Example for dragging physics colliders with mouse in LÖVR

mouse_picking.lua

-- Creates a few hundred colliders which can be dragged around with right mouse button
-- Uses phywire.lua from https://github.com/jmiskovic/lovr-phywire

local phywire = require'phywire'

local world = lovr.physics.newWorld(0,0,0, false)
world:setLinearDamping(0.1)
world:setAngularDamping(0.1)

local mouse_collider = world:newSphereCollider(0,0,0, 0.001)
mouse_collider:setKinematic(true)
mouse_collider:getShapes()[1]:setSensor(true)

local is_orthographic = false
local world_from_screen = lovr.math.newMat4()

function getWorldFromScreen(pass)
  local w, h = pass:getDimensions()
  local clip_from_screen = mat4(-1, -1, 0):scale(2 / w, 2 / h, 1)
  local view_pose = mat4(pass:getViewPose(1))
  local view_proj = pass:getProjection(1, mat4())
  is_orthographic = view_proj[16] == 1
  return view_pose:mul(view_proj:invert()):mul(clip_from_screen)
end


local hovered = {}

local function randomQuaternion(q)
  q = q or quat()
  local u,v,w = math.random(), math.random(), math.random()
  -- from "Uniform random rotations" in Graphic Gems III by K. Shoemake
  q:set(math.sqrt(1-u)*math.sin(2*v*math.pi),
        math.sqrt(1-u)*math.cos(2*v*math.pi),
        math.sqrt(u)*math.sin(2*w*math.pi),
        math.sqrt(u)*math.cos(2*w*math.pi),
        true ) -- Raw components
  return q
end


for i=1,500 do
  local c = world:newBoxCollider(
    lovr.math.randomNormal(50, 0),
    lovr.math.randomNormal(50, 0),
    lovr.math.randomNormal(50, 0),
    2,
    2,
    2 + 3 * lovr.math.random())
  c:setOrientation(randomQuaternion())
  local c = world:newSphereCollider(
    lovr.math.randomNormal(50, 0),
    lovr.math.randomNormal(50, 0),
    lovr.math.randomNormal(50, 0),
    1,
    2 + 3 * lovr.math.random())
  c:setOrientation(randomQuaternion())
end


function getRay(distance)
  local NEAR_PLANE = 0.01
  distance = distance or 1e3
  local z
  local ray = {}
  local x, y = lovr.system.getMousePosition()
  ray.origin = vec3(world_from_screen:mul(x, y, NEAR_PLANE / NEAR_PLANE))
  ray.target = vec3(world_from_screen:mul(x, y, NEAR_PLANE / distance))
  if is_orthographic then
    -- this breaks othographic projections if camera is not looking down the -Z :(
    ray.origin.z = distance -- positive sign, so that ray crosses the XY plane
    ray.target.z = -1000
  end
  return ray
end


function lovr.update(dt)
  world:update(1/60)
  mouse_collider:setPose(lovr.headset.getPose('left'))
end


function lovr.draw(pass)
  world_from_screen:set(
    getWorldFromScreen(pass))
  phywire.draw(pass, world, phywire.render_shapes)
  local ray = getRay()
  world:raycast(ray.origin, ray.target,
    function(shape, x, y, z)
      local minx, maxx, miny, maxy, minz, maxz = shape:getAABB()
      local cx, wx = (minx + maxx) / 2,  maxx - minx
      local cy, wy = (miny + maxy) / 2,  maxy - miny
      local cz, wz = (minz + maxz) / 2,  maxz - minz
      pass:box(cx, cy, cz, wx, wy, wz, 0,  0,0,0, 'line')
      hovered.x, hovered.y, hovered.z = x, y, z
      hovered.collider = shape:getCollider()
    end)
end


function lovr.mousepressed(x, y, button)
  if button == 2 and hovered.collider then
    lovr.physics.newBallJoint(mouse_collider, hovered.collider, hovered.x, hovered.y, hovered.z)
  end
end


function lovr.mousereleased(x, y, button)
  for _, joint in ipairs(mouse_collider:getJoints()) do
    joint:destroy()
  end
  hovered = {}
end