[vtkusers] Is VTK applicable to a CAD like program?
Aaron Linnen
alinnen at globalkiosk.com
Mon Aug 25 18:06:40 EDT 2003
Thanks for the thoughts and pointers, David. I think actually deforming
would be ideal, but too much to shoot for on this go around.
I'm going away for a week and will ruminate on this and see what I can
come up with.
Aaron
David.Pont at ForestResearch.co.nz wrote:
>Hi Aaron,
> interesting problem, I am not sure vtk can do what you want, although I
>have never worked with textures... so take what follows with plenty of
>salt...
>If you just want to attach different textures to 3D models the answer is
>yes, although there will be a bit of effort to understand and correctly
>manipulate texture coordinates to get the desired placement. If you want to
>actually etch the surface of the models, ie deform the geometry, this may
>be possible if you can dive into the C++ code and cut and paste existing
>bits of functionality into a class to do it.
>
>-If you want to pursue this read up on textures and texture coordinates:
>point your browser at:
>http://public.kitware.com/VTK/doc/release/4.0/html/classes.html and search
>on the page for 'Texture'
>-It is up to you to segment the different parts of the model. Seperate
>pieces (polydata), each mapped to a seperate vtk Actor, each with its own
>texture (possibly blank) is probably the way to go.
>-I have a suspicion there may be a limit of 1 texture per actor in vtk, so
>1 actor per part would avoid this limit. Assign each part a texture, then
>let the user modify it...
>-to actually deform (etch) the model surfaces: vtkWarp* classes might do
>something useful, but I suspect you would have to make a new class that
>does exactly what they do but using texture as input... ie a new class
>'vtkWarpTexture'... start with vtlWarpScalar, find the bit where it gets a
>scalar and change it to get a scalar from a texture via a texture
>coordinate... However for your application this implies the model surface
>would need very high point density to reproduce an etched line... perhaps a
>class that creates sufficient new polygons to reproduce the new surface...
>(search the web for 'offset surfaces')...
>
> regards
> Dave Pont
>
>
>
>
>
> Aaron Linnen
> <alinnen at global To: vtkusers at vtk.org
> kiosk.com> cc:
> Sent by: Subject: [vtkusers] Is VTK applicable to a CAD like program?
> vtkusers-admin@
> vtk.org
>
>
> 20/08/2003
> 10:40
>
>
>
>
>
>
>I'm hoping to pick your brains about a software that I'm currently
>working on, for any ideas and for where VTK might fit in best.
>
>The program is a domain specific CAD like program for the design of
>etched stonework, mostly monuments. The program has a collection of
>elements (line drawings) that can be placed on the stone, as well as
>allowing text items to be created and edited.
>
>The program has been in use for a number of years and the current design
>simply lets you edit the main surfaces of the stone as a flat surface,
>then has a (hand written, and poorly at that) perspective view. The
>program currently doesn't hand more complicated stones (e.g. made out
>of several stones, or oddly shaped with curves)
>
>It was in looking to rewrite and improve the perspective view that I
>started looking into VTK. To make use of it, I would need to make
>actual 3d models for the various stones. Looking into this I had the
>idea that maybe VTK could help with the editing portion too.
>
>My rough idea was if I was making the the 3d models anyways, I should be
>able to get VTK to generate the shape of the various surfaces that I
>could use as textures for the 3d view. So the editing would be on the 2d
>texture maps for now and not need much training for the users.
>
>So I'm wondering if given a shape, say a stone vase with 2 flat sides
>front and back and 2 rounded sides, looking like this in a top down view:
> ___
>(___) (please excuse my feeble attempts at ASCII art!)
> a) can I tag the 3d model data so that I know which polygons compose
>each of the 4 sides? What file format handles this nicely?
> b) can I get the texture shape needed for each of the sides (which may
>be composed of several polygons)
> c) would there be a way to handle pictures that wrap one 2 (or more)
>of the sides?
> d) what if this vase had a top that can also be engraved? Now a) needs
>to be able to mark 5 sides, c) potentially might need to wrap something
>on the front, top and right side for example.
> e) is there an accurate method of knowing where something is on the
>texture maps to on the 3d model? Say I needed to add a border exactly 1
>inch from the top of the vase?
>
>Well, as usual, writing it out has helped my already. If anyone has
>pointers or ideas on this it would be great. Particular parts of VTK
>that would apply would be appreciated too. Completely different methods
>are also welcomed :)
>
>If this is deemed too of topic for this list, I apologize and people can
>follow up off-list if that's more appropriate.
>
>Thanks,
>Aaron
>
>
>
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