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(...) After reading the text (Great work on part of the LSC), these are my comments. I think it would be helpful to mention the used matrix in line type 1 is row orientated (more clearly then 'standard matrix'). A paragraph about line type 1 (...) (17 years ago, 21-Aug-07, to lugnet.cad)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) Is this really what the LDRAW spec is stating? Because that would be contrary to the OpenGL spec, in which the standard ordering of matrices is column-major. So if you have a row like a b c d e f g h That would be interpreted in OpenGL as a e (...) (17 years ago, 21-Aug-07, to lugnet.cad)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) Umm, so what? LDraw is not, and should not, be dependent on OpenGL. Having worked with transformation matrix in both formats, I find the row-major format much easier to hand-edit than column-major organization. At least for LDraw-type usage (...) (17 years ago, 21-Aug-07, to lugnet.cad)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) 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. Rob (17 years ago, 21-Aug-07, to lugnet.cad)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) 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 (...) (17 years ago, 21-Aug-07, to lugnet.cad)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) 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 API doesn't care if you use column major or row major matrices, it just expects an array of 16 floats with (...) (17 years ago, 21-Aug-07, to lugnet.cad)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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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
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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
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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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(...) The OpenGL 2.1 specification: page 23 Vertex Arrays "Matrices are loaded into these slots in column major order." page 43 Matrices LoadMatrix takes a pointer to a 4 × 4 matrix stored in column-major order as 16 consecutive floating-point (...) (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
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(...) I think we'll just include two examples of how the data would go into a matrix in the two different directions and leave it at that. At this point, I think the best thing would be to add something like the following to the currently proposed (...) (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
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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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(...) So we may considered this fully, please give your reasons for this request. The file names always fall at the end of the line, so, "because it's easier to parse" has already been considered by the LSC and discarded many thanks William Howard (17 years ago, 22-Aug-07, to lugnet.cad)
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(...) That's true. However, unless I'm badly mistaken, in addition to the xyz1 being at the end, you also need the other parameters to be in the proper direction in order to get the results that the LDraw library wants. The following two matrices (...) (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
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(...) I thought I'd add a clarification to the above. A quick look at LDView's (URL) Change History> file will show that I only added support for spaces in submodel filenames in version 3.0. Furthermore, I listed it as an addition, not a bug fix, (...) (17 years ago, 22-Aug-07, to lugnet.cad, FTX)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) Those matrices would be wrong in both cases (assuming xyz is the translation), you probably swapped those with the next matrices. :) (...) The first one here is a column major and the second is a row major matrix, and you are right, they are (...) (17 years ago, 22-Aug-07, to lugnet.cad)
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(...) My issue with spaces is not with programs supporting them or not, it's that the elements inside a line are delimited by spaces, you have 1 <space> color <space> x <space> ... <part> but then when it comes to file names that rule is broken. I (...) (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
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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
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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
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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: OpenGL spec (was LDraw File Format spec)
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(...) 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 (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
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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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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) Ok, the whitespace debate has gone on long enough. It's been years now! Someone in the LSC needs to step up and really define what's an acceptable filename, whitespace and all. Personally I think since MLCad is established, popular, and pretty (...) (17 years ago, 23-Aug-07, to lugnet.cad, FTX)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) I replied on another message but they are taking almost an entire day to show up. My reason is simply consistency: spaces are used to separate fields, but when it comes to file names, spaces are part of the field. If we used commas to separate (...) (17 years ago, 23-Aug-07, to lugnet.cad)
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| | 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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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) Are you authenticating by replying to the "Message awaiting authentication" email? If so, see my thread in lugnet.admin.general (and lugnet.-off-topic.test) about the very long delay I experience when auth-ing via email. Doing it via the web (...) (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
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(...) Hi Rob, Not to be indelicate, but LDraw was around *before* OpenGL. That said, I think the document *must* explicitly show something like this: a b c d e f g h i Furthermore I think the document must explain x, y and z. If I remember correctly (...) (17 years ago, 28-Aug-07, to lugnet.cad)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) Let me restate the above.....because I think I'm wrong about the timeline. LDraw is a stand alone specification, so what OpenGL expects is not relevent. The LDraw specification must specify what its coordinate and matricies formats mean, (...) (17 years ago, 28-Aug-07, to lugnet.cad)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) Actually, SGI released OpenGL in 1992, and (according to ldraw.org) James released LDraw in 1995. So OpenGL predates LDraw by 3 years. (...) Good point. You are correct that -y is "up". I don't see that anywhere in the spec, and it's quite (...) (17 years ago, 28-Aug-07, to lugnet.cad)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) I agree, and believe that both my proposed "sample matrices" as well as Tim's "transformation equation" will go into the final spec. --Travis (17 years ago, 28-Aug-07, to lugnet.cad)
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(...) Travis, I have *had to add* support for blanks in LPub, because so many kids expect to be able to use them. Unfortunatly, kids won't read the spec, they will just do what comes naturally. I'm an old goat, so I'm personally not a fan of blanks (...) (17 years ago, 28-Aug-07, to lugnet.cad, FTX)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) Travis, I'm quite satisfied with your dual format explanation. It is simple and concise. Kevin (17 years ago, 28-Aug-07, to lugnet.cad)
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(...) Also important is the fact that LDraw's model world is in a right-handed coordinate system. The current draft doesn't mention this. Steve (17 years ago, 28-Aug-07, to lugnet.cad)
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| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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(...) Yes. That will go into the new "-y is up" section. I'm open to suggestions on the exact wording on this section, but I suspect that we can copy from the authors' guide document, which I believe already describes this. --Travis (17 years ago, 28-Aug-07, to lugnet.cad)
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(...) I wanted to thank the LSC for their hard work on this topic. Good job bringing it to fruition. Kevin (Charter Member of the LSC) (17 years ago, 29-Aug-07, to lugnet.cad)
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