[x3d-public] A few suggestions from the Python API (x3d.py)
John Carlson
yottzumm at gmail.com
Wed Feb 9 15:18:09 PST 2022
Moritz, I’m not sure if you’ve seen this, but GitHub is capable of
rendering STL (think monochromatic triangles) on a web page. I am unsure
of integration with python, numpy, etc. I have written a small X3D JSON
to STL converter, see below link. But it’s JavaScript, so it would
require conversion to python for you!
https://github.com/coderextreme/X3DJSONLD/blob/master/src/main/node/convertJsonToStl.js
This would be especially helpful if you want to reduce the number of
Transforms in your scenegraph. I would like to include more types of
getting geometry, but I’m not energetic enough to do the triangularization
for all the X3D geometries. The code has been languishing for some time.
Note that my code produces higher than 3 vertex polygons, so it’s not true
STL.
Here’s an STL example on GitHub:
https://github.com/coderextreme/X3DJSONLD/blob/master/src/main/stl/example.stl
I would like to improve the SuperCobra.stl example.
So limited use case, but handy if you want to render graphics on GitHub!
“Safe” graphics!
On Wed, Feb 9, 2022 at 10:24 AM Hans Moritz Guenther <hgunther at mit.edu>
wrote:
> Hi,
>
> I'm starting to use the x3d.py library to generate x3d output. I'm very
> much a Python programmer using what people call the "scientific stack" in
> Python (the libraries numpy, scipy, pandas, etc.) with very little
> experience in 3D visualization or web-programming.
>
> I understand that you autogenerate the programming language API from the
> X3DOUM, but I do not know which, if any, of the comments generalize to the
> APIs in other programming languages or which ones are specific to the
> Python implementation in x3d.py.
>
> For a little bit of background, I'm an astronomer and one of the things I
> do is ray-tracing of the designs for new space-based observatories. It is
> then very useful to have some form of output that allows me to put images
> of how the instrument looks and what path the photons take into
> presentations or on the web. As it turns out, X3D is a great format for
> that, see e.g. https://space.mit.edu/home/guenther/ARCUS/3Dview.html
> <https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fspace.mit.edu%2Fhome%2Fguenther%2FARCUS%2F3Dview.html&data=04%7C01%7Cbrutzman%40nps.edu%7Cdb2b534b2a804d7bfdd208d9ea4aeafa%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C637798431440614306%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=%2FT7oRCpoMKrtbHjscVH9lQp%2FBP070YtGI6t4TF%2BPoL0%3D&reserved=0>
> In that past, I've generated the X3D output through a python package called
> mayavi (https://docs.enthought.com/mayavi/mayavi/
> <https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.enthought.com%2Fmayavi%2Fmayavi%2F&data=04%7C01%7Cbrutzman%40nps.edu%7Cdb2b534b2a804d7bfdd208d9ea4aeafa%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C637798431440614306%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=CdLWWXcET8e3si%2BUjGRjAkGfv2TvSQ9KKIlM9bc66oA%3D&reserved=0>)
> but that is a rather heavy dependency for this very limited purpose. So,
> I'm trying to convert to use your x3d.py library instead.
>
> First, let me thank you for your effort to make x3d.py at all. In general
> it works great!
>
> I'd like to mention a few glitches I've run into so far:
>
> - IndexTriangleSet: Coordinates are given as a list of tuples [(x1, y1,
> z1), (x2, y2, y3), ...]. I think that makes sense. It orders stuff in a
> natural way and is easy to understand. However, the index needs to be given
> as a flat list [ind11, ind12, ind13, ind21, ind22, ind23, ...]. Since there
> are three indices per triangle, I think the same list of tuples as for the
> coordinates would make more sense [( ind11, ind12, ind13), (ind21, ind22,
> ind23) ...]. I've not checked if the same thought applied to e.g. the
> IndexedFaceSet etc. I'm still pretty new to this and can't claim to know
> all relevant nodes.
>
> - the __init__.py file. The file is present, but not correct. It lists all
> the classes in __all__ but does not actually import them. Thus, that can't
> actually be used.
>
> In [1]: import x3d
>
> In [2]: x3d.IndexedTriangleSet
> ---------------------------------------------------------------------------
> AttributeError Traceback (most recent call last)
> <ipython-input-2-93a98d5f0414> in <module>
> ----> 1 x3d.IndexedTriangleSet
>
> Instead, I need to use "x3d.x3d". That's of course possible but a little
> cumbersome.
>
> In [4]: import x3d.x3d
> x3d.py package loaded, have fun with X3D Graphics!
>
> In [5]: x3d.x3d.IndexedTriangleSet
> Out[5]: x3d.x3d.IndexedTriangleSet
>
> I think all that's missing is the following line in the __init__.py
>
> from x3d import *
>
> which will import everything that's defined in x3d.py into the __init__.py
> namespace and than the user an get it from "import x3d" which gives you the
> names defined in x3d/__init__.py
> - Python usually makes heavy use of duck-typing (you can use any object as
> long as it behaves as you expect) instead of explicit "isinstance" checks.
> A lot of numerical computations in Python are done using the numpy (
> https://numpy.org
> <https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fnumpy.org%2F&data=04%7C01%7Cbrutzman%40nps.edu%7Cdb2b534b2a804d7bfdd208d9ea4aeafa%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C637798431440614306%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=DgLaPPURD5FLJTT9FnjaglzyPNA9oeH93qpXmJIcHvM%3D&reserved=0>)
> library, which implements array-based math and is optimized in C. Numpy has
> datatypes that are essentially similar to Python int but fail an isinstance
> check, and I can pass those in some, but not all places in x3d.py. Here is
> an example that fails:
>
>
>
> ~/mambaforge/envs/kitchensink/lib/python3.10/site-packages/x3d/x3d.py in __init__(self, ccw, colorPerVertex, index, normalPerVertex, solid, color, coord, fogCoord, normal, texCoord, attrib, DEF, USE, IS, metadata, class_, id_, style_)
>
> 48191 self.ccw = ccw
>
> 48192 self.colorPerVertex = colorPerVertex
>
> > 48193 self.index = index
>
> 48194 self.normalPerVertex = normalPerVertex
>
> 48195 self.solid = solid
>
>
>
> ~/mambaforge/envs/kitchensink/lib/python3.10/site-packages/x3d/x3d.py in index(self, index)
>
> 48230 if index is None:
>
> 48231 index = MFInt32.DEFAULT_VALUE()
>
> > 48232 assertValidMFInt32(index)
>
> 48233 assertNonNegative('index', index)
>
> 48234 self.__index = index
>
>
>
> ~/mambaforge/envs/kitchensink/lib/python3.10/site-packages/x3d/x3d.py in assertValidMFInt32(value)
>
> 2622 if not isinstance(each, int):
>
> 2623 # print(flush=True)
>
> -> 2624 raise X3DTypeError('MFInt32 list has contained value=' + str(each) + ' with type=' + str(type(each)) + ' which is not a valid int')
>
> 2625 if not isValidMFInt32(value):
>
> 2626 # print(flush=True)
>
>
>
> X3DTypeError: MFInt32 list has contained value=1 with type=<class 'numpy.int64'> which is not a valid int
>
>
>
>
>
> There is an easy workaround:
>
>
>
> x3d.IndexedTriangleSet(index = [int(x) for x in myindex]
>
>
>
> but it would be nice if IndexedTriangleSet accepted my numbers directly.
>
> There are several ways of doing that, but the easiest is probably to change line 2622 to:
>
>
>
> if not int(x) == x:
>
>
>
> That will work for any object that can be converted to an int, including
> numpy, python decimal, fraction, ..
>
> - Numpy: One might consider taking numpy arrays directly, i.e. instead of
>
> x3d.Coordinate(point=[(x1, y1, z1), (x2, y2, y3), ...])
>
> one could do
>
> x3d.Coordinate(point=arr)
>
> where arr is a (3, n) numpy array. Now, if done naively that would require
> numpy as a dependency to x3d.py and it's probably good to avoid that.
> However, there are ways to accept numpy arrays without requiring numpy.
> That's a little more involved, but can be done (for example using
> decorators or a separate module (x3d.numpy_interface) or separate package
> (x3d-numpy)). Not sure if it's worth the effort at this point - that
> depends on what your future plans for this package are and how fast this is
> developing.
>
> - Changelog. From the pypi entry and the docs on
> https://www.web3d.org/x3d/stylesheets/python/python.html it was not quite
> clear to me how stable the package is or where I would see changes listed,
> for example, if you do the change that I suggested above (accepting index
> values as tuples instead of a flat list) that would break the interface.
> Would you do that? Where would I find a list of changes from one version to
> another?
>
> - Jupyter notebook: The Jupyter notebook seems like an ideal tool for work
> with X3D in Python, since it is rendered on the web and can display any web
> output. Here is a simple addition of a `_repr_html_`method to the Scene
> class in the x3d.py that will render any valid scene with no additional
> effort to the screen. Sure, the header is a little simplistic, but it's
> just a quick way to look at what your are specifying. Since I did not want
> to edit x3d.py itself, I simply made a new class that inherits from the
> x3d.Scene, but it would obviously be even easier if this was part of x3d
> itself. See
> http://nbviewer.org/github/hamogu/x3d-experiements/blob/main/Scence_for_notebook.ipynb
> for an example and note how the X3D output at the bottom is not just a
> screenshot, but a live output that your can zoom and rotate with your
> mouse, even though the notebook is not running live, but instead you just
> see the rendered output of what I run some time in the past on my laptop.
> (I admit that this is a naive implementation and it might be useful to add
> a few <meta> or <WorldInfo> nodes. Also, maybe Scene is not the best node,
> or not the only node, where to define this functionality, but it seems to
> work well.)
> class Scene(x3d.Scene):
> js_source = 'https://www.x3dom.org/download/x3dom.js'
> css_source = 'https://www.x3dom.org/download/x3dom.css'
> dimension_px = (600, 400)
> def _repr_html_(self):
> return(f"""
> <html>
> <head>
> <meta http-equiv="X-UA-Compatible" content="IE=edge"/>
> <script type='text/javascript' src='{self.js_source}'> </script>
> <link rel='stylesheet' type='text/css' href='{self.css_source}'></link>
> </head>
> <body>
> <x3d width='{self.dimension_px[0]}px' height='{self.dimension_px[1]}px'>
> {self.XML()}
> </x3d>
> </body>
> </html>
> """)
>
>
> Please let me know if there is anything I can do to help with this awesome
> package, that really makes generating X3D from Python so much simpler
> already.
>
> Yours,
> Moritz
>
> --
> Hans Moritz Günther
> Massachusetts Institute of Technology
> Kavli Institute for Astrophysics and Space Research77 Massachusetts Avenue <https://www.google.com/maps/search/77+Massachusetts+Avenue?entry=gmail&source=g>
> NE83-569
> Cambridge, MA 02139hgunther at mit.eduhttps://space.mit.edu/home/guenther/
>
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>
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