Hey Aaron, the machine doesn't know the position of the paper at all - it doesn't really have any concept of margins or anything, it doesn't even really have a concept of a home point.

The _controller_ does have a page though, and it's mostly just for a visual guide for helping you layout and place your images.

It's got four properties configured to display
page size (in mm)
controller.page.width
controller.page.height

and then position of the page, relative to the top-left corner of the machine (in mm):
controller.page.position.x
controller.page.position.y

HOWEVER, the other function that the page position serves is to define the home point in the controller.

The home point is the point where the line down the middle of the machine intersects with the top edge of the page in the controller. So the value of controller.page.position.y defines how far down the machine the home point is. It's 120mm by default, but you might have changed it if you've moved the page. (It doesn't really matter where it is as long as your machine is strong enough to hold the gondola there.)

So when you draw your lines on your actual machine, your home point must be the same distance from the top as you have set in your properties file for (that is, the value of controller.page.position.y).

This will coincide with the top edge of the page in the controller.

The purpose of this all is to be able to set the lengths of the cords to a known value. When you do a "set home" command, that's all it does - works out the length the cords need to be to reach the home point in the controller, then tells the machine that they _are_ that length. It's our job to make sure that the physical setup reflects that.

Any use?

Sandy Noble

I'm unsure about what makes the difference between a bleedy pen and a non-bleedy pen. So far, it seems to be that water-based pens don't bleed, and spirit-based pens are bleedy. Every now and again though, I get a bleedy water based fineliner, and a spirit based pen that behaves. Go figure.

Aha, well that's less easily fixed. Trial and error I'm afraid. I usually have about 4 to 6mm peeping out of the end of the tube. If it's too little, then the stabiliser pulls the pen tip off the surface when it moves, if it's too long then your corner quality will suffer because the tip will drag around after the gondola itself. Just a matter of tuning.

I find there's patches on the page where the pen is more or less likely to lift - never figured out a rationale for why or where, but near the bottom is bad - when the V of the cord is at a very shallow angle the gondola tends to swing around on the tip more violently, and it's more likely to come off then.

Slowing down acceleration and max speed is another solution to most of those problems - if you aren't in a hurry. And lets face it, if you've got a polargraph machine, then you aren't in a hurry.

cheers!
sn

Ah, blu-tack. Clever stuff.