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Issue #25 (2): Collision detection sometimes hangs.

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Sometimes the expanding polytype algorithm takes a long time to
terminate, e.g. in situations like this:

 .-.
: +-:-+
 '-'  |
  |   |
  +---+

The issue here is that the EPA adds vertices very close to each other,
which makes the separation distance change very slowly. If this is the
case, consider the current separation distance as approximately correct
and continue.
This commit is contained in:
Matthias Richter 2013-08-13 15:34:58 +02:00
parent 0dc1e6c719
commit adfe9a9a5d
1 changed files with 4 additions and 1 deletions
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gjk.lua
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@ -65,14 +65,17 @@ local function EPA(shape_a, shape_b, simplex)
end end
-- the expanding polytype algorithm -- the expanding polytype algorithm
local last_diff_dist = math.huge
while true do while true do
local e = closest_edge(simplex) local e = closest_edge(simplex)
local px,py = support(shape_a, shape_b, e.nx, e.ny) local px,py = support(shape_a, shape_b, e.nx, e.ny)
local d = vector.dot(px,py, e.nx, e.ny) local d = vector.dot(px,py, e.nx, e.ny)
if d - e.dist < 1e-6 then local diff_dist = d - e.dist
if diff_dist < 1e-6 or last_diff_dist - diff_dist < 1e-10 then
return -d*e.nx, -d*e.ny return -d*e.nx, -d*e.ny
end end
last_diff_dist = diff_dist
-- simplex = {..., simplex[e.i-1], px, py, simplex[e.i] -- simplex = {..., simplex[e.i-1], px, py, simplex[e.i]
table.insert(simplex, e.i, py) table.insert(simplex, e.i, py)