> >>>>> "R" == Randy Stiles <[email protected]> writes:
> R> 1) The base coordinate system should be in the VRML standard, not
ad-hoc
> R> 2) +Z should be up from ground plane, NOT into the screen
> R> 3) X-Y should define the ground plane
> R> 4) Should use the right hand rule
> Have I overlooked something? I thought the VRML spec (maybe somtimes
> not clear enough) defines a right handed coordinate system with a
> horicontal x-z-plane (x to the right, z towards viewer) and the y axis
> pointing upwards. For example the fields of Cube (x=width, y=height,
> z=depth), top/bottom of Cylinder, and the default cameras, looking
> from (0, 0, 1) horicontally into the world make that clear.
This is a good point: the cube clearly is designed and named for the
viewer to be looking at the horizon. Also, the example, "Sample.wrl"
shows a "world" with the X-Z plane as the floor.
Also, 5,6 are important:
> 5) rotations should be additive, body centered, NOT about fixed axis set
> 6) +Y should be forward in body-centered coordinates (i.e. if you
I may have missed it the cube example, but if the X-Z plane is
implicit in the standard, through this cube example, it will lead to people
missing the point. Even if everyone is adamant that XZ is the horizon plane,
and that +X is 'forward' for objects, and Inventor implicitly does additive
body-centered rotations, it still should be an explicit listing in the VRML
standard.
Since this is a source of confusion and it is a matter of interpretation
I think it is worth clarifying in the 1.0 spec.
The question is how?
With an explicit set of coordinate properties, as above.
It seems most people would like to create worlds as they would lay out a
map - (X == latitude, Y == longitude, Z == elavation)
The default camera would then give the god's eye point of view.
The cube would be a little inconsistent.
The cube is consistent with Inventor, which VRML is based on.
But I feel life will be easier for everyone dealing with
terrain, etc if we were using XY for horizon plane, and not XZ.
What is the mind set? Are we walking around looking at the horizon
or looking down at a map? Either way, sanity is only a rotate away.
Yep, it can be handled with a rotate. But there has to be one explicit
definition from which everyone can start.
-Randy
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