[vtkusers] Re: Mesa 5.0.2 not drawing

[Patrick Brockmann]

Hi  all,

Here is my experience on off-screen rendering using Mesa.

> I've been trying to get vtk4.2.2 to work with Mesa in order to enable 
> off-screen rendering.  I've found that code that will work just fine 
> with OpenGL draws an empty screen under Mesa.  Has anyone experienced 
> this problem.  To test the issue, i used the cylinder example from the 
> examples/rendering directory and simply replaced the renderwindow and 
> renderer with Mesa objects, see below.
>
> The original Cylinder code compiles and works perfectly.  With Mesa, 
> all i get is an empty RenderWindow.
>
> Has anyone seen this before?


Compile Mesa, then use the following options :
OPENGL_INCLUDE_DIR            /home/user1/Mesa-5.0.1/include
OPENGL_gl_LIBRARY                /home/user1/Mesa-5.0.1/lib/libGL.a
OPENGL_glu_LIBRARY              /home/user1/Mesa-5.0.1/lib/libGLU.a
OPENGL_xmesa_INCLUDE_DIR /home/user1/Mesa-5.0.1/include
OSMESA_INCLUDE_DIR            /home/user1/Mesa-5.0.1/include
OSMESA_LIBRARY                    /home/user1/Mesa-5.0.1/lib/libOSMesa.a
...
VTK_OPENGL_HAS_OSMESA          ON
...
VTK_USE_MANGLED_MESA             OFF 

You can also specify GL2PS options to be able to use the 
vtkGL2PSExporter class
GL2PS_INCLUDE_PATH         /home/user1/gl2ps
GL2PS_LIBRARY                    /home/user1/gl2ps/libgl2ps.so

After this, just add to your code renWin.OffScreenRenderingOn() to run in a
offscreen mode (Default OpenGL has not this feature available).
Here is the python code:
****************************************
#!/usr/bin/env python

from vtkpython import *

renWin=vtkRenderWindow()
renWin.OffScreenRenderingOn()

ren=vtkRenderer()
renWin.AddRenderer(ren)

cone=vtkConeSource()

mp=vtkPolyDataMapper()
mp.SetInput(cone.GetOutput())

actor=vtkActor()
actor.SetMapper(mp)

ren.AddActor(actor)

renWin.Render()

w2if=vtkWindowToImageFilter()
w2if.SetInput(renWin)

wr=vtkPNGWriter()
wr.SetInput(w2if.GetOutput())
wr.SetFileName("OffScreenCone.png")
wr.Write()

psw = vtkGL2PSExporter()
psw.SetInput(renWin)
psw.SetFileFormat(0)
psw.SetFilePrefix("OffScreenCone")
psw.Write()
****************************************

- Patrick

-- 

mailto:Patrick.Brockmann at cea.fr
01.69.08.72.23 --> LSCE (Orme des merisiers 701, Bureau 50)
01.44.27.21.10 --> IPSL (Jussieu, Tour 26, 4eme)
http://www.ipsl.jussieu.fr/~brocksce/