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How I check if model's y aix is pointting up using maxscript? 
Hua*MuLan~ 
Actually , I have some idear,but I'd like to find some methods that are more convenient.
Every day is a new day MSN:qq343294964@hotmail.com
read 495 times 3/10/2009 10:45:10 AM (last edit: 3/10/2009 10:45:10 AM)

advancesoftware 
See : http://en.wikipedia.org/wiki/Dot_product
[Geometric interpretation section]
a = (0,1,0)  world space up vector. b = your model's up vector (normalized), in world space.
a.b = cos theta
theta = acos(a.b)
if theta is less than 90 degrees, the model's y axis is pointing up.
If you mean straight up, just grab the model's up vector in world space, normalize it & see if it's (0,1,0) ... theta will be zero in the above calculation.
I don't know maxscript, but that's the maths.
read 489 times 3/10/2009 10:57:23 AM (last edit: 3/10/2009 1:31:59 PM)

Hua*MuLan~ 
Actually , I have some trouble these days becanse someon want me to design a script to check if the scene "+Y = up ". I failed to unstanding what it really mean until now .So my opportunity to a firm work as T.A. also lost . It may mean that Y axis point straight up , I think.
Every day is a new day MSN:qq343294964@hotmail.com
read 466 times 3/10/2009 11:22:12 AM (last edit: 3/10/2009 11:22:12 AM)

Hua*MuLan~ 
I will have a try to see if I can design a script using the maths method which u give me .thanx
Every day is a new day MSN:qq343294964@hotmail.com
read 460 times 3/10/2009 11:29:56 AM (last edit: 3/10/2009 11:29:56 AM)

Hua*MuLan~ 
I 'd like to get the position of a vertex in the model's local space . And then transform it into world space .I think if the vertex's Y_axis value(A) in local space has the same sign (all + or all ) with the value(B) in world space , it should point up , and more if B = A + value of model's Y_axis . it should straight up . Am I right?
Every day is a new day MSN:qq343294964@hotmail.com
read 454 times 3/10/2009 11:48:18 AM (last edit: 3/10/2009 11:48:18 AM)

advancesoftware 
No. You need to consider direction vectors, not points.
Consider a triangle laying on the plane y=0 . All the points have ycoordinates of zero. You cannot deduce from the point data whether the model faces up or down. You need to consider the transformation matrices & extract out up vectors.
3D maths is a bit tricky. It takes a while to get your head around it, but its not so hard.
read 445 times 3/10/2009 12:10:16 PM (last edit: 3/10/2009 1:40:37 PM)


