 | | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments —Rob Ross
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| | | (...) I came across the *current* LDraw file spec here: (URL) the matrix example is using column-major ordering. So now I'm really confused. Does the current spec use column-major, and the new spec is proposing to change it? Or is the current spec (...) (17 years ago, 22-Aug-07, to lugnet.cad)
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| | | | | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments —Travis Cobbs
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| | | | (...) From the standpoint of OpenGL, it uses row-major ordering. There are two ways to draw a transformation matrix. OpenGL uses the following (array offsets shown after): A D G X 0 4 8 12 B E H Y 1 5 9 13 C F I Z 2 6 10 14 0 0 0 1 3 7 11 15 (...) (17 years ago, 22-Aug-07, to lugnet.cad)
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| | | | | | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments —Rob Ross
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| | | | (...) Hi again. What I meant was, I am confused by the (apparent) difference in what the *current* spec says on this issue, and what the new proposed spec says. If you will look at the current spec and scroll down near the end to the Line Format (...) (17 years ago, 22-Aug-07, to lugnet.cad)
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| | | | | | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments —Travis Cobbs
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| | | | (...) Yes, but look where the x, y, and z are. The example matrix is transposed vs the "standard" one shown in OpenGL text. If you swap the rows and columns in the above matrix, you'll get the OpenGL one. It's an alternate way of expressing a 3D (...) (17 years ago, 22-Aug-07, to lugnet.cad)
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| | | | | | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments —Timothy Gould
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| | | | (...) I think a full worked through example would do the specs a lot of good. If I understand right the line 1 c x y z a b c d e f g h i part.dat transforms any point by the operation (u, v, w)->(x+a*u+b*v+c*w, y+d*u+e*v+f*w, z+g*u+h*v+i*w) With it (...) (17 years ago, 22-Aug-07, to lugnet.cad)
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| | | | | | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments —Rob Ross
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| | | | (...) If I were new to 3D graphics (and I am ) I would be confused by this, I would have to ask someone else how to interpret the spec. I think Travis' proposal to show the two different matrices that can be built from the line of values is more (...) (17 years ago, 23-Aug-07, to lugnet.cad)
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| | | | | | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments —Timothy Gould
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| | | | --snip-- (...) I'm not new to matrices and Travis' example is still a little unrigorous which is why I propose the mathematically sound form above. Note the amount of discussion already here because of what people consider 'standard' or 'given' (...) (17 years ago, 23-Aug-07, to lugnet.cad)
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| | | | | | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments —William Howard
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| | | | (...) I think we need to draw this particular discussion to a close. From all the comments around matrix manipulation it is clear that this part of the specification is ambiguous and so needs further consideration. Unfortunately, whatever method we (...) (17 years ago, 23-Aug-07, to lugnet.cad)
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