mike@x.co.uk (Mike Moore) (06/26/91)
My armchair virtual world program has a problem....
I've picked up an object (a pyramid) and now I want to put it down so that
it rests on top of another object (a cube). I don't want point-of-view of
the user to change as the operation is done. The visual 3d feedback given
by the system can confuse the user as they have no idea of scale (i.e.
unless the user has actually walked up to each object and examined it,
s/he has no idea if the cube is large and far away or small and close by*).
I was thinking of using a shadow which appeared underneath the pyramid and
deformation of the shadow as it travelled over the cube would inform the
user of the pyramids position relative to the cube. This implies that the
light source generating the shadow must always be at a defined point,
preferably immediately above each object#.
Does anybody have any ideas about how to further progress this? Or good
books which discuss various methods of giving distance and relative
position feedback to the user?
Another point of interest in relation to perspective:
Infinity
/\<----/_e
/ \
/ a \
/~~~~~~\ -
/ \ |
/ \ |d
/ b \ |
/~~~~~~~~~~~~~~\ -
/ \ |c
/ \ -
Observer
o If an object has an actual width of 10 units then the apparent widths
a and b at distances c and d depend on the angle e. What is angle e?
Note: This is a genuine question, not an exercise.
o Do the same rules apply for the height of an object?
Mike Moore
* I know that I can get away from this problem by having some kind of
checker-board floor, but I don't *want* a checker-board floor!
# Something else I don't want.
--
Mike Moore | Sprechen Sie Deutsch? Ich moechte | The world is coming to an
IXI Limited | gerne eine(n) Elektroniker(in) als | end. Please log off.
mike@x.co.uk | Brieffreund(in) haben. | good@baviki.enet.dec.com (Michael Good) (06/27/91)
In article <1991Jun27.010103.10247@milton.u.washington.edu> Mike Moore <mike@x.co.uk> writes: >My armchair virtual world program has a problem.... > >I've picked up an object (a pyramid) and now I want to put it down so that >it rests on top of another object (a cube). I don't want point-of-view of >the user to change as the operation is done. The visual 3d feedback given >by the system can confuse the user as they have no idea of scale (i.e. >unless the user has actually walked up to each object and examined it, >s/he has no idea if the cube is large and far away or small and close by*). > >I was thinking of using a shadow which appeared underneath the pyramid and >deformation of the shadow as it travelled over the cube would inform the >user of the pyramids position relative to the cube. This implies that the >light source generating the shadow must always be at a defined point, >preferably immediately above each object#. > >Does anybody have any ideas about how to further progress this? Or good >books which discuss various methods of giving distance and relative >position feedback to the user? > >[Stuff deleted] > >* I know that I can get away from this problem by having some kind of >checker-board floor, but I don't *want* a checker-board floor! You may not want to use a checkerboard floor, but some type of textured ground (it can be more subtle than a checkerboard if your system has the graphics capability to display it quickly) is perhaps the most straightforward and ecological approach to solving this problem. Distance perceived along the ground is visible; distance perceived through space is not. See James Gibson's "The Ecological Approach to Visual Perception", pp. 117 and 160-164. Michael Good good@baviki.enet.dec.com