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# collisions against plans oblique - advices

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Hi... I would like to know how do you do with collision against oblique plane. I use bounding boxes for my model''s collision, and usually they work fine. But with plans oblique, bounding boxes show them limits... especially when bounding box doesn''t bound perfectly my model I should use more BBoxes for each model? but this method could make the game slower... perhaps is better not use plans oblique? I didn''t see often plans oblique in commercial games.... Ps: my problem born in this case
____    \                    ____\
|X |     \                   |X | \
|XX|      \                  |XX|  \
----       \                 ----   \
BBox     plane               Noooo!! damn it

not in this case
____          /               ____   /
|X |         /                |X |  /
|XX|        /                 |XX| /
----       /                  ----/
BBox     plane                 OK!!!

X
XX is a model

____
|  |
|  |
---- is a BB

/
/
/
/     is a plane


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Bounding boxes and bounding spheres are used in most commercial games (although this seems to be changing). Doing exact collisions is quite computationally expensive.

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What you should do is what you're doing now. If it tests true for collision, then you can test for a bounding box on each of those little X's. If any of those test true, then (if you wanted this much precision) you could do some plane-polygon collision tests for the X's whose bounding boxes tested true for collision.

EDIT: By "what you should do", i mean "what i would do." I am in no way qualified to offer any advice on any topic on this board.

[edited by - falkone on July 6, 2003 2:46:48 PM]

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yes, to use a BB collision is a good work in my opinion.
but for collision versus indoor structure (for exemple a cave wall) or for big irregular outdoor structures (like a hill or a big rock) I would use an exact collision, because tesselate those structures with many BBox is too much long..

but I''ve many problems to do a good BBox Vs. Triangle collision..
to make a line-triangle collision or a point-triangle collision is easy... but change the point into BBox isn''t so easy..

byezzz

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