Example of 3rd person camera setup

main.lua

local cam = require'cam'  -- https://github.com/jmiskovic/lovr-cam

local player_pos = Vec3()
local player_vel = Vec3(0, 0, -0.01)


local 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())
  return view_pose:mul(view_proj:invert()):mul(clip_from_screen)
end


local function getRay(world_from_screen, distance)
  local NEAR_PLANE = 0.01
  distance = distance or 1e3
  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))
  return ray
end


local function mouseOnGround(ray)
  if ray.origin:distance(ray.target) < 1e-2 then
    return vec3(0, 0, 0)
  end
  local ray_direction = (ray.target - ray.origin):normalize()
  -- intersect the ray onto ground plane
  local plane_direction = vec3(0, 1, 0)
  local dot = ray_direction:dot(plane_direction)
  if dot == 0 then
    return vec3(0, 0, 0)
  end
  local ray_length = (-ray.origin):dot(plane_direction) / dot
  local hit_spot = ray.origin + ray_direction * ray_length
  return hit_spot
end


function lovr.draw(pass)
  pass:text('Hold right\nmouse button\nto move\ntoward it', -2, 0.05, 0,  0.5, -math.pi/2, 1,0,0)
  if lovr.system.isMouseDown(2) then
    local world_from_screen = getWorldFromScreen(pass)
    local ray = getRay(world_from_screen)
    local spot = mouseOnGround(ray)
    local dt = lovr.timer.getDelta()
    player_vel:add((spot - player_pos) * dt)
    player_pos:add(player_vel * dt)
    player_vel:mul(0.95)
  end

  pass:setColor(0x101010)
  pass:plane(0, 0, 0,  20, 20,  -math.pi/2, 1,0,0)
  pass:setColor(0x505050)
  pass:plane(0, 0.01, 0,  20, 20,  -math.pi/2, 1,0,0, 'line', 100, 100)
  pass:setColor(0xD0A010)
  pass:capsule(player_pos, player_pos + vec3(0, 0.4, 0), 0.3)
  local player_azimuth = math.atan2(player_vel.z, player_vel.x)
  pass:setColor(0x804000)
  pass:cone(player_pos, 0.4, 0.5,  -player_azimuth - math.pi/2, 0,1,0)
  cam.center:lerp(player_pos, 0.1)
  d_azimuth = player_azimuth - cam.azimuth + math.pi
  -- add sign to angle, so that it's faster way around to reach the player's azimuth
  d_azimuth = (d_azimuth + math.pi) % (2 * math.pi) - math.pi
  cam.nudge(d_azimuth * 0.005)
end

cam.integrate()