Rounded Corners: Can Anyone Explain This!?

[TravinFlavin]

Hey All,
So here's my issue. I printed a full coverage decal with a border that had to match a reused triangle aluminum sign with rounded corners. So I measured the sign and found the corner radius on paper like I've done a hundred times with rectangular signs, drew a triangle in Illustrator to the sign dimensions, entered the corner radius and printed. Then the printed corners came out twice the size of the sign!

After some trial and error I finally matched the corner radius' just to get the sign out, but this is an extremely inefficient way to do this in the future. Here's how each of the measurements came out:

Aluminum Sign's corner radius' (measured on paper): 8.1 cm;
Printed decal's corner radius' (entered at 8.1cm in Illustrator): 15.7 cm;
Final decal corner radius' after trial and error, according to Illustrator: 5.4 cm;
WTF is going on???

 

[Gino]

I don't know that system, but it appears you are calculating wrong.

 

[shoresigns]

Can you explain (or show us a drawing of) how you're measuring the radius of a round corner on a triangle? The problem is more likely you than it is Illustrator, I think.

 

[Gino]

He means like 'Yield' sign

 

[shoresigns]

He means like 'Yield' sign

Yeah, I get that. I just want to know how exactly he's measuring the radius of the corner. If you haven't done it before, and you're not very good with geometry, you could easily get confused about where the centre point of the radius is, and that would turn an 8.1 radius into a measurement of around 15.7.

Illustrator does it correctly, so I'm betting on my hypothesis.

 

[TravinFlavin]

Yeah, I get that. I just want to know how exactly he's measuring the radius of the corner. If you haven't done it before, and you're not very good with geometry, you could easily get confused about where the centre point of the radius is, and that would turn an 8.1 radius into a measurement of around 15.7.

Illustrator does it correctly, so I'm betting on my hypothesis.

Absolutely, I'm entirely aware this is likely human error. If you know how to do it properly I would really like to know!

So for rounded rectangles I'd just line up a square piece of paper to the rounded corner then measure from where the rounding begins to the point of the paper. Viola, corner radius! So I just did the same thing for the triangle, only the angles of the triangle weren't 90 degree angles, so maybe that's where the problem laid? To compensate I just cut the paper at the angle of the sign and measured that. I've attached a drawing to help illustrate. Was I totally off base there?

 

[Manevitch]

Hey All,
So here's my issue. I printed a full coverage decal with a border that had to match a reused triangle aluminum sign with rounded corners. So I measured the sign and found the corner radius on paper like I've done a hundred times with rectangular signs, drew a triangle in Illustrator to the sign dimensions, entered the corner radius and printed. Then the printed corners came out twice the size of the sign!

After some trial and error I finally matched the corner radius' just to get the sign out, but this is an extremely inefficient way to do this in the future. Here's how each of the measurements came out:

Aluminum Sign's corner radius' (measured on paper): 8.1 cm;
Printed decal's corner radius' (entered at 8.1cm in Illustrator): 15.7 cm;
Final decal corner radius' after trial and error, according to Illustrator: 5.4 cm;
WTF is going on???

That the result was twice as much points toward you measuring the diameter instead.

 

[Dan360]

It looks like the issue is your method, doing it this way in illustrator on a .8 radius on a triangle gave a result of 1.4.

I've never done anything like this before so I'm not sure about a good method, I'm leaning towards taking a photo of it square on and measuring it in illustrator.

Maybe a compass?

 

[TravinFlavin]

It looks like the issue is your method, doing it this way in illustrator on a .8 radius on a triangle gave a result of 1.4.

I've never done anything like this before so I'm not sure about a good method, I'm leaning towards taking a photo of it square on and measuring it in illustrator.

Maybe a compass?

Heh, that's that's exactly what I ended up doing, just to get it out the door. Took a few adjustments to get the print bang on. But there's GOT to be a more efficient way to do this :/

 

[Dan360]

I'm not sure about an easy method, seems like a math problem that can be avoided by using the method you ultimately did.

Here's a visual

 

[Johnny Best]

Illustrator/ effect/ stylize/ round corners, put in your radius measurement and preview to see outcome.(see thumbnail)

 

[Christian @ 2CT Media]

I always covert under 90 to true square to calculate corner radio since both Corel and Illustrator both round corners off of square.

If you draw a right angle at the outmost point of the curve and measure to the start of the curve is it the correct calculation?

 

[TravinFlavin]

Illustrator/ effect/ stylize/ round corners, put in your radius measurement and preview to see outcome.(see thumbnail)

Thanks for the reply. That's certainly helpful when matching a design on the computer, but the issue I think I'm having is measuring the correct corner radius of an acute angle from a pre-existing sign in hand.

 

[myront]

Absolutely, I'm entirely aware this is likely human error. If you know how to do it properly I would really like to know!

So for rounded rectangles I'd just line up a square piece of paper to the rounded corner then measure from where the rounding begins to the point of the paper. Viola, corner radius! So I just did the same thing for the triangle, only the angles of the triangle weren't 90 degree angles, so maybe that's where the problem laid? To compensate I just cut the paper at the angle of the sign and measured that. I've attached a drawing to help illustrate. Was I totally off base there?

As produced in CorelDRAW

 

[Propaganda Ink.]

Aluminum Sign's corner radius' (measured on paper): 8.1 cm;
Printed decal's corner radius' (entered at 8.1cm in Illustrator): 15.7 cm;
Final decal corner radius' after trial and error, according to Illustrator: 5.4 cm;
WTF is going on???

The metric system is just a theory...

 

[TravinFlavin]

As produced in CorelDRAW

That's it! Thank you!!

 

[TravinFlavin]

Thank you everyone for your input, this was driving me nuts! I KNEW there had to be a simple explanation out there. I suppose I shoulda paid more attention in geometry XD

 

[FireSprint.com]

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[ams]

Using illustrator is one of your problems, but for a radius, I usually just measure across to where both points start the curve.

 

[shoresigns]

Using illustrator is one of your problems, but for a radius, I usually just measure across to where both points start the curve.

That's called a chord. Not the same thing as a radius, and it would only work on a rounded corner with an arc of 120 degrees, i.e. on an equilateral hexagon with rounded corners.

Also, just an aside, but what on earth did Illustrator do to you that you have to cry every time someone mentions it? If you read the thread, you would see that Illustrator had nothing to do with the problem—it was a lack of understanding of math and geometry.