Re: [PyOpenGL-Users] PyOpenGL Deprecation & New Methods

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

Prashant Saxena wrote:
> Hi,
>
> Are there any docs, article available for the deprecated function equivalent in 3.x api. Converting old school code completely
> using new api would be difficult with out good docs and references.
>
> For example
>
>             glEnableClientState(GL_COLOR_ARRAY)
>             glEnableClientState(GL_VERTEX_ARRAY)
>             
>             glColorPointer(4, GL_FLOAT, 0, self.colors)
>             glVertexPointer(2, GL_FLOAT, 0, self.vertices)
>
>             glPushMatrix()
>             glTranslatef(self.x, self.y, 0) #
>             glDrawArrays(GL_QUADS, 0, 4)
>             glPopMatrix()
>             
>             # Disable vertex arrays
>             glDisableClientState(GL_VERTEX_ARRAY) 
>             glDisableClientState(GL_COLOR_ARRAY)
>
> This is new way to draw quads using array method but glPushMatrix, glPopMatrix, glTranslate & glColor has been deprecated.
>   
Actually, that's the pretty-old-but-not-quite-the-oldest way to draw
quads (it's from OpenGL 1.1, January 1997), which is about 1/2 of the
way to legacy free.  To go legacy-free you then convert the code to use
shader attributes instead of the hard-coded color, vertex,
texture-coordinate etc. arrays (that's a trivial textual change) and
write shaders to render *all* of the quads with a single call (that's a
bit of work if you don't know GLSL yet).  Oh, and quads are
deprecated... you render two triangles...

Matrix operations are deprecated in their entirety, with only
shader-uniform matrices being available, i.e. you define a uniform
called "mv_matrix", another called "norm_matrix" and calculate the
matrices, passing them fully-formed to the shader alongside your data
for each object.  Point form description of what needs to happen is on
the deprecations page[1].

At this point I'd say "move to using arrays (and VBOs), investigate
shaders" is the best path to take, rather than trying to go fully
legacy-free all in one go.  Legacy-free operation has a higher barrier
to entry than the original OpenGL API, and when you go legacy free you
either have to provide fallback code for older hardware or just give up
on the less featureful hardware (e.g. my 2-year-old laptop with a crappy
Intel Integrated Graphics chip doesn't support GLSL at all).  I'm trying
to write a series of introductory tutorials[2] for legacy-free
operation, but I'm short on time (perennially), so you might not want to
hold your breath on it.

HTH,
Mike

[1] http://pyopengl.sourceforge.net/documentation/deprecations.html
[2] http://pyopengl.sourceforge.net/context/tutorials/index.xhtml

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