Object paint with snap

tool PlaceObj prompt:"Left click to place the asset in the scene. Right click to place the asset in default position. Hold SHIFT to ignore surface orientation." numPoints:2
(
fn sortByHitDistance n1 n2 = if n1[2] < n2[2] then -1 else if n1[2] > n2[2] then 1 else 0 
 
local theAssets, gR
!REG3XP1!>local _qsort = qsort
local _translate = translate
local _matFromNorm = matrixFromNormal
local _iRay = intersectRay
local hitNodes
 
on start do
(	
setWaitCursor()
theAssets = (selection as array)
hitNodes = for o in (geometry as array) where not o.isSelected and not o.isHiddenInVpt and not o.boxMode and o.renderable collect 
(	
local snap = snapshot o
snap.wirecolor = o.wirecolor
snap	
)
gR = point pos:[selection.center.x,selection.center.y,selection.min.z] cross:off
for o in theAssets where o.parent==undefined do o.parent=gR
setArrowCursor()
)
 
on freeMove do
(
local theRay = mapScreenToWorldRay viewPoint
local hit_results = for o in hitNodes collect 
(
local n = _iRay o theRay
if n!=undefined then #(n, distance theRay.pos n.pos) else dontCollect
)	
if hit_results.count>0 then 
(
_qsort hit_results sortByHitDistance
if shiftKey then gr.transform = _translate (matrix3 1) hit_results[1][1].pos
else gr.transform = _translate (_matFromNorm hit_results[1][1].dir) hit_results[1][1].pos
)	
else gr.transform = _translate (matrix3 1) worldPoint
)
 
on mouseAbort arg do gR.transform = (matrix3 1)
 
on stop do
(
with undo off (delete gR)
with undo off delete hitNodes
select theAssets
)
)

startTool  PlaceObj