GetElementMatrix

2020-10-16T22:06:49Z

Daddy: /* Syntax */

{{Shared function}}
__NOTOC__
This function gets an [[element]]'s transform [[matrix]]. This contains 16 float values that multiplied to a point will give you the point transformed. It is most useful for matrix calculations such as calculating offsets. For further information, please refer to a tutorial of matrices in computer graphics programming.
{{Note|The [[matrix]] returned by this function is [http://bugs.mtasa.com/view.php?id{{=}}6984 not setup correctly for some calculations] unless the '''legacy''' argument is set to '''''false'''''.}}
{{Tip|''For [[matrix]] manipulation which goes beyond the basic examples given on this page, see the [[Lua matrix library]].'' If you are using MTA: SA 1.4 or higher, using the built-in [[matrix]] class is also recommended.}}
==Syntax==
<syntaxhighlight lang="lua">
table getElementMatrix ( element theElement [, bool legacy = true ] )
</syntaxhighlight>
{{OOP||[[element]]:getMatrix|matrix|setElementMatrix}}

===Required Arguments===
*'''theElement:''' The [[element]] which you wish to retrieve the [[matrix]] for.

===Optional Arguments===
*'''legacy:''' Set to ''false'' to return correctly setup [['''matrix''']] (i.e. Last column in the first 3 rows set to zero).

===Returns===
Returns a multi-dimensional array (which can be transformed into a proper [[matrix]] class using ''Matrix.create'' method) containing a 4x4 matrix. Returns ''false'' if the element is not streamed in, and not a [[vehicle]], [[ped]] or [[object]].

==Example==
This example creates a utility function that turns an offset into a position that is relative to the specified element.
<syntaxhighlight lang="lua">
function getPositionFromElementOffset(element,offX,offY,offZ)
local m = getElementMatrix ( element ) -- Get the matrix
local x = offX * m[1][1] + offY * m[2][1] + offZ * m[3][1] + m[4][1] -- Apply transform
local y = offX * m[1][2] + offY * m[2][2] + offZ * m[3][2] + m[4][2]
local z = offX * m[1][3] + offY * m[2][3] + offZ * m[3][3] + m[4][3]
return x, y, z -- Return the transformed point
end

-- Get the position of a point 3 units to the right of the element:
x,y,z = getPositionFromElementOffset(element,3,0,0)

-- Get the position of a point 2 units in front of the element:
x,y,z = getPositionFromElementOffset(element,0,2,0)

-- Get the position of a point 1 unit above the element:
x,y,z = getPositionFromElementOffset(element,0,0,1)

</syntaxhighlight>

This example creates some more matrix utility functions
<syntaxhighlight lang="lua">
function getMatrixLeft(m)
return m[1][1], m[1][2], m[1][3]
end
function getMatrixForward(m)
return m[2][1], m[2][2], m[2][3]
end
function getMatrixUp(m)
return m[3][1], m[3][2], m[3][3]
end
function getMatrixPosition(m)
return m[4][1], m[4][2], m[4][3]
end

local mat = getElementMatrix(element) -- Get the matrix
x,y,z = getMatrixLeft(mat) -- Get the matrix left direction
x,y,z = getMatrixForward(mat) -- Get the matrix forward direction
x,y,z = getMatrixUp(mat) -- Get the matrix up direction

</syntaxhighlight>

This example function allows you to get the element matrix of an element that is not streamed in.
<syntaxhighlight lang="lua">
function getElementMatrix(element)
local rx, ry, rz = getElementRotation(element, "ZXY")
rx, ry, rz = math.rad(rx), math.rad(ry), math.rad(rz)
local matrix = {}
matrix[1] = {}
matrix[1][1] = math.cos(rz)*math.cos(ry) - math.sin(rz)*math.sin(rx)*math.sin(ry)
matrix[1][2] = math.cos(ry)*math.sin(rz) + math.cos(rz)*math.sin(rx)*math.sin(ry)
matrix[1][3] = -math.cos(rx)*math.sin(ry)
matrix[1][4] = 1

matrix[2] = {}
matrix[2][1] = -math.cos(rx)*math.sin(rz)
matrix[2][2] = math.cos(rz)*math.cos(rx)
matrix[2][3] = math.sin(rx)
matrix[2][4] = 1

matrix[3] = {}
matrix[3][1] = math.cos(rz)*math.sin(ry) + math.cos(ry)*math.sin(rz)*math.sin(rx)
matrix[3][2] = math.sin(rz)*math.sin(ry) - math.cos(rz)*math.cos(ry)*math.sin(rx)
matrix[3][3] = math.cos(rx)*math.cos(ry)
matrix[3][4] = 1

matrix[4] = {}
matrix[4][1], matrix[4][2], matrix[4][3] = getElementPosition(element)
matrix[4][4] = 1

return matrix
end
</syntaxhighlight>

<section name="Server side: Front to Front" class="server" show="true">
-- create a Ped (0, 0, 5, 0) and put the player to 10 m of distance, front to front
<syntaxhighlight lang="lua">
function startedThisResource (res)
if getThisResource() == res then
local thePed = createPed ( 287, 0, 0, 5, 0)
local matrix = getElementMatrix(thePed)
nx = 0 * matrix[1][1] + 10 * matrix[2][1] + 0 * matrix[3][1] + 1 * matrix[4][1]
ny = 0 * matrix[1][2] + 10 * matrix[2][2] + 0 * matrix[3][2] + 1 * matrix[4][2]
nz = 0 * matrix[1][3] + 10 * matrix[2][3] + 0 * matrix[3][3] + 1 * matrix[4][3]
for a, z in ipairs(getElementsByType("player")) do
setElementPosition (z, nx, ny, nz)
local playerX, playerY, playerZ = getElementPosition(z)
local pedX, pedY, pedZ = getElementPosition(thePed)
local rotZ = findRotation( playerX, playerY, pedX, pedY )
setElementRotation(z, 0, 0, rotZ)
end
end
end
addEventHandler("onResourceStart", getRootElement(), startedThisResource)

function findRotation( x1, y1, x2, y2 )
local t = -math.deg( math.atan2( x2 - x1, y2 - y1 ) )
return t < 0 and t + 360 or t
end
</syntaxhighlight>
</section>

==Changelog==
{{ChangelogHeader}}
{{ChangelogItem|1.3.0-9.04186|Added legacy argument}}

==See Also==
{{Client_element_functions}}

Multi Theft Auto: Wiki - User contributions [en]

GetElementMatrix