A GLScene rotation mesh builder class.
lazarus / 70-OpenGL

----------------------------------------------------------------------
dicepd · 2017-08-27 10:50

Designed to be subclassed or used as a helper class for parametric
mesh generation of rotated surfaces.

From the header (too lazy to type something like this again  )

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
GLRevolutionMeshObject;{   TGLRevolutionMeshObject     A class used to
build revolution onjects with features, such as shafts /    columms,
or with some work freeform.     Each section leaves an index value to
the last ring of Vertices made.    Callable routines should have the
option to use previous ring, mainly    for use with rounded features
where the normals are the same for both    edges of the feature.    
If previous ring is not used at a given Z then dup points will be   
generated, generally with a differing normal, which creates a hard
edge.    Hopefully this will create a topologically correct mesh, with
minimum    number of vertices.     Setting  FaceGroups[0]).Mode to
fgmmQuads will generate quad faces.    The default is triangular
faces.     Mesh density can be radially increased/decreased through  
MakeTransitionFiner and MakeTransitionCoarser. This is a stateful
change    which will keep the new density until another call is made. 
  NOTE: mesh density changing can only be used with triangular
meshes.     Revolutions should be built from the 'top' down. Top for
solid rotations    means highest point that meets the Z axis. See
Drilled hole example.    For shelled ojects such as a tube, top is the
lowest Z point and the inside    of the shelled rotation is generated
first.     Edges are stored with an index to the first ring and the
ring size.    This ring and the next ring should have congruent
vertices. But this will    allow only one ring to be used if we need
to collapse the edges for export,    reducing the risk of holes at the
edge vertices. Plus we can dispay them    for debugging :) where we
forget to set a UsePrevious to True.     TODO      Add in Tex coords
obviously only one is needed as the conic will      use either u or v
for the wrap round, and the other specified in the call      to build
the section? More thought required but basically not of interest     
for my immediate needs.       Optimisation Techniques Used.     Sine
and cosine calls removed from any inner loop by using predefined     
x,y 2D unit vectors.     Z components and normals are optimised by
taking into account the fact that      any affine vector rotated
around the Z axis will have the same z value.      So if we calculate
that once in 2D space on a major axis, the x.z plane      for
instance, the y component of the 2D unit vector becomes the z part   
 of the unit 3D vector and the x component becomes a scaling factor
to      use with the predefined xy unit vector array.     Added bonus
to the above approach is we are calculating unit vector    normals. No
need to call normalise on the Normals saving a sqrt call    per
vertex.                                      
How it is used can be seen from the example code in the test form.
Some comments on usage can be found in these code segement.

Enjoy

Peter

----------------------------------------------------------------------
BeanzMaster · 2017-08-27 11:02

Nice job can I'll include your sample in GLScene for the next update ?

----------------------------------------------------------------------
dicepd · 2017-08-27 11:14

Quote from: BeanzMaster on August 27, 2017, 01:02:45 pmNice job can
I'll include your sample in GLScene for the next update ?

Sure, no problem there.

Peter