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Rune <run### [at] mobilixnet dk> wrote:
> "Christoph Hormann" wrote:
>> I understand the problem, but it only occurs, if you
>> already start below the surface, so i wonder how this
>> happens (since originally everything is above and
>> there should be no way to get below)
> Not exactly correct.
> The old algorithm worked like this:
> The particle motion is calculated using an OldLocation and a NewLocation for
> the particle. The collision detection algorithm traces a ray between these
> two points:
> \ V /
> \ / /
> \ / /
> `--o--?
> /
> V
> Then both the OldLocation and the NewLocation are rotated around the
> collision point:
> \ /
> \ /
> \ /
> <--`--o--?--<
> In order to avoid errors the ray is moved a tiny bit along the normal vector
> of the surface:
> \ /
> \ /
> <-\---o---/-<
> `-----?
> The new algorithm works the same way except that if the algorithm loop is
> run more than once, then for each loop the ray is traced not from the
> OldLocation but from the collision point from the loop before. That works
> fairly well, but not perfect.
> Perhaps one reason for the occasional errors could be that a ray
> accidentally hits exactly between two triangles of the heightfield?
Have you considered only rotating the bit of the ray that you haven't
already travelled?
> \ V /
> \ / /
> \ / /
> <--`--o--?
Like so? That would keep the ray above the surface, just use a shorter
ray.
> In order to avoid errors the ray is moved a tiny bit along the normal vector
> of the surface:
> \ /
> \ /
> <-\---o---/-<
> `-----?
This might cause errors with highly contorted surfaces consider:
V
//
---------/
---------o-
V just misses hitting the tip of the upper surface. If it is moved along
the normal, it could end up inside the upper surface. You might want to
move a short distance along the ray itself. This means that any movement of
o will remain outside the surface.
Geoff
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