Re: [Yt-dev] Axis-aligned normal vectors in the camera

Hi, I've never worked with a North vector, but I know Andy Cunningham has, and I know he patched the source to allow some flexibility with this. I don't remember exactly what he did, but you might consider asking him. j On Thu, Jul 29, 2010 at 8:14 AM, Matthew Turk wrote:

Hi Rick,

I think I agree with your assessment, it's in the setup_normalized_vectors.  What I think is happening is that my guess for a north vector (if unsupplied, and I don't know about anybody else but I never supply a north vector ...) is resulting in it getting zero for the other unit vectors.  Would you be able to see what the value of cam.north_vector is in your script?

What we might also want to do is just add some jitter to the estimate for a North vector, which might be able to help it.  Inside setup_normalized_vectors, if you change the original:

       if north_vector is None:            vecs = na.identity(3)            t = na.cross(normal_vector, vecs).sum(axis=1)            ax = t.argmax()            north_vector = na.cross(vecs[ax,:], normal_vector).ravel()

to something like:

       if north_vector is None:            vecs = na.identity(3)            t = na.cross(normal_vector + [1e-9, 0.0, 0.0], vecs).sum(axis=1)            ax = t.argmax()            north_vector = na.cross(vecs[ax,:], normal_vector).ravel()

it might have some (good?) effect.  I think Sam has an alternate mechanism for estimating a north vector that might fix this, too..

-Matt On Thu, Jul 29, 2010 at 7:58 AM, Rick Wagner wrote:

...

Good Morning,

I've been trying out the volume render, with a lot of success. However, while I was starting to work on rotating the view, I found the normal vectors aligned with x, y or z would create blank images. After reading what was printed on the console, I saw that the volume being rendered had zero width in two dimensions:

yt         INFO       2010-07-29 08:31:28,740 Traversing 17583 bricks between [ 0.45  0.5   0.5 ] and [ 0.55  0.5   0.5 ]

I tried looking into extension/volume_rendering/camera.py last night, in particular _setup_normalized_vectors, but the body and mind were weak. I'll keep trying, but if anyone has suggestions, or corrections to my method, they would be appreciated.

Rendering script at http://paste.enzotools.org/show/958/

Thanks, Rick

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