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  1. #1
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    Default Full Scale Adjustable Printable Bézier Curve Templates

    I've just added full scale Bezier Curve template generators to blocklayer.com, to mark out uneven curves.
    Printable Adjustable Full Scale BĂ©zier Curve Templates - Metric

    Drag sliders to change width, height and shape of the curve, then print at 100% printer scale to mark it out.
    The dimensions are marked on the animated diagram.
    You can also left click, release and drag inside the template to measure actual 100% scale dimensions.

    Please let me know if it needs additions, editing or fixing in any way.

    bezier.jpg

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  3. #2
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    back in Alberta for a while
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    Thank you for that, but ...

    to my eye something is not quite right.
    with X centered on the width, and the height set to half the width or less, the bezier, and it's base line, should approximate a chord and the subtended arc.

    Also, the bezier definition I'm most familiar with allows for the tangent at the end points to be adjusted independently of each other, and it's the adjustment of the end point tangents which defines the curve's height and "center", not the way it's defined in your app.
    regards from Alberta, Canada

    ian

  4. #3
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    Quote Originally Posted by ian View Post
    to my eye something is not quite right.
    with X centered on the width, and the height set to half the width or less, the bezier, and it's base line, should approximate a chord and the subtended arc.

    Also, the bezier definition I'm most familiar with allows for the tangent at the end points to be adjusted independently of each other, and it's the adjustment of the end point tangents which defines the curve's height and "center", not the way it's defined in your app.
    The template generator uses a quadratic Bézier curve (as defined https://www.w3schools.com/tags/canva...ticcurveto.asp ) which only has 2 control points, as opposed to a cubic Bézier curve, which has 3:
    From the reference site: A quadratic Bézier curve requires two points. The first point is a control point that is used in the quadratic Bézier calculation and the second point is the ending point for the curve.
    You can play round with the coordinates in the above reference site here: https://www.w3schools.com/tags/tryit...adraticcurveto

    I chose this because it's easier to define for a simple curve. (Less points / sliders to set)
    The cubic Bézier is defined here: https://www.w3schools.com/tags/canvas_beziercurveto.asp

    Does that explain the discrepancies you're seeing? (or have I got something else wrong)

    I'll take a look at adding the cubic version as well.

  5. #4
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    Default

    Nice website, Bookmarked!

  6. #5
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    back in Alberta for a while
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    Default

    Quote Originally Posted by Blocklayer View Post
    The template generator uses a quadratic Bézier curve (as defined https://www.w3schools.com/tags/canva...ticcurveto.asp ) which only has 2 control points, as opposed to a cubic Bézier curve, which has 3:
    From the reference site: A quadratic Bézier curve requires two points. The first point is a control point that is used in the quadratic Bézier calculation and the second point is the ending point for the curve.
    You can play round with the coordinates in the above reference site here: https://www.w3schools.com/tags/tryit...adraticcurveto

    I chose this because it's easier to define for a simple curve. (Less points / sliders to set)

    Does that explain the discrepancies you're seeing? (or have I got something else wrong)
    as you say the quadratic Bézier requires 2 control points, x(0),y(0) and x(1),y(1).

    not wrong but...
    the way you have built the application,
    x(1) = x(0) + the value on the 'x' slider.
    y(1) = y(0), in the general quadratic case y(1) and y(0) can have different values, and y(1) can be less than y(0) and also less than zero.

    in the linked web page,
    the starting point of the curve appears to be defined by the function ctx.moveTo(x(0), y(0))
    the shape of the curve appears to be defined by the function ctx.quadraticCurveTo('variable1', 'variable2', x(1), y(1))

    I'm not sure what 'variable1' and 'variable2' define, but some values result in a Bézier where some part of the curve is in the space to the left of x(0) and depending on the value of 'variable2' the resultant Bézier can be above or below the straight line connecting x(0),y(0) and x(1),y(1).

    or am I missing something?
    regards from Alberta, Canada

    ian

  7. #6
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    Default

    The template generator sliders only change the total length, and the Y and X points to control the shape of the curve.
    The start and end points on the Y axis remain at 0 (top of bounding rectangle) so the curve starts and ends at the top edges of the bounding rectangle.
    A negative value for the X slider (or less than the starting X) would push the curve to the left of its starting point, and a value for X greater than the ending X would push it to the right of its end point.
    But I wanted to keep it a simple curve that fits inside a bounding rectangle, with as few 'settings' as possible.
    I'll add a few extra controls and options for the curve to a test version, and see what comes about.
    Thanks for the input.

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