Display issue with arc commands (G02/G03) drawing the wrong way

I am a frequent user/admin in another forum where repetier host is used by a lot of users. There is a simple bug that has shown up quite a few times. I haven't used RH for a while myself, but I decided to write about this issue to make sure the devs are aware of it.

It seems pretty obvious to me that the issue is that G02 and G03 commands are being interpreted the wrong way (they are going the wrong direction, clockwise vs anticlockwise) since version 2.2.3/2.2.4. The gcode plays fine on the machine, but the RH preview is wrong.

The most common firmware is Marlin over there, but grbl is popular too.

Here is an example (you shouldn't have to log in to see the images:


  • Yes it is on my list. There are some edge cases where some parameter get wrong. Since 0.1° is gets 350.9° in other direction and you see all these circles.
  • ok. Cool. Thanks for the tool. I'm glad you have your eyes on this issue.

    I have used code like this to get back in the range of -pi to pi:

        angle = (angle+2*PI) % 2*PI // This gets it between [0,PI]
        if (angle > PI)
          angle = angle - 2*PI

  • That's not actually the issue. Issue is if moves are very tiny you need to decide if user wanted a 360° circle or a tiny circle segment that is more like a line. As always with rounding error ranges any "bad" decision later shows up. But "bad" sometimes also depends on what user wanted.
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