# Thinking of writing a perspective tool for krita

Wolthera griffinvalley at gmail.com
Fri Apr 24 14:59:42 UTC 2015

```I see.

The reason the vanishing point assistant was set up the way it was is
because of the way I understand perspective: All parallel lines share a
single vanishing point, and making the horizon is actually a lot easier
than you'd think: Just turn on snapping and draw a line from one vanishing
point to the other. (Though shift+snapping is on my todo list for the
parallel lines :) )

As far as I know I wasn't eyeballing the distances: You can check these by
drawing diagonals, and maybe I haven't drawn enough diagonals in the video
itself. It was my third take or something, but I did take into account the
diagonals.

But, in regards to that link: let me make your life a whole lot more easy:
A perfect circle in perspective is always an ellipse. An ellipse in
perspective in turn becomes an egg-shaped ellipsoid. What's more, any
perfect circle fits perfectly in a perfect square. What this means is that,
if any given perfect circle is an ellipse, we can draw our lines around it,
then we have a perfect square! I'm attaching an image with this in Krita.
Sounds a lot easier than following that link's guide for a perfect square
each and every time, doesn't it?

Similarly, you can use the perspective transform to deform any given
imagine to a perspective plane(you can even drag around the vanishing
points in the perspective transform for precision).(This isn't cheating,
Krita isn't a videogame)

You can use the distance measure tool to measure pixels. In the future I
hope to get a concentric circle assistant working, which you could then use
to draw a perfect circle around each vanishing point so you don't have to
go and measure things.

I hope this e-mail doesn't sound flippant, but I want to make your life
easier, or at the least bearable till I have time to work on the assistants
again. :)

On Fri, Apr 24, 2015 at 4:05 PM, Brendan Scott <
disposableemail at apps.opensourcelaw.biz> wrote:

> On 24/04/15 15:59, Wolthera wrote:
>
>> No, sorry. Python support is something we really want to get in, but
>> there's been no funding to pay for the necessary time we need to dedicate
>> to it.
>>
>> As for the perspective tool, I understand the perspectice grid is a bit
>> difficult to use, but we also have several tools in the assistants:
>>
>> Or were you thinking of something else entirely?
>>
>
> I think the assistants are awesome. In fact I built my own copy of 2.9(.2)
> just
> to try them and can see lots of places where they would be useful.
>
> What I was thinking about is:
>
> * In 2 point perspective it's pretty standard to have a horizon line.
> There's
> no easy way to set up two points on a horizon line - for example it's hard
> to be sure that the assistant is even horizontal (shift will work for
> normal
> lines, but not apparently for the assistants). This is probably my main
> issue
> atm.
>
> * In the drawing of the church the artist was "eyeballing" the distances.
> There
> is no (easy) way to check the correspondence between distances in each of
> the
> axes established by the perspective view. That is, the assistants allow
> you to create a
> rectangular prism in perspective space but there's no simple way of
> ensuring that
> sides on different axes are of equal length (eg: can't draw a perspective
> cube).
> This is achieved through the use of measuring points and a distance point.
>
> See the process explained here:
>
> http://architecturerevived.blogspot.com.au/2014/01/how-to-draw-perfect-cube-in-perspective.html
>
> To create these you need to be able to measure pixel distances (to set the
> measure points) and right angles (to get a point called a distance point
> from which
> the measure points can be calculated). Short of putting a set square up
> against my
> monitor I couldn't see how I could get this point through Krita (I could
> "eyeball"
> it I guess but it seems it should be easier).
>
>
> Thanks
>
>
> Brendan
>
>
> _______________________________________________
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>

--
Wolthera
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