[HOpenGL] (not?) using preservingMatrix

[jamin1001]

My last post was eaten by this "Nabble Forums" web page!

...

Ah, you're right.  What didn't compile for me was this additional line after
the preservingMatrix call:
putStr $ "Result matrix: " ++ (show rs) ++ "\n"


Instead, I want to return that value to use outside the call.  This is what
I was after, I think:

rs2 <- preservingMatrix $ do
      loadIdentity
      -- do whatever you want with your your matrix
      rs <- get ((matrix $ Just $ Modelview 0)::StateVar(GLmatrix GLdouble))
      return (rs)
putStr $ "Result matrix: " ++ (show rs2) ++ "\n"

Now, as for question #2, are there any pre-made ways to transform a vector
with a matrix, or do I have to do it by hand (same goes for cross product!)
(see the post
http://groups.google.com/group/comp.graphics.api.opengl/browse_thread/thread/831ee85b6f97eb15/2de3e6d9c6a1a9e5)



jamin1001 wrote:
> 
> 
> 
> Sebastian Sylvan wrote:
>> 
>> On 1/5/07, jamin1001 <jamin1001 at yahoo.com> wrote:
>>>
>>> Right, I buy that.  But I don't see how the C line
>>>
>>> glGetFloatv (GL_MODELVIEW_MATRIX, your_matrix_result) ;
>>>
>>> can be done, since it writes a result into your_matrix_result, so I
>>> would
>>> need something like:
>>>
>>> preservingMatrix $ do
>>>     loadIdentity
>>>     -- do whatever you want with your your matrix
>>>     rs <- get ((matrix $ Just $ Modelview 0)::StateVar(GLmatrix
>>> GLdouble))
>> 
>> This does indeed compile for me. GHC 6.6.
>> 
>> -- 
>> Sebastian Sylvan
>> +46(0)736-818655
>> UIN: 44640862
>> _______________________________________________
>> HOpenGL mailing list
>> HOpenGL at haskell.org
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>> 
>> 
> 
> 

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