Conic Scaling Bug?
I'm really surprised by the inaccuracy and disappearance of certain conics when zooming in with factors that are not very large/small. I'm talking about zoom factors in the order of 0.01.
In the past I used "Compass and Ruler". (http://en.wikipedia.org/wiki/C.a.R.)
Recently I started using GeoGebra because it has much more to offer.
I tried my examples in "Compass and Ruler" but found no problems there.
Therefore, I think it's a bug in GeoGebra.
I found a remark in the javasource "GeoConicND.java":
/** avoid very large and small coefficients for numerical stability */
protected static final double MAX_COEFFICIENT_SIZE = 100000;
Unfortunately I'm no expert on java so I can't get a quick read from the sources.
Therefore, I give some examples of things that surprise me and I hope that my findings are relevant.
I am using:
Java: Version 7 Update 45 (build 1.7.0_45-b18).
My first remark is that certain conics don't pass through points which they should do.
I'm giving an example (See attached file and press Zoom-button):
Short description of relevant construction steps.
Create conic through 5 points (Aconic).
Zoomin and see that conic doesn't pass through (0,0).
An intersection from a line with the conic stays in correct place.
SetColor[ Aconic, "Red"]
L=Line[(0, 0.002),(-0.002, 0)]