On Thu, Nov 11, 2010 at 3:55 PM, James Davidheiser <
jdavidhei...@unisynmedical.com> wrote:
> *From:* ben.v.r...@gmail.com [mailto:ben.v.r...@gmail.com] *On Behalf Of
> *Benjamin Root
> *Sent:* Thursday, November 11, 2010 12:20 PM
> *To:* James Davidheiser; Matplotlib Users
>
> *Subject:* Re: [Matplotlib-users] Axes labels crooked using mplot3d in WX
>
>
>
> On Thu, Nov 11, 2010 at 12:20 PM, Benjamin Root <ben.r...@ou.edu> wrote:
>
> On Thu, Nov 11, 2010 at 9:31 AM, James Davidheiser <
> jdavidhei...@unisynmedical.com> wrote:
>
>
>
>
>
> *From:* ben.v.r...@gmail.com [mailto:ben.v.r...@gmail.com] *On Behalf Of
> *Benjamin
> Root
> *Sent:* Thursday, November 11, 2010 8:19 AM
> *To:* James Davidheiser
> *Cc:* matplotlib-users@lists.sourceforge.net
> *Subject:* Re: [Matplotlib-users] Axes labels crooked using mplot3d in WX
>
>
>
> On Thu, Nov 11, 2010 at 8:49 AM, James Davidheiser <
> jdavidhei...@unisynmedical.com> wrote:
>
> *From:* ben.v.r...@gmail.com [mailto:ben.v.r...@gmail.com] *On Behalf Of
> *Benjamin
> Root
>
>
>
> On Wed, Nov 10, 2010 at 3:12 PM, unij <jdavidhei...@unisynmedical.com>
> wrote:
>
>
> I'm trying to use mplot3d in a Wx based application, and most things seem
> to
> be working fine. The one issue that keeps tripping me up is that the axes
> labels are drawn at a weird angle. If I do the same type of plot without
> using wx, then this problem goes away. I am completely stumped as to where
> to even begin looking to fix this problem, so I would appreciate any
> pointers you can give me.
>
> I've attached a screenshot showing what I am talking about - a simple plot
> where the axes labels look strange.
>
>
> http://old.nabble.com/file/p30184616/mplot3d.jpg
>
>
> I can reproduce the weird angle issue, but I can't seem to find a backend
> where it doesn't occur. Could you run "import matplotlib; print
> matplotlib.get_backend()" to determine which backend you are using when
> everything looks ok? Also, could you report the output of
> "matplotlib.__version__"?
>
> If it happens for all backends then the problem is in mplot3d/axis3d.py.
> Unfortunately, the code there is a little light on commenting, but i don't
> notice any glaring mathematical error off the bat.
>
> Ben Root
>
>
>
>
>
>
>
> That’s actually a really good point and something I didn’t explain well – I
> didn’t go out of my way to test with other backends, but rather I tried it
> by recreating the plot independently of my GUI, creating the same plot
> using pyplot, following the example in scatter3d_demo.py from the
> sourceforge demos page. If I then import matplotlib and check the backend,
> I get that it’s TkAgg, but I’m not sure whether that backend is actually
> being used – is it?
>
>
>
> I did just try changing between Wx and WxAgg for the backends, and the
> positions of the labels definitely move around in weird ways between the
> two, so I think I’m now even more confused than I was before.
>
>
>
> James
>
> The difference between a gui kit like Wx and its Agg equivalent is probably
> expected. Agg renderers bring additional capabilities and functionality
> with respect to rendering special vector-based graphics such as fonts. For
> example, while examining this bug, I noticed that the GTK backend can only
> represent fonts with either a 0 degree rotation, or 90 degree rotation,
> while the GTKAgg doesn't have that limitation.
>
> I have tested Wx, WxAgg, GTK, GTKAgg, QTAgg, QT4Agg, and TkAgg and have
> found them all to be rotating the text incorrectly. GTK doesn't rotate at
> all, and emits an error (I wonder if we can catch this and perform an
> appropriate failback?). Wx does not appear to be performing the translation
> step properly, causing the label to appear on top of the tick labels. The
> other backends all seem to have similar results.
>
> I wonder if the calculation for the text angle is off because maybe it is
> not using all 3 dimensions? In other words, the text appear to fail to take
> into account depth perception. I will take another peek at the code and see
> what I can figure out.
>
> Ben Root
>
>
>
>
>
> I also noticed that the problem is dependent on window / frame dimensions –
> resize the frame, and the angle changes. For nearly square windows, the
> angles are almost correct, but as you go to more rectangular aspect ratios,
> the text gets skewed. I’m guessing that means the error has something to do
> with the assumptions the code is making about how the window is scaled,
> which break down when you’re not in a square.
>
>
>
> James
>
> Astute observation. Digging further, I have noticed that the source of the
> problem is that the angle given to a text object is relative to the display
> coordinate system. So, no matter how one resizes the figure window, the
> text angle is *always* the same. When the aspect ratio is square, then
> everything lines up right. I am going to look into making text objects
> aware of transforms for rotation purposes to fix this problem.
>
> Ben Root
>
>
> Success! There were two separate issues at play here. First, there was a
> slight mistake in calculating the 2D label location from the 3D location of
> the axis mid-point. This caused labels to not appear centered along the
> axis. This has been a long-standing bug that is now resolved by my patch.
>
> The second issue is that when a Text object is given a rotation (in this
> case, by the Axis3D object). The rotation angle that a Text object expects
> is assumed to be for the display coordinate system. The angle that was
> calculated was for the axes coordinate system, which caused problems when
> the axes display aspect ratio was not equal (or square?). I might be mixing
> up some of the details because of the assumptions that are made in mplot3d.
>
> A permanent solution would be to address the issue of how the rotation
> angle should be interpreted in a Text object. I can imagine several cases
> in 2D plots where the current behavior is undesirable.
>
> However, for the purposes of mplot3d, because of its architecture, this
> angle gets recalculated for every re-draw anyway, so I decided to just
> properly calculate the angle at that point instead. I also made sure that
> the text object knows that I want its anchor point to be in the center of
> the text object for both horizontal and vertical alignment to make sure the
> object gets displayed properly.
>
> I have attached the patch here. Feel free to try and break the alignment
> in case I missed something.
>
> Ben Root
>
>
>
>
>
> Thanks very much – the patch seems to work well and the axes look much
> better now.
>
>
>
> I have a followup question, which is more of a generic mplot3d question –
> is there an easy way to tell mplot3d to add more space between the axes
> labels and the axes? I have some graphs where the number labels on the
> tickmarks overlap with the axes labels, and it would be nice to easily add a
> bit of room to clean everything up.
>
>
>
> James
>
Easy? Not really... this is going to be one of my next todos to make parts
of Axes3D to be more user-configurable. Right now, a lot of parameters such
as the panel colors, element spacing and such are all hard-coded
(particularly in axis3d.py). If you are feeling adventurous and really need
a fix, line 223 of axis3d.py reads as "labeldeltas = 1.3 * deltas" where you
could tweak the "1.3" number to bring the axis label closer/farther from the
axis. You can also tweak the "0.6" in line 278 ("labeldeltas = [0.6 * x for
x in deltas]") to bring the tick labels closer/farther from the axis.
I hope that helps, and I am glad the axis label looks much better now.
Ben Root
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