Calculating edgespot alignment on ceramic chips (1 Viewer)

[Toby]

I've been looking at guidance around edgespot alignment on ceramic chips, when you're creating faux spots.

I couldn't find anything on PCF that seemed to address the question, so started hunting around.

I found a thread on CT, which looks at the math (oh no!) involved, which I'm struggling to decipher.

Following are two posts originally posted by wijwij (to credit but I don't they're active anymore):

The secrets of aligned edgespots-

The math is much simpler. No need to use radians. Just use a proportion.

Let a = central angle of edge spot on face (in degrees)
Let r = radius of chip (in mm or whatever)
Let s = desired edgespot arc length (what you want to find)

Ratio of central angle / full circle = Ratio of edgespot length / full circumference

a / 360 = s / (2 x pi x r)

If you know r and a, then you just solve that proportion for s.

s = (2 x pi x r) x a / 360

If you measure r in mm then s will be in mm.

In addition, you can use the same proportion to find what central angle to use if you know the arc length of your desired edgespots. (Say, if someone wanted their edgespots to be 10 mm long and needed to find what central angle to use on the face.)

a = (360 x s) / (2 x pi x r)

Since illustration programs use degrees for angle measures, it seems to me you would want to be measuring your angles in degrees, not radians.

Once you've calculated the arc length of your edge spot, you can draw one edge spot on your rolling edge design. Then you just use the step-and-repeat feature of your illustration software to arrange the other edge spots.

In another thread, Joe suggests that for his chips, he uses a rectangle that is 128.5 mm long and 3.375 mm high for the rolling edge.

So, what value should you use in the step-and-repeat?

If you want two edge spots, use (128.5mm/2) as your value.

If you want three edge spots, use (128.5mm/3) as your value.

If you want four edge spots, use (128.5mm/4) as your value.

Etc, etc.

You don't actually have to use a calculator to figure this out. I think most illustration programs will "do the math" for you. Just type in the math expression with a slash for division. I think that works in Illustrator.


----------------------------------------------------------------

I'm having problems getting my head around the "central angle of edge spot on face (in degrees)". What is this? How is it calculated?

Is it if you drew lines from the center of the chip face circle to the edges of the spot, the angle here?

The op contained an ImageShack image, illustrating the calculation (sadly now lost).

Are there any math guys or gals out there who can advise on the formula, help visualize or explain it?

 

[Frogzilla]

is it if you drew lines from the center of the chip face circle to the edges of the spot, the angle here?

Yep.

 

[allforcharity]

Not trying to be facetious, but...

The secret of aligned edge spots is to mock up what you need in rough measurements, then hand it over to the graphic designers at the manufacturer to clean it up and provide you proofs. You're probably going to be paying an artwork fee, anyway, so get your money's worth.

But, yes, I'm pretty sure I did very similar calculations to what you did when I designed my ceramic set years ago. But I decided against faux edge spots because I wanted the full face of the chip for my main graphic. I did keep the spots on the rolling edge, but since there was nothing on the face to "align" to, I didn't have to pay that extra premium.

I also think that the prevailing wisdom at the time as that a ceramic chip should not try too hard to be a clay chip. Ceramics have their own advantages and these should be maximized.

 

[Toby]

Actually, I think the answer is self-contained:

"Ratio of central angle / full circle = Ratio of edgespot length / full circumference"

...but hopefully this is helpful information irrespective!

 

[p5woody]

Not sure if this helps

 

[Kensco]

The circumference of your chip face art is equal to the length of your chip edge art.

Divide your chip face into equal segments (16 in this example). Click on your edge art to make it the active object and then go to Object >Path >Split into Grid

In the "split into grid" window: number of column is "1" and number of rows is whatever number you split your chip into. In this example its 16. Change "Gutter" (the space between the segments) to "0". The "Width" of the segments will auto calculate. You can see the length of your edge art is already in the window labeled "Total"

(It's a good practice to make a copy of this layer first)

Color corresponding segments of the face and edge art. In this example its every other segment. You could color one, skip two. Just keep the same scheme on both surfaces.

Edit: Thanks to Sal, RIP

 

[Poker Zombie]

I made one set of ceramics, and used pi. It came out perfect.

I am proud of them, not because of the chips, but because it was the first (and so far only) time I had ever used pi. Taught to me in Jr high school, I retained it for 30+ years, apparently only for making edges on a chip.

Worth it.

 

[Venturalvn]

The trick of aligned edgespots on ceramics is...to not do continuing edgespots from the face over to the rolling edge.

Just kidding of course this is great info for anyone who wants to pursue this. But the brigade against it is large.

 

[Mental Nomad]

I have no objections to simulating edge spots on ceramics. They can look great when done well.

More important, though, you can want your art to roll over the edge cleanly even if it's not a simulating an edge spot. The math/method are the same.

Great example:

 

[BGinGA]

I have no objections to simulating edge spots on ceramics. They can look great when done well.

More important, though, you can want your art to roll over the edge cleanly even if it's not a simulating an edge spot. The math/method are the same.

Great example:

Was going to post the exact.same.response including the specific example you chose (although there are also others). Well said. (y) :thumbsup:

 

[ekricket]

Not sure if this helps

View attachment 225997

So what is the max and min arc length for Pac-Man to be able to open and close his mouth?

 

[Silverpie]

In the original game, PAC-Man's animation had three sprites.

• Sprite 1 (wide open) was 90°, so the arc length was a quarter of the circumference.
• Sprite 2 (half-open) had it at 2*arctan(7/16) or about 47°, for an arc length of about 13.1% of circumference (likely intent was 45° and 1/8 of circumference, but there are limits due to pixel resolution). The reserve-life indicators also approximate a 45° opening.
• Sprite 3 was fully closed.

Although I think I may have just given a serious answer to a non-serious question...

 

[Poker Zombie]

In the original game, PAC-Man's animation had three sprites.

• Sprite 1 (wide open) was 90°, so the arc length was a quarter of the circumference.
• Sprite 2 (half-open) had it at 2*arctan(7/16) or about 47°, for an arc length of about 13.1% of circumference (likely intent was 45° and 1/8 of circumference, but there are limits due to pixel resolution). The reserve-life indicators also approximate a 45° opening.
• Sprite 3 was fully closed.

Although I think I may have just given a serious answer to a non-serious question...

Everyone that remembers this, add +1 to your Geek Score.