Thinking of writing a perspective tool for krita

[Brendan Scott]

On 25/04/15 19:36, Wolthera wrote:
> Sorry, the ellipse's horizontal component needs to be aligned to the
> horizon of that particular plane.
>
> There's a thread here which goes into the complexer details:
> http://www.conceptart.org/forums/showthread.php/273023-creating-a-perfect-square-in-perspective

I still don't think that gets you there. Their discussion about station
points and the degree of the ellipse for example.

I also think they're fooling themselves finding an ellipse that's tangent
to the vanishing lines. If the axis is parallel to the horizon then the
tangent to the ellipse will be perpendicular to the horizon at the end
points (so those 'tangents' actually cut inside the ellipse). You can test
this with the ellipse assistant and zoom in.

http://www.tiikoni.com/tis/view/?id=381484e

This is relevant because it means that the choice they're making about
the degree of the ellipse is arbitrary. And THAT means they are actually
eyeballing, not measuring.

For their construction method to work they would have to have the axis
of the ellipse somewhere other than the base of the vertical they have
drawn. I suspect when they're using the transform it's shifting the axis
in the process. This means the length of the axis loses its meaning (its
size should change in perspective) and they can choose among different
locations/eccentricities.

There needs to be another point (station point) to be able to identify
where the axis should move to.

> Resize your toolbox: there's a bug where it doesn't allow you to click
> transform when crop isn't touching the toolbox border.

That's hilarious. Working now. Thanks for the tip!

> For the line-tool, it's supossed to be laggy, as it takes your tablet
> sensors into account. Tick 'preview' in the tool box to get a quicker
> previewing line.

ok. I will try that.