[vtkusers] Mipmaps, zooming ideas?

[David.Pont at ForestResearch.co.nz]

Hi Andrew,
   I too have a current interest in using Mipmaps in vtk and have taken a
quick look at some of the vtk code. On Render vtkOpenGLPolyDataMapper makes
OpenGL calls to set texture coordinates and vtkOpenGLActor calls
vtkTexture->Load which makes OpenGL calls to load the texture. vtkLODActor
supports multiple mappers and it uses the best (slowest) that meets the
'AllocatedRenderTime'.

So I am thinking vtkLODActor (or vtkOpenGLActor ?) could be modified to
support multiple textures:
  A. using vtkCollection to derive a vtkTextureCollection which the user
loads with textures, OR
  B. the mipmap set could be derived internally using vtk image resampling
functions?.
The modified vtk*Actor would  ensure the appropriate OpenGL calls are made
to load the set of textures, rather than a single one. It seems OpenGL will
take care of which resolution to use where and when, and can blend between
discrete resolutions so details do not flicker in and out of view.

I found the following set of intros to mipmaps from a quick google:
http://www.csc.calpoly.edu/~hitchner/CSC476.S2003/OpenGLTexture.html
http://www.flipcode.com/tutorials/tut_atmap.shtml
http://www.parallab.uib.no/SGI_bookshelves/SGI_Developer/books/OpenGL_PG/sgi_html/ch10.html#id14713
http://openglforums.com/tutorials/tutorial8.html
http://www.nullterminator.net/gltexture.html

Having read up a bit I am not convinced this is a good solution for my
problem so I will pause here, but let me know how you get on.

   regards
       Dave Pont


|---------+----------------------------->
|         |           Andrew Usher      |
|         |           <A.C.J.Usher at damtp|
|         |           .cam.ac.uk>       |
|         |           Sent by:          |
|         |           vtkusers-admin at vtk|
|         |           .org              |
|         |                             |
|         |                             |
|         |           23/10/2003 23:37  |
|         |                             |
|---------+----------------------------->
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  |       To:       vtkusers at vtk.org                                                                                               |
  |       cc:                                                                                                                      |
  |       Subject:  [vtkusers] Mipmaps, zooming ideas?                                                                             |
  >--------------------------------------------------------------------------------------------------------------------------------|




Hello,

I'm currently making a visualization app where I've got some large
cosmological datasets and I'd like to use texture maps initally to
represent the data, and then zoom in to successively higher resolution
texture maps until I get to the point where I can switch to polygons
representing the data that can be picked and analysed. I guess I'm asking
if it's possible to use mipmaps with VTK or whether I need to just use
OpenGL for this? If so, would it be possible to do this in conjunction
with VTK?

Has anyone tried this with VTK? I guess its similar to the demos you see
with graphics cards when you start in space and zoom in on earth.

Thanks,

Andrew

---------------------------------------------------
Andrew Usher
Email: a.c.j.usher at damtp.cam.ac.uk
---------------------------------------------------
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