Recently , I was asked to design a script which used to check if scene is " +Y = up" without any farther explaination ? I just feel a little hard to undertand it . What will you think of it ? Is it offen used ?
It means you need to check if the coordinate system of something is Y up or Z up, I would assume. The question probably concerns Max (and CAD applications) which are Z up, while Maya and all other 3D apps I know of (as well as video and directX and openGL, etc.) are all Y up.
Y up or Z up ? These days I find that a models Y axis can’t Y up straightly . I indeed find some way (using dot product) to ensure that the model will Y up within certain theshold . You mean that?
In a mixed pipeline with assets coming from different applications (as Rob pointed out), you can’t really assume whether a model is Y or Z up. Y up vs. Z up is the orientation of the assets in the file. With a Y up orientation, a character would be facing the Z+ axis. With a Z up orientation, a character would be facing the +Y axis. For a visual representation of this look at this site - http://caad.arch.ethz.ch/info/maya/manual/UserGuide/Overview/ViewingScenes.fm.html
What it sounds like is that your script need to check the file to see which orientation is being used.
Yeah, sounds like a Maya-specific thing. You can change the world up axis in the Maya preferences - a script to do this automatically would be useful if you have a bunch of people who all need to be working in the same coordinate system (especially if it’s not the default).
Does Max have a way of changing which axis is “up”, or is it hard-coded?
[QUOTE=MoP;2672]Does Max have a way of changing which axis is “up”, or is it hard-coded?[/QUOTE]
:laugh:
did i miss something? o_O
Hehe… Z-up is hard coded in Max… it’s funny because if you have to ask a question like that in regards to Max the answer is almost always the thing you’d rather it not be. :D:
Over here we do assume that the scene is going to be z-up… even when exporting from Maya… Which really causes some problems with 3rd party scripts not working properly (because they assume y-up) or artists getting confused. Hopefully it will be addressed in the soonish. So yeah… best to make scripts that can work in either y/z instead of having to work around goofy issues like we are.
Don’t forget Normal maps!! To invert G or not !!! :D:
It’s seems more complex in Max as it involves something like float precision . Modus99 ! Agen Slot Modal Kecil Pasti Profit Pecah X500
I learned Max for several years and was really confident about myself in MXS . Things don’t like what I think of , in fact I just failed to be a real T.A. in a game company , for I mistook “+Y = up " as something we usually see in out loops like " ++i = 1” and designed a script which will move objects along Y axis . I just cann’t see these things all of your guys describled above via the simple description in the white paper saying “+Y = up” . I really asked the real meaning of “+Y = up” and what do they really want . But it’s seems they also want to check my abillity to understand these words , just keep it as secret from me . Does real T.A. often tackle problems that were wrotten on white papers with excessive ly simplified decription . I really want to be a T.A. . But tasks like these seems a little too hard for me new guys .
:(:
It’s not just Max, it’s a feature of floating-point maths. The Maya mel reference/ help files explicitly warn against comparing the result of any floating point operation to 0, for the same reason.
I think the task you were set is fair enough. Knowing that different apps use different coordinate systems and having a way of dealing it is pretty fundemental stuff, so it doesn’t surprise me that whoever wrote the question assumed that it was clear enough without further explanation. I certainly understood what it meant from your first post.
[QUOTE=Hua*MuLan~;2678]I really asked the real meaning of “+Y = up” and what do they really want . But it’s seems they also want to check my abillity to understand these words , just keep it as secret from me .
:(:[/QUOTE]
Like what Zen said, though I think the task was designed to show an undestanding of these fundamentals rather than solve the actual problem itself.
[QUOTE=Hua*MuLan~;2678]Does real T.A. often tackle problems that were wrotten on white papers with excessive ly simplified decription . I really want to be a T.A. . But tasks like these seems a little too hard for me new guys .
:(:[/QUOTE]
We do need to know this stuff and apply it day to day, for example, we have different projects on different coord systems (I know, don’t ask), and we need to transfer anim data across from time to time. And white papers are a fantastic resource for all sorts of stuff; interpretation and application of theories are very useful skills to have.
Use this as an opportunity, learn about coord systems (Zup, Yup are both the same really, give or take 90degs 
), but learn about right hand sets and left hand sets too, and the right/left hand rules for determining axis rotations etc, then take it further and learn the math behind this.
It’ll give you a solid understanding of the space you need to work in and stay you in good stead for the next interview.
Oh , i don’t come here for a couple of days . Thanx Zen? , actually , I rarely see mel reference , I will have a close look at it .Well , I should be responsilbe for the coordinator system . But I assume that if they should use +Y “pointing” up but not “=” up . What if “up” is a varible which actually holds a value?:D: . I post this tip just want to find out that if the “+Y = up” is widely used in MXS. They assume that I should finish the test in a whole day , and i just finished it in ten minmutes . The test paper prevent me from seeing the real problem of what it really is . Actually ,recently I do have some problems , for I must use the email to communitcates with my friends . Althought I love to do this job to design MXS , I have a deep anxiety that if I do not know the actually problems . Actually , I do not have much experence in game industry . I just learn max myself .
To be honest ， If that is science , all thoeries/formulas are thoeries/formulas , only if they are under certain context/conditions . If not , anything can happen . I do not kown how widely this description has been used . I insisted on my idear that do use “+Y = up” under certain context .
Oh , I just a learner . I just make mistakes every day in every aspects 
.
Perhaps , actually , I may still be going to make mistakes for a couple of years:P
I really expected the thread I rised is just limited as a discussion about technical problems .And pretty glad to have a hot discussion.
Based on this . See the following :
“The Maya mel reference/ help files explicitly warn against comparing the result of any floating point operation to 0, for the same reason.”
Models which begin in the top view in max , it’s up axis is the perfect world-up vector [0,0,1] . I have test it for more than once . No need to worried about the comparsion . Models begin in other viewports , do not have this advantage.
Any comments , disagreements , qustions , are still welcome and appreciated
Special thanx to Paul , for your patient . I was fightting my way to earn work experence ,pretty hard task