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When I drag a component in Altium there is always a line (sometimes it's red, sometimes it's green) connected in the center of the part and pointing to some place in the PCB. I always wonder what is this line for anyways?

enter image description here

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  • \$\begingroup\$ Off the top of my head, I think it may point to the origin where you moved the component from. You may be able to get rid of it by hitting shift + d. \$\endgroup\$ – Connor Wolf Jan 7 '13 at 5:32
  • \$\begingroup\$ They could be rat-lines / airwires. \$\endgroup\$ – Chetan Bhargava Feb 6 '13 at 6:24
  • \$\begingroup\$ @ChetanBhargava - It's not. The rat-lines are connected to the component pads. The line the OP is referring to is connected to a point at the components center. There is generally no pad at this point at all (such as in the OP's image). \$\endgroup\$ – Connor Wolf Feb 6 '13 at 6:39
  • \$\begingroup\$ @ConnorWolf I could be wrong as the last time I used an Altium product was ~15 years ago. \$\endgroup\$ – Chetan Bhargava Feb 6 '13 at 7:07
  • \$\begingroup\$ @ChetanBhargava - You are indeed incorrect. \$\endgroup\$ – Connor Wolf Feb 6 '13 at 7:07
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I asked the Altium support if there is either a way do disable this feature or to get a detailed description to understand what it does.

This is loosely translated from the German response:

If you are seeing green/red lines when placing components in the PCB document, this can be interpreted as follows: It is a kind of feedback from Altium Designer regarding the length and position of the connecting lines. Red lines indicate, that there is still a better position available with respect to intersections and connection length. Should the line show green, then this is an indication that the length of the connecting lines is well matched.

I am not really satisfied with that response but I could just disable .... oh wait.

However, there currently is no way to turn off this mode during placement.

Well, at least its a great example of implementing a feature that no-one needs because its not even documented how it works :)

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  • 1
    \$\begingroup\$ I just wished they had online examples of cases this applies so I could have a better feeling of the usefulness of this \$\endgroup\$ – mFeinstein Jun 8 '15 at 15:24
  • \$\begingroup\$ @mFeinstein: True. And considering your question was over two years old and its still not documented... There are a lot of things in general where I wonder why developers haven't complained the hell out of Altium about those. I juts started with AD a few month ago and while it has nice features it also has so many annoying things that should and could be resolved without that much effort. \$\endgroup\$ – Rev1.0 Jun 8 '15 at 20:16
  • \$\begingroup\$ Yeah, tell me about it, I would help them for free if they just cared to ask... But I don't think they are this kind of company unfortunately \$\endgroup\$ – mFeinstein Jun 8 '15 at 20:24
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It turns out that this feature (Optimal Placement Vector, or OPC) is documented in the tutorial (http://techdocs.altium.com/display/ADOH/Tutorial+-+Getting+Started+with+PCB+Design) Here's what it says. As you move a component around in the workspace, a thick green or red line will be displayed, traveling from a point within the component, to a location on the board. This line is called the Optimal Placement Vector, its function is to give an indication of whether the new location is better (green) or worse (red) than the previous location.

The vector has two distinct properties: its proposed target location; and its color.

To determine the locations for each end of the vector, the feature uses the centroid of the polygonal shape defined by the locations of the end points of the connection lines. There are 2 centroids of interest, one defined by the ends of the connection lines terminating on the component you are moving (the component centroid), the second defined by the other ends of that set of connection lines (the target location centroid).

The Optimal Placement Vector is drawn between these 2 centroids, with the component end highlighted by a dot. Because it is a relative indicator, when you first click to start moving a component the vector is always drawn in green. The 2 centroids are continuously re-calculated as you move the component, because the connection lines can move from one pad to another as they are automatically re-optimized to maintain the applicable net topology for the moving component. Because of this net re-optimization, the target end of the OPV can jump around as the component is moved. If the centroids move apart and the OPV becomes longer, it may change to red. If the centroids move closer together and the OPV becomes shorter, it may change to green.

The length of the vector is not the only condition used to set the color, the color of the OPV is also affected by the overall length of the connection lines attached to the moving component. If moving the component results in the overall length of the connection lines increasing, then the OPV becomes red. Alternatively, if moving the component results in the overall length of the connection lines decreasing, then it becomes green.

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  • \$\begingroup\$ Welcome to EE.SE. Good answer. Too bad it is 3 years late, so the OP may have moved on. \$\endgroup\$ – Sparky256 Jul 28 '16 at 17:26
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Ok, the line seems to be showing the mid-point between each end of the two net-lines, at least when dragging a two-pin device.

It seems to be part of the "Dynamic Reconnector", a term which does not appear at all even in the altium docs.

enter image description here

In any event, if you press N while actively dragging a component, it stops following the component around. However, you also loose the live net-lines.

I think the only way you're going to get more information is either wait for altium to document this feature, or contact them directly.

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It is some feature that is supposed to show you optimal routing based on component position. Like, when you put rotate a component one way, and it turns green, that's supposed to be the best position for that component. It is mostly BS, IMHO.

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