Preview

Click on cubes to delete

Mouse Introduction

We can detect when the user clicks on the screen using the default os.pullEvent or os.pullEventRaw, which we typically do in an infinite loop in a separate coroutine. From these, we receive the mouse button and the coordinates of the pixel, which we can pass on to the ThreeDFrame:getObjectIndexTrace function to get information on the object that was clicked (and which polygon of its model). 
local ThreeDFrame = ... -- the frame defined at the start of your program
local objects = { ... } -- the list of objects defined earlier in your program

-- ...

while true do
  local event, key, x, y = os.pullEvent()

  -- check if the event was a click
  if event == "mouse_click" then
    -- pass the rendered objects with the coordinates of the clicked pixel
    local objectIndex, polyIndex = ThreeDFrame:getObjectIndexTrace(objects, x, y)
  end
end

Full example

We can use this to remove objects that are clicked on, for example. Standalone example program code: 
local Pine3D = require("Pine3D")

local ThreeDFrame = Pine3D.newFrame()
ThreeDFrame:setCamera(-1, 0, -1, 0, 45, -45)

local objects = {}

-- create a grid of boxes with the specified grid size
local size = 3
for x = 1, size do
  for y = 1, size do
    for z = 1, size do
      objects[#objects+1] = ThreeDFrame:newObject("models/box", x, y-size*2, z)
    end
  end
end

while true do
  -- render the scene
  ThreeDFrame:drawObjects(objects)
  ThreeDFrame:drawBuffer()

  -- wait for user input
  local event, key, x, y = os.pullEvent()

  -- check if the event was a click
  if event == "mouse_click" then
    -- pass the rendered objects with the coordinates of the clicked pixel
    local objectIndex, polyIndex = ThreeDFrame:getObjectIndexTrace(objects, x, y)
    if objectIndex then -- check if an object was clicked
	  -- remove the object from the list of rendered objects
      table.remove(objects, objectIndex)
    end
  end
end
In case of cube models, the polyIndex value can be used to determine which side of the cube was clicked in order to place objects on that side for example.