Difference between revisions of "BezierCurve:evaluate"

(→‎Make a circle follow a curve)
(→‎Examples: The new example tries to do the same thing as the evaluate() function (i.e. it's useless). It also produces the wrong result.)
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<source lang="lua">
 
<source lang="lua">
 
local controlPoints = {125,125, 125,225, 175,125, 225,125}
 
local controlPoints = {125,125, 125,225, 175,125, 225,125}
−
local curve = love.math.newBezierCurve(controlPoints)
+
local curve         = love.math.newBezierCurve(controlPoints)
  
 
function love.draw()
 
function love.draw()
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love.graphics.line(curve:render())
 
love.graphics.line(curve:render())
 
end
 
end
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</source>
 
−
 
−
 
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=== Calculate point at value t ===
 
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<source lang="lua">
 
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function evaluateBezier (controlPoints, t)
 
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local nPts = #controlPoints /2
 
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local Vtemp = {}
 
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for i = 1,  #controlPoints, 2 do
 
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table.insert (Vtemp, {x=controlPoints[i], y=controlPoints[i+1]})
 
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end
 
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for i = 2, nPts do
 
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for j = 1, i-1 do
 
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Vtemp[j].x = (1-t)*Vtemp[j].x + t*Vtemp[j+1].x
 
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Vtemp[j].y = (1-t)*Vtemp[j].y + t*Vtemp[j+1].y
 
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end
 
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end
 
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local Q = {x=Vtemp[1].x, y=Vtemp[1].y}
 
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return Q
 
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end
 
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local controlPoints = {125,125, 125,225, 175,125, 225,125}
 
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local t = 0.5
 
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local point = evaluateBezier (controlPoints, t)
 
 
</source>
 
</source>
  

Revision as of 20:25, 16 December 2021

Available since LÖVE 0.9.0
This function is not supported in earlier versions.

Evaluate Bézier curve at parameter t. The parameter must be between 0 and 1 (inclusive).

This function can be used to move objects along paths or tween parameters. However it should not be used to render the curve, see BezierCurve:render for that purpose.

Function

Synopsis

x,y = BezierCurve:evaluate(t)

Arguments

number t
Where to evaluate the curve.

Returns

number x
x coordinate of the curve at parameter t.
number y
y coordinate of the curve at parameter t.

Examples

Make a circle follow a curve

local controlPoints = {125,125, 125,225, 175,125, 225,125}
local curve         = love.math.newBezierCurve(controlPoints)

function love.draw()
	local time     = love.timer.getTime()
	local loopTime = 4
	local t        = (time / loopTime) % 1
	local x, y     = curve:evaluate(t)

	love.graphics.circle("fill", x, y, 8)
	love.graphics.line(curve:render())
end

See Also


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