
# size is always width * height * 4 (rgba)
pixels = np.array(pixels)[::4]

ix = scene.render.resolution_x
iy = scene.render.resolution_y
depth = np.zeros((ix/2,iy/2))

for i in range(0, int(round(ix/2))):
 for k in range(0, int(round(iy/2))):
     depth[i,k] = pixels[i+k]     

np.save('...\\outfile.npy', depth)

I set up the nodes, forward the z-data to the output node, render and save the pixels as an array. Since I use depth data instead of RGBA, I only use every 4-th element in the array since the other 3 ones are equal. Further, I use the dimensions of the image to setup a ndarray with numpy (depth) wich I save to an .npy file finally. Somewhere in this part I make a mistake since following code (from commandline) generates a somehow weird looking plot (shown below as well) 

from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt
import numpy as np

data = np.load('...\\outfile.npy')
x, y = np.mgrid[:data.shape[0], :data.shape[1]]
fig = plt.figure()
ax = fig.add_subplot(1,1,1,projection="3d")
surf=ax.plot_surface(x,y,data)
plt.show()

For a centered cube I get the following outcome:

Plot of depth data for a scene with a centered cube

So I hope somebody can give me a hint on where to look exactly for the error, and also I would be very thankfull for coding and style tips. I also found similar posts, but no one where the obtained data is visualized.

[1] https://ammous88.wordpress.com/2015/01/16/blender-access-render-results-pixels-directly-from-python-2/

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  • $\begingroup$ Further investigation showed, that the outcome is of by one each vector in the xy plane. Meaning that the first row is done properly, the second one is shifted to the left by one entry, the second row is shifted to the left by two entries,..... This happens already in the code. $\endgroup$
    – mrks
    Commented Dec 7, 2016 at 9:31
  • $\begingroup$ Please share a screenshot of the 3D mode. $\endgroup$
    – Mo Hossny
    Commented Jan 12, 2017 at 1:51

1 Answer 1

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the line

depth[i,k] = pixels[i+k]

seems off to me, it seems as if you need to transform your indices between the 2d depth array and the flat 1d pixels array like:

depth[i,k] = pixels[i*int(round(ix/2))+k]

where the index i offsets multiples of the length a whole row into the array, and k additionally offsets into each element of it.

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