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reworked intersect.lua - accepting that continuous collision is out of scope, reworking docs
This commit is contained in:
Max Cahill
parent
6ef19cfde0
commit
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162
intersect.lua
162
intersect.lua
@ -1,20 +1,22 @@
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--[[
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geometric intersection routines
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from simple point tests to shape vs shape tests
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optimised pretty well in most places.
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optimised pretty well in most places
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options for boolean or minimum separating vector results
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continuous sweeps (where provided) also return the
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time-domain position of first intersection
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TODO: refactor vector storage to be pooled where needed
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tests provided:
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overlap
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boolean "is overlapping"
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collide
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nil for no collision
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minimum separating vector on collision
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provided in the direction of the first object
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optional output parameters to avoid garbage generation
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]]
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local path = (...):gsub("intersect", "")
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local vec2 = require(path .. "vec2")
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local functional = require(path .. "functional")
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--module storage
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local intersect = {}
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@ -190,11 +192,6 @@ function intersect.line_line_collide(a_start, a_end, a_rad, b_start, b_end, b_ra
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intersected = "a"
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else
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intersected = "both"
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--collision point =
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--[[vec2:xy(
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a_start.x + mua * dx1,
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a_start.y + mua * dy1,
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)]]
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end
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end
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end
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@ -219,9 +216,14 @@ function intersect.line_line_collide(a_start, a_end, a_rad, b_start, b_end, b_ra
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table.insert(search_tab, {intersect._line_to_point(a_start, a_end, b_end), -1})
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end
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local best = functional.find_best(search_tab, function(v)
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return -(v[1]:length_squared())
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end)
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local best = nil
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local best_len = nil
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for _, v in ipairs(search_tab) do
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local len = v[1]:length_squared()
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if not best_len or len < best_len then
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best = v
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end
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end
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--fix direction
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into:vset(best[1]):smuli(best[2])
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@ -298,129 +300,6 @@ function intersect.aabb_aabb_collide(a_pos, a_hs, b_pos, b_hs, into)
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return res
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end
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--return normal and fraction of dt encountered on collision, false otherwise
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--TODO: re-pool storage here
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function intersect.aabb_aabb_collide_continuous(
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a_startpos, a_endpos, a_hs,
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b_startpos, b_endpos, b_hs,
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into
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)
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if not into then into = vec2:zero() end
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--compute delta motion
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local _self_delta_motion = a_endpos:vsub(a_startpos)
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local _other_delta_motion = b_endpos:vsub(b_startpos)
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--cheap "is this even possible" early-out
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do
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local _self_half_delta = _self_delta_motion:smul(0.5)
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local _self_bounds_pos = _self_half_delta:vadd(a_endpos)
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local _self_bounds_hs = _self_half_delta:vadd(a_hs)
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local _other_half_delta = _other_delta_motion:smul(0.5)
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local _other_bounds_pos = _other_half_delta:vadd(b_endpos)
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local _other_bounds_hs = _other_half_delta:vadd(b_hs)
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if not body._overlap_raw(
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_self_bounds_pos, _self_bounds_hs,
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_other_bounds_pos, _other_bounds_hs
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) then
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return false
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end
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end
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--get ccd minkowski box
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--this is a relative-space box
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local _relative_delta_motion = _self_delta_motion:vsub(_other_delta_motion)
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local _minkowski_halfsize = a_hs:vadd(b_hs)
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local _minkowski_pos = b_startpos:vsub(a_startpos)
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--if a line seg from our relative motion hits the minkowski box, we're in luck
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--slab raycast is speedy
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--alias
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local _rmx = _relative_delta_motion.x
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local _rmy = _relative_delta_motion.y
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local _inv_x = math.huge
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if _rmx ~= 0 then _inv_x = 1 / _rmx end
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local _inv_y = math.huge
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if _rmy ~= 0 then _inv_y = 1 / _rmy end
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local _minkowski_tl = _minkowski_pos:vsub(_minkowski_halfsize)
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local _minkowski_br = _minkowski_pos:vadd(_minkowski_halfsize)
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--clip x
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--get edge t along line
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local tx1 = (_minkowski_tl.x) * _inv_x
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local tx2 = (_minkowski_br.x) * _inv_x
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--clip to existing clip space
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local txmin = math.min(tx1, tx2)
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local txmax = math.max(tx1, tx2)
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--clip y
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--get edge t along line
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local ty1 = (_minkowski_tl.y) * _inv_y
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local ty2 = (_minkowski_br.y) * _inv_y
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--clip to existing clip space
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local tymin = math.min(ty1, ty2)
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local tymax = math.max(ty1, ty2)
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--clip space
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local tmin = math.max(0, txmin, tymin)
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local tmax = math.min(1, txmax, tymax)
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--still some unclipped? collision!
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if tmin <= tmax then
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--"was colliding at start"
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if tmin == 0 then
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--todo: maybe collide at old pos, not new pos
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local msv = self:collide(other, into)
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if msv then
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return msv, tmin
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else
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return false
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end
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end
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--delta before colliding
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local _self_collide_pre = _self_delta_motion:smul(tmin)
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--delta after colliding (to be discarded or projected or whatever)
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local _self_collide_post = _self_delta_motion:smul(1.0 - tmin)
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--get the collision normal
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--(whichever boundary crossed _last_ -> normal)
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local _self_collide_normal = vec2:zero()
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if txmin > tymin then
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_self_collide_normal.x = -math.sign(_self_delta_motion.x)
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else
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_self_collide_normal.y = -math.sign(_self_delta_motion.y)
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end
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--travelling away from normal?
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if _self_collide_normal:dot(_self_delta_motion) >= 0 then
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return false
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end
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--just "slide" projection for now
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_self_collide_post:vreji(_self_collide_normal)
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--combine
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local _final_delta = _self_collide_pre:vadd(_self_collide_post)
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--construct the target position
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local _target_pos = a_startpos:vadd(_final_delta)
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--return delta to target pos
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local msv = _target_pos:vsub(a_endpos)
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if math.abs(msv.x) > COLLIDE_EPS or math.abs(msv.y) > COLLIDE_EPS then
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into:vset(msv)
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return into, tmin
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end
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end
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return false
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end
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-- helper function to clamp point to aabb
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function intersect.aabb_point_clamp(pos, hs, v, into)
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local v_min = pos:pooled_copy():vsubi(hs)
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@ -449,7 +328,7 @@ function intersect.aabb_circle_collide(a_pos, a_hs, b_pos, b_rad, into)
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--
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local result
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if like_aabb then
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local pretend_hs = vec2:pooled():sset(b_rad)
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local pretend_hs = vec2:pooled():sset()
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result = intersect.aabb_aabb_collide(a_pos, a_hs, b_pos, pretend_hs, into)
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pretend_hs:release()
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else
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@ -553,8 +432,7 @@ function intersect.mutual_bounce(velocity_a, velocity_b, normal, conservation)
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velocity_a:fmai(b_remaining, conservation)
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velocity_b:fmai(a_remaining, conservation)
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--clean up
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a_remaining:release()
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b_remaining:release()
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vec2.release(a_remaining, b_remaining)
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end
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return intersect
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