GetElementMatrix

From Multi Theft Auto: Wiki
Revision as of 09:55, 10 March 2015 by Arezu (talk | contribs) (Why was this text changed? the regular getElementMatrix returns false for objects that are not streamed in.)

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.

[[{{{image}}}|link=]] Note: The matrix returned by this function is not setup correctly for some calculations unless the legacy argument is set to false.
[[{{{image}}}|link=]] 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

table getElementMatrix ( element theElement [, bool legacy = true ] )

OOP Syntax Help! I don't understand this!

Method: element:getMatrix(...)
Variable: .matrix
Counterpart: 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.

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)

This example creates some more matrix utility functions

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

This example function allows you to get the element matrix of an element that is not streamed in.

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

Changelog

Version Description
1.3.0-9.04186 Added legacy argument

See Also