RE: Crosswalk MAX coordinate system

["Luc Bolduc" <lucb(at)Softimage.COM>]

Hello Wessam,

You actually found an old bug in our XSI exporter and even in the doc!

What should be exported by XSI as the coord system is this:

SI_CoordinateSystem { 
 1, // right handed
 0, 
 1, 
 0, // x = SI_RIGHT
 2, // y = SI_UP
 4, // z = SI_IN
}

The one exported by Max is OK:

SI_CoordinateSystem { 
 1, // right handed
 0, 
 1, 
 0, // x = SI_RIGHT
 5, // y = SI_OUT
 2, // z = SI_UP
}

So, as you can see, to transfer from the Max coordinate system to the
XSI one, you simply have to perform a global rotation of -90 deg in x to
the imported scene. In Crosswalk we do this by adding a root node to the
imported scene and by setting the X rotation of that node to -90 deg.

thanks for highlighting this issue!
LB 

-----Original Message-----
From: owner-3dgames(at)Softimage.COM [mailto:owner-3dgames(at)Softimage.COM]
On Behalf Of Wessam Bahnassi
Posted At: April 6, 2007 3:12 PM
Posted To: 3dgames
Conversation: Crosswalk MAX coordinate system
Subject: Crosswalk MAX coordinate system


dotXSI files coming out from the 3dsMAX Crosswalk exporter have the
following setup:

handRotation: 1 (SI_RIGHT_HANDED)
xAxis: 0 (SI_RIGHT)
yAxis: 5 (SI_OUT)
zAxis: 2 (SI_UP)

I don't really follow how this would be mapped to XSI's right-handed
coordinate system. Z and Y are flipped with each other. It's basically
telling me to take the Y value and replace it with Z, but keep the sign
unchanged (because it matches XSI's right-handed system).
Is this how I should interpret these values? Obviously the way above
produces a mesh that is flipped around the XY plane in XSI.

I can ofcourse detect the case specifically and adjust it as required,
but I thought the whole idea of having such a flexible template is to
allow for modular coordinate system conversions (as opposed to having a
template that
says: Using MAX coordinates, using XSI coordinates, or using blah's
coordinates).

Thanks,
Wessam Bahnassi
Microsoft DirectX MVP,
Programmer
Electronic Arts
--
'Talk is cheap because supply exceeds demand'


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