Re: [PyOpenGL-Users] Library choice for basic solid isometric rendering

[Mike C. F. <mcf...@vr...>]

Darren Hart wrote:
> I'm looking for a python library to use to do simple 3D-isometric
> renderings embedded in a gtk cabinet cad program. I'm looking to do
> "solid" renderings with all visible edges in black lines with all the
> visible faces a solid white - I don't want to see the occluded parts
> of the cabinet. (if there is a term to describe this, please educate
> me!). I'd like to be able to convert these to a readily printable
> format.
>   
A simple depth buffer will remove the hidden lines.  You can either do a
shader or a series of line segments/loops to render the edges you want
to display.  Normally those will be *just* those edges which the user
thinks of as edges (not the edge of every triangle), so it's likely
easiest just to draw the lines and have full control over them.  In
terms of printable formats, that depends on whether you want an
SVG/PDF/vector graphic or a simple bitmaps.  Everything will easily
produce bitmap images at screen (low) resolution, and many can render to
an off-screen buffer for higher-resolution images.  For a vector image
you can use gl2ps or the like, which attempts to hook the low-level GL
and capture the primitives into a buffer.  Failing that, math is your
friend (an likely a better approach for a CAD system if you're intending
to use the output as plans).
> I've looked at several libraries: python-opengl, python-gtkglext,
> python-visual, OSG, VTK, crystal-space, ogre, etc. I don't know enough
> yet to understand how much of an abstraction I need or which of all of
> these is the best starting point. Seeing as how python-opengl would be
> involved in most of these  I thought I'd ask here for advice on which
> of these to start trying to learn more about.
>   
Your query really needs to include how comfortable you are with
low-level programming and for what you want to optimize.  OSG is a huge
hammer, it should be able to handle anything you can throw at it, but
it's also a big 3D scenegraph library you'll need to wrap your head
around and package with your app.  PyOpenGL and GTKGLExt (which is just
an OpenGL visual really) are extremely low-level, if you're happy
slinging shaders and arrays-of-vertices, that might be appropriate. 
Crystal-space and Ogre are more focused on the needs of game developers,
but the engines are large collections of rendering processes nicely
packaged from what I hear.  VTK is more focused on visualization of
datasets, from what I hear.  Choosing one of the big packages means that
someone has likely done all the work for you.  Choosing one of the
low-level packages means you have to code it yourself, but it's just
going to do what you've told it to do.

HTH,
Mike

-- 
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com