buldthensnip/pkg/iceball/lib/phys.lua

--[[
Copyright (c) 2014 Team Sparkle

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-- No physics. Pass through map.
function phys_map_none()
	return {
		collides_with_map = function () return false end,
		move_by = function (obj, offset, delta) return delta end,
	}
end

-- Point.
function phys_map_point(settings)
	local this = {
		ref = mul_vv(settings.ref or vec(), vec(1,1,1,0)),
	}

	function this.collides_with_map(offset)
		-- Get the offset we want.
		offset = offset or vec()
		local v = add_vv(add_vv(obj.pos_get(), this.ref), offset)

		-- Now just look it up!
		return map_solid_get(devec3(floorv(v)))
	end

	function this.move_by(obj, offset, delta)
		-- Let's get some useful vectors.
		offset = offset or vec()
		local from = add_vv(offset, obj.pos_get())
		local cell = floorv(from)
		local dir = signhardv(delta)

		-- TODO!
		return delta
	end

	return this
end

-- Axis-aligned box.
function phys_map_abox(settings)
	local this = {
		v1 = mul_vv(settings.v1 or vec(), vec(1,1,1,0)),
		v2 = mul_vv(settings.v2 or vec(), vec(1,1,1,0)),
	}

	function this.collides_with_map(obj, offset)
		-- Get two offsets, and floor them both.
		offset = offset or vec()
		offset = add_vv(offset, obj.pos_get())
		local v1 = floorv(add_vv(this.v1, offset))
		local v2 = floorv(add_vv(this.v2, offset))

		-- Loop away!
		local x,y,z
		for z=v1.z,v2.z do
		for x=v1.x,v2.x do
		for y=v1.y,v2.y do
			if map_solid_get(x,y,z) then
				return true
			end
		end end end
		
		return false
	end

	function this.move_by(obj, offset, delta)
		-- Let's get some useful vectors.
		offset = offset or vec()
		local from = add_vv(offset, obj.pos_get())
		local size = sub_vv(this.v2, this.v1)
		local dir = signhardv(delta)

		-- Corner point.
		local corner = blendv(function (c) return c < 0 end, dir, this.v1, this.v2)
		local point = add_vv(from, corner)
		local cell = floorv(point)
		local bound1 = sub_vv(this.v1, corner)
		local bound2 = sub_vv(this.v2, corner)

		-- Distance to coordinate boundary.
		local ndist = sub_vv(point, cell)
		local pdist = sub_vv(vec(1,1,1), ndist)
		local dist = blendv(function (c) return c < 0 end, dir, ndist, pdist)

		-- Some other things.
		local chcounts = absv(sub_vv(floorv(add_vv(point, delta)), cell))
		local chcmax = dot3(chcounts, vec(1,1,1))
		local can_move = vec(1,1,1,0)
		local vel = absv(norm3(delta))
		vel = mapv(function (c) return ((c < -EPSILON or c > EPSILON) and c)
			or ((c < 0 and -EPSILON) or EPSILON) end, vel)

		-- Here's a useful function.
		-- TODO: Make this do a 2D slice, rather than the whole 3D box.
		-- TODO: Use a "get floor/ceiling" function instead of a "get this voxel" function.
		local function block_me(v1, v2)
			local x,y,z
			for z=v1.z,v2.z do
			for x=v1.x,v2.x do
			for y=v1.y,v2.y do
				if map_solid_get(x,y,z) then
					return true
				end
			end end end

			return false
		end

		-- Some more setup.
		local missed = vec()
		local timeleft = len3(delta)

		-- Move to cells.
		local i
		for i=1,chcmax do
			-- Find the first coordinate we will hit.
			local det = div_vv(dist, vel)
			local cmp

			if det.x < det.y and det.x < det.z then cmp = "x"
			elseif det.y < det.z then cmp = "y"
			else cmp = "z" end

			-- Move that distance along.
			local movement = mul_cv(det[cmp], vel)
			point = add_vv(point, mul_vv(mul_vv(can_move, dir), movement))
			dist = sub_vv(dist, movement)
			timeleft = timeleft - det[cmp]

			local displ = 0.001
			local cbounds = mapvv(function (d, c)
				return c + ((d < 0 and displ) or (1-displ)) end, dir, cell)
			point = blendv(function(c) return c ~= 0 end, can_move, point, cbounds)

			-- Now collide!
			local ctest1 = floorv(add_vv(point, bound1))
			local ctest2 = floorv(add_vv(point, bound2))
			ctest1[cmp] = cell[cmp] + dir[cmp]
			ctest2[cmp] = cell[cmp] + dir[cmp]
			can_move[cmp] = (block_me(ctest1, ctest2) and 0) or 1
			cell[cmp] = cell[cmp] + dir[cmp] * can_move[cmp]
			dist[cmp] = dist[cmp] + 1
		end

		-- Final movement
		local movement = mul_cv(timeleft, vel)
		point = add_vv(point, mul_vv(mul_vv(can_move, dir), movement))

		-- Check to see if our point is in the correct cell
		-- -1 -> displ
		--  1 -> 1-displ
		local displ = 0.001
		local cbounds = mapvv(function (d, c)
			return c + ((d < 0 and displ) or (1-displ)) end, dir, cell)
		--local pcell = floorv(point)
		--point = blendv(function(c) return c == 0 end, sub_vv(pcell, cell), point, cbounds)
		point = blendv(function(c) return c ~= 0 end, can_move, point, cbounds)

		-- Return our point
		--return sub_vv(delta, missed)
		return sub_vv(sub_vv(point, corner), from)
	end

	return this
end