Subject:
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Re: OpenGL spec (was LDraw File Format spec)
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Newsgroups:
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lugnet.cad
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Followup-To:
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lugnet.off-topic.debate
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Date:
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Thu, 23 Aug 2007 10:01:06 GMT
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Viewed:
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6234 times
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In lugnet.cad, Rob Ross wrote:
> In lugnet.cad, Leonardo Zide wrote:
> > In lugnet.cad, Travis Cobbs wrote:
> > > In lugnet.cad, Rob Ross wrote:
> > > > The "so-what" would be that I, as someone who will eventually read in these
> > > > files to create OpenGL renderings of them, would expect the matrices to be in
> > > > column-major order, unless explicitly stated otherwise.
> > >
> > > I think the original suggestion that we mention that it is in row-major format
> > > is valid. I agree that the fact that OpenGL (almost certainly one of the top
> > > two most used 3D APIs on the planet) uses column major format is a good reason
> > > to specify that LDraw uses row-major format, instead of just saying "standard".
> > > It just proves that "standard" in this context is ambiguous.
> > >
> > > --Travis
> >
> > You guys are both wrong, OpenGL is NOT column major. This is one of the
> > biggest mistakes I keep hearing people repeat about OpenGL.
>
> The OpenGL 2.1 specification:
>
> page 23
>
> Vertex Arrays
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> "Matrices are loaded into these slots in column major order."
>
> page 43
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> Matrices
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> LoadMatrix takes a pointer to a 4 × 4 matrix stored in column-major order as 16
> consecutive floating-point values, i.e. as
>
> a1 a5 a9 a13
> a2 a6 a10 a14
> a3 a7 a11 a15
> a4 a8 a12 a16
>
>
> (This differs from the standard row-major C ordering for matrix elements. If the
> standard ordering is used, all of the subsequent transformation equations are
> transposed,
> and the columns representing vectors become rows.)"
>
> page 264
>
> State and State Requests
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> If the uniform queried is a
> matrix, the values of the matrix are returned in column major order.
>
>
> Rob
As this thread is for the discussion of the LDraw specification can any further
debate of what the OpenGL specification may or may not say please be continued
on .off-topic.debate
Thanks
William
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Message has 1 Reply:
 | | Re: OpenGL spec (was LDraw File Format spec)
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| (...) Like I said before, the DOCS were written with column major notation but the API isn't column major. Please show me a place on the API where it requires a column major matrices, there isn't one. OpenGL matrices are simply an array of 16 (...) (17 years ago, 23-Aug-07, to lugnet.off-topic.debate)
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