Re: [Matplotlib-users] Is there a 3D version of the quiver plot?

[Brickle M. <bri...@gm...>]

On 8/03/13 8:37 AM, Damon McDougall wrote:
> Correct me if I'm wrong, but would a 2D quiver plot on top of a
> contour plot work?  What spaces does the surface map to/from?  If your
> surface can be expressed as a function f:R^2 -> R then it's equivalent
> to look at its level sets, rather than the 3D picture.  You can then
> project the surface normals onto the plane and plot them with a 2D
> quiver plot.  If you want to keep the z-component information, then
> you could colour the arrows according to the angle they make with the
> x-y plane.
>
> Does that make sense?

My source is an image, so technically f:R^2 -> R.  Specifically I am 
using depth maps or (range image) what to visualise the 
surfaces/normals.   I was  planing on plotting the image as surface 
(hadn't work out how yet) and overlay the normal vectors.  I think a 2D 
quiver plot on top of a contour plot may provide a useful 
visualisation/interpretation of the process.

Thanks for the idea.

Brickle.
--




>
> I put the original feature request in, and I think it would be useful,
> but often I still find it easier to process two dimensional
> information.
>
> N.B.  The above will only work for *functions* f:R^2 -> R.  To
> clarify, a sphere cannot be expressed this way, because the resulting
> mapping would be multivalued.  Using this method, two distinct surface
> normals may have the same colour.
>
> Hope that makes sense.
>
> Best wishes,
> Damon
>
>> Brickle.
>> --
>>
>>
>> On 8/03/13 5:43 AM, Benjamin Root wrote:
>>
>>
>>
>> On Thu, Mar 7, 2013 at 4:25 PM, Eric Firing <ef...@ha...> wrote:
>>> On 2013/03/07 9:19 AM, Benjamin Root wrote:
>>>>
>>>> On Thu, Mar 7, 2013 at 2:14 PM, Brickle Macho <bri...@gm...
>>>> <mailto:bri...@gm...>> wrote:
>>>>
>>>>      I have a list of surface normals I would like to plot.  Is there a
>>>> way
>>>>      to plot a 3D vectors in matplotlib similar to how quiver plots 2D
>>>>      vectors?
>>>>
>>>>
>>>> Not at this time, but that would make a great feature request!  I think
>>>> the current roadblock to such a function is a bug with converting 2d
>>>> arrow objects into 3d arrows.
>>> Quiver uses a PolyCollection, and I see that there is a Poly3DCollection.
>>>
>>> Eric
>>>
>>>> Ben Root
>>>
>> Took a bit of digging, but I knew I remembered this question before:
>>
>> http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CDMQFjAA&url=http%3A%2F%2Fmatplotlib.1069221.n5.nabble.com%2F2D-Quiver-in-Axes3D-td27944.html&ei=Pwk5UfGdLufv0QHuroD4BA&usg=AFQjCNEqlWv2vY5l2IPcje-g6B0U21wDNw&bvm=bv.43287494,d.dmQ
>>
>> And the feature request is here:
>> https://github.com/matplotlib/matplotlib/issues/1026
>>
>> In the thread I pointed out a bug that I encountered.  I really hope I get
>> some free time soon so that I can work on the various feature requests in
>> mplot3d.
>>
>> Cheers!
>> Ben Root
>>
>>
>>
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