Eleftherios Garyfallidis wrote:
> Hello,
>
> Thank you again for your response.
>
>  Show quoted text 
> On Tue, Apr 13, 2010 at 11:20 AM, Greg Ewing
> <greg.ewing@... <mailto:greg.ewing@...>> wrote:
>
> Eleftherios Garyfallidis wrote:
> > to get
>
> the near plane I believe you need to gluUnProject with z=0.
> and to get the far plane you need to gluUnProject with z=1
>
>
> You're quite right, I was misremembering, sorry.
>
>
> Surprisingly, when I do glu.gluUnProject(x,viewport[3]y,0.)
> and glu.gluUnProject(x,viewport[3]y,1.) in PyOpenGL it seems
> it works fine but when I am feeding the transformation
> matrices by myself I am getting this error "Projection Failed".
>
>
> That sounds like there is something wrong with your matrices.
> How are you getting them? Are you getting them directly from
> OpenGL, or calculating them yourself? If you're calculating them
> yourself, you might be making a mistake somewhere.
>
>
> What happens if you retrieve the relevant matrices from OpenGL
> and feed them to gluUnProject? If that works, compare them with
> your own matrices to see if there is a difference.
>
>
> Yes this is what I am doing just calculating these matrices using
> the following PyOpenGL functions
>
> import OpenGL.GL as gl
>
> modelviewmatrix=gl.glGetDoublev(gl.GL_MODELVIEW_MATRIX)
>
> projectionmatrix=gl.glGetDoublev(gl.GL_PROJECTION_MATRIX)
>
> viewport=gl.glGetDoublev(gl.GL_VIEWPORT)
I have not followed this thread at all  so I don't know the history.
Nevertheless, I see a potential problem.
The call to gluUnProject expects the viewport to be passed in as
integers (GLint*) so you should be using glGetIntegerv not glGetDoublev
to get the viewport as an array of integers.
Here's gluUnProject's spec:
GLint gluUnProject( GLdouble winX,
GLdouble winY,
GLdouble winZ,
const GLdouble * model,
const GLdouble * proj,
const GLint * view, // !!!!!
GLdouble* objX,
GLdouble* objY,
GLdouble* objZ);
Using glGetDoublev for the two matricies and glGetIntegerv for the
viewport as input to gluUnProject has always worked well for me.
>
> These matrices are numpy arrays do you think that it might be a
> problem when we put these as input in gluUnProject? Should I transform
> them into something else perhaps?
>
> By the way I do confirm that when using gluUnProject without feeding
> in the transformation matrices as in glu.gluUnProject(x,viewport[3]
> y,0.) does work correctly :) I made some tests with picking planes
> and the accuracy of picking was excellent!!! The tests involved
> checking if the segment AB (where A is near and B is far) intersects
> with planes. For my application I need to check against many planes so
> I made a function for this in cython. The link for the code is here
>
> http://github.com/Garyfallidis/Fos/blob/master/fos/core/collision.pyx
>
> Best wishes,
> Eleftherios
>
>
> 
>
> 
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Gary Herron, PhD.
Department of Computer Science
DigiPen Institute of Technology
(425) 8954418
