Sketchup -- How to Draw Lines Tangent to a Circle

Introduction: Sketchup -- How to Draw Lines Tangent to a Circle

Sketchup doesn't have a function that allows you to draw tangent lines to a circle so you have to do it the old school geometry way. Here is how.

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    3 Discussions


    4 years ago

    Good method but what if it was 1 3/16" X 2 31/64"?


    5 years ago on Introduction

    I appreciate the video. Sketchup gets a large user-base
    because its free, but it sucks it requires so many workarounds to achieve basic
    results, as you demonstrate. I use it and it has its purpose. Its purpose is to
    have reasonable 3D presentations for basic uses but it is not and cannot be
    accurate. It is completely unusable for any purpose where 10ths, hundredths, or
    thousands of an inch matter.

    Sketchup was designed badly from its inception. At its core,
    is flawed math. Whenever you draw a circle in Sketchup, mathematically, any
    circle/arc is immediately translated into straight line segments. I design
    parts and assemblies and it was very disappointing to realize it’s impossible
    to draw anything with accuracy using Sketchup.

    It got worse when I realized it’s hard-coded into 24
    segments per circle. While Sketchup does allow the user to manually change the
    number of segments, that feature is worthless as it breaks all the internal
    math calculations for creating faces, trimming at intersections, or, frankly,
    anything normal in making a drawing. A user is stuck with 24 segments per 360
    degrees or, if you change the number of segments, you will soon learn how Sketchup
    breaks down.

    It is also broken with its hiding feature. Incessantly, I
    hide groups or components only to discover the auto-trimming and/or auto
    creation of faces and/or multiple other features are affected by objects that
    are hidden or already moved. For example, I havea group in the background with arc segments
    and not only should Sketchup not trim my newly designed lines/arcs using
    elements from a group (its supposedly
    designed in behavior), but I also find my elements are continuously
    trimmed/modified by elements that are hidden.

    I hope my comments don't get reflected badly on you (they
    shouldn't). I appreciate all your effort to help with creating lines from
    tangent to tangent. You’re doing the only method that will work in Sketchup and
    it is very helpful. I wish you would show users what happens when you create a
    solid by clicking "closely" as you described at the beginning. Yet
    another bad feature of Sketchup is that it does NOT ensure closed endpoints.
    When you click closely, there is really a gap. That gap doesn't stop Sketchup
    from allowing planes to be created (the drawing appears okay graphically), but
    the gap does cause numerous features to break; especially those related to

    For example, if you try to use the join or subtract features
    they, very often, fail. I have experienced crazy bending/warping, inner
    contours that can't have their planes deleted, or I couldn’t join two solids simply
    because they are broken in some undiscoverable way without a plugin helper like
    “Solid Helper2”.

    To be honest, Sketchup is simply not a professional software
    product. It is impossible to design anything with accuracy and it’s loaded with
    buggy/limited features.

    NOTE: Having said that, the free version can be very useful
    and its very helpful to a great number of people who don't have money. It’s
    really not bad for something that is free. It is not worthy of the Google name.

    Seriously, thanks for assisting, it does take crazy stuff
    like your example to draw basic shapes, but knowing these type of tips/tricks
    allows the product to be more useful. I do hate that it’s impossible for
    Sketchup to ever be a truly professional product (IMO) as the core engine is
    mathematically flawed, but I do still use it knowing all its problems.

    Thanks again and sorry if I want other users to be
    wary/careful of using it. It’s truly not a professional grade product and
    cannot possibly be professional grade the way it mathematically works
    under-the-hood. That is why it doesn't support simple features like snapping to
    a tangent. The math formula that calculates a tangent requires a true arc or
    circle's dimensions. A series of straight line segments simply don't have the
    information required to allow that kind of feature to work. It’s also why it
    doesn't have a fillet option or chamfer options or any of many options that robust
    3D/CAD systems offer. In summary, it’s a useful toy under the right
    circumstances and the word pro belongs nowhere near it.

    Solidworks is the real deal for actual real-life production
    purposes. For gaming or other purposes, there is a long list that are the real
    deal, but that's not my territory. Again, for real-life professional purposes,
    get Solidworks, or AutoCAD Inventor. Inventor LT is far superior to Sketchup
    and costs less than Sketchup Pro.