Subject:
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Math Help Needed PLEASE
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Newsgroups:
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lugnet.cad.dev
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Date:
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Mon, 19 Jun 2000 07:32:49 GMT
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Viewed:
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570 times
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Hy,
I'm running into math problems again, after I recogniced whats the problem
with the movements in MLCad. Now here is what I would like to do:
There is a virtual grid which is bound to a part. The distance of the grid
lines is given by a vector 'GRID' [x-spacing, y-spaceing, z-spacing] (e.g.
default for coarse grid [10, 8, 10]. This grid rotates together with the part
so a rotation-matrix 'RM' is available. I assume the origin of the grid to be
the same as the origin of the part and the offset is a vector 'OFF'.
Now the user views the part (and invisible) the virtual grid seen from a
certain side given by the view-rotation-matrix 'VM'. If this matrix is [1,0,0
0,1,0 0,0,1] the part and grid is show from FRONT.
The user can move the move the part in x and y direction (which actual axes
depend on the view-rotation-matrix). I need to know where is the nearest point
on the grid for a given screen point 'PS' [x, y, z] (translated into model
space already)
I sum. everything now:
Given is a vector 'GRID', a rotation matrix 'RM' (for part and grid), a view-
rotation-matrix 'VM' and a screen point 'PS'.
Searched the snapped screen point 'SPS' which is snapped to the nearest grid
point.
Please help me with that!!!!
Thanks in advance,
Michael
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Message has 2 Replies:
 | | Re: Math Help Needed PLEASE
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| (...) What do you mean by "translated into model space" ? Back from World coordinates? By applying inv(VM)? How can you find a z value for the screen point. There are many possible values. (How do you go from 2D to 3D?) Assuming that you could find (...) (24 years ago, 19-Jun-00, to lugnet.cad.dev)
| | | Re: Math Help Needed PLEASE
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| (...) Transform PS from model space to unrotated part space. Round the x, y, z values to the nearest grid points. (add half a grid size, divide by grid size, multiply by grid size) Transform PS back to model space. I think this algorithm may be (...) (24 years ago, 19-Jun-00, to lugnet.cad.dev)
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