AttachElementsOffsets
From Multi Theft Auto: Wiki
This article concerns the note left in attachElements.
Problem
The offset coordinates reflect the object space, not the world space. This means that you cannot simply visualize the attachment in the map editor and calculate the offsets between the 2 sets of world coordinates for "theElement" and "theAttachToObject".
For example, if "theAttachToElement" has XYZ rotations, then "theElement" will inherit these rotations. The specified rotation offsets will then be performed from these starting rotation points. Simply put, "theElement" will be rotated twice.
Solution
The following code shows how to use offsets calculated in the map editor with 'attachElements':
addEventHandler( "onResourceStart", resourceRoot, function() -- Postion and rotations from the map editor: local mainPos = { -756, 995, 14 } local mainRot = { 0, 0, 90 } -- Two rotations are zero. See note in attachRotationAdjusted local subPos = { -756, 999, 24 } local subRot = { 89, 0, 177 } -- One rotation is zero. See note in attachRotationAdjusted -- Create the objects mainObject = createObject ( 17050, mainPos[1], mainPos[2], mainPos[3], mainRot[1], mainRot[2], mainRot[3] ) subObject = createVehicle ( 519, subPos[1], subPos[2], subPos[3], subRot[1], subRot[2], subRot[3] ) -- Attach so they look like what they do in the map editor attachRotationAdjusted ( subObject, mainObject ) end ) function attachRotationAdjusted ( from, to ) -- Note: Objects being attached to ('to') should have at least two of their rotations set to zero -- Objects being attached ('from') should have at least one of their rotations set to zero -- Otherwise it will look all funny local frPosX, frPosY, frPosZ = getElementPosition( from ) local frRotX, frRotY, frRotZ = getElementRotation( from ) local toPosX, toPosY, toPosZ = getElementPosition( to ) local toRotX, toRotY, toRotZ = getElementRotation( to ) local offsetPosX = frPosX - toPosX local offsetPosY = frPosY - toPosY local offsetPosZ = frPosZ - toPosZ local offsetRotX = frRotX - toRotX local offsetRotY = frRotY - toRotY local offsetRotZ = frRotZ - toRotZ offsetPosX, offsetPosY, offsetPosZ = applyInverseRotation ( offsetPosX, offsetPosY, offsetPosZ, toRotX, toRotY, toRotZ ) attachElements( from, to, offsetPosX, offsetPosY, offsetPosZ, offsetRotX, offsetRotY, offsetRotZ ) end function applyInverseRotation ( x,y,z, rx,ry,rz ) -- Degress to radians local DEG2RAD = (math.pi * 2) / 360 rx = rx * DEG2RAD ry = ry * DEG2RAD rz = rz * DEG2RAD -- unrotate each axis local tempY = y y = math.cos ( rx ) * tempY + math.sin ( rx ) * z z = -math.sin ( rx ) * tempY + math.cos ( rx ) * z local tempX = x x = math.cos ( ry ) * tempX - math.sin ( ry ) * z z = math.sin ( ry ) * tempX + math.cos ( ry ) * z tempX = x x = math.cos ( rz ) * tempX + math.sin ( rz ) * y y = -math.sin ( rz ) * tempX + math.cos ( rz ) * y return x, y, z end