GetElementMatrix

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Revision as of 16:59, 27 August 2014 by Arezu (talk | contribs) (→‎Example)
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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.

Syntax

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

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 containing a 4x4 matrix. Returns false if the element is not streamed in, and not a vehicle or ped.

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 left 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 shows you what getElementMatrix does internally 

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



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