 | | LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
Like all previous LSCs, the 2006/7 LSC was charged with ratifying the LDraw File Format 1.0 specification. After much work checking, and ratifying as necessary, all linked specs and language extensions, and many months of dicussions about the actual (...) (17 years ago, 20-Aug-07, to lugnet.cad) !
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) And if we hadn't been granted an extended term (to get the voting out of summer holidays), we probably wouldn't have gotten the job done either (not that we have yet, but there's every indication that we will). I wonder if that would have (...) (17 years ago, 20-Aug-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
William Howard schrieb: (...) "Every line of the file contains one command. With one exception, every command is independent of other lines. The exception is the BFC INVERTNEXT command which modifies the behaviour of the immediately following (...) (17 years ago, 20-Aug-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
William Howard schrieb: (...) "Write/Print" Please add a note that this is not allowed in official parts files on the PT. "File Type" In the way your wrote this artikel it is very confusing for newbees. It should be divided in two portions. Official (...) (17 years ago, 20-Aug-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) OK, I read the whole post and am reposting my comments here :-) Here are my comments. I'll delineate the section where appropriate. Purpose: "standard by which most create virtual LEGO® models" Due to past personal conflicts and missteps too (...) (17 years ago, 20-Aug-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) Hi there. I'm just getting up to speed with OpenGL so it will be a little while before I can really sink my teeth into this. But, one thing I have learned so far is that the rule about non-concave quads is actually a limitation of OpenGL. It (...) (17 years ago, 21-Aug-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) Actually I find it quite logically it's not supported. And I don't think it's a specific OpenGL thing. Once the vertices's are not concave, you basically stop having a Quad all to getter. It becomes a polygon, and how is the hardware supposed (...) (17 years ago, 21-Aug-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) I'm not sure yet what we on the LSC will decide with respect to concave quads. It may be that we'll change that paragraph to a recommendation. I personally don't like them, but I can see Orion's point. I may write a utility program to (...) (17 years ago, 21-Aug-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(I'll comment on other items later, but want to get this out ASAP.) (...) This is a question for both Orion and the LDraw part library admins. If I write a program that splits all the concave quads in all existing official parts into two triangles, (...) (17 years ago, 21-Aug-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) Keep in mind, the original LDraw tool treats concave quads as triangles, effectively ignoring the contained vertex. So, by the 0.27 "spec", concave quads are inappropriate. Which can be translated as they are disallowed, but the renderer copes (...) (17 years ago, 21-Aug-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) Page 16 of the OpenGL spec, v2.1 states: "Only convex polygons are guaranteed to be drawn correctly by the GL." Rob (17 years ago, 21-Aug-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) I'm new to this community, and am just learning 3D graphics, but I will comment on this as someone who will eventually use this file format to read in and render these parts in 3D. 1. Character encoding - for a file spec, not specifying this (...) (17 years ago, 21-Aug-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
--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)
|
| |
| | Re: OpenGL spec (was LDraw File Format spec)
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: OpenGL spec (was LDraw File Format spec)
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
(...) 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)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
|
|
The LSC would like to thank everyone for their comments on the draft specification so far. The three week period for comments will end Monday 10th September. William Howard On behalf of the 2006/7 LSC (17 years ago, 6-Sep-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - MATRIX section updated
|
|
(...) Based on comments made, I have updated the section of the spec related to part transformations. I'd appreciate it if the people involved in that discussion would take a look at the new text. Please note that there have been a number of other (...) (17 years ago, 10-Sep-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - MATRIX section updated
|
|
(...) I think it's fine although I do have one fairly minor nitpick. I'd rather the top and bottom of the large 'brackets' be done using / and \ as follows / a b c x \ | d e f y | | g h i z | \ 0 0 0 1 / to avoid confusion with determinates which (...) (17 years ago, 10-Sep-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - MATRIX section updated
|
|
(...) Works for me. --Travis (17 years ago, 11-Sep-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - MATRIX section updated
|
|
(...) Hey, could you perhaps toss in the word "homogeneous" when describing that matrix? I tend to find more complete explanations when I add that to my internet searches. Have fun, Don (17 years ago, 11-Sep-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - MATRIX section updated
|
|
(...) Before I do that, can someone tell me if a 3D transformation matrix that includes shear is still homogeneous? If not, then I'm not going to put it in. --Travis (17 years ago, 11-Sep-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - MATRIX section updated
|
|
(...) Yes, the matrix is still homogeneous. In fact this page contains a nifty explanation of how what we normally think of as a translation matrix is actually a shear matrix where the extra w dimension added to make things homogeneous is the fixed (...) (17 years ago, 11-Sep-07, to lugnet.cad)
|
| |
| | Re: LDraw File Format Spec 1.0 DRAFT - MATRIX section updated
|
|
(...) OK, I updated the first "4x4 3D transformation matrix" to now be "4x4 homogeneous transformation matrix". I didn't feel that leaving 3D in there somewhere was practical. Because of this, I intentionally left the text alone two sentences later, (...) (17 years ago, 11-Sep-07, to lugnet.cad)
|
