# Painting with Assistants¶

The assistant system allows you to have a little help while drawing straight lines or circles.

They can function as a preview shape, or you can snap onto them with the freehand brush tool. In the tool options of free hand brush, you can toggle Snap to Assistants to turn on snapping.

The following assistants are available in Krita:

## Types¶

There are several types in Krita. You can select a type of assistant via the tool options docker.

### Ellipse¶

An assistant for drawing ellipses and circles.

This assistant consists of three points: the first two are the axis of the ellipse, and the last one is to determine its width.

- Concentric Ellipse
The same an ellipse, but allows for making ellipses that are concentric to each other.

If you press the `Shift` key while holding the first two handles, they will snap
to perfectly horizontal or vertical lines. Press the `Shift` key while holding the
third handle, and it'll snap to a perfect circle.

### Perspective¶

This ruler takes four points and creates a perspective grid.

This grid can be used with the 'perspective' sensor, which can influence brushes.

If you press the `Shift` key while holding any of the corner handles, they'll snap
to one of the other corner handles, in sets.

### Ruler¶

There are three assistants in this group:

- Ruler
Helps create a straight line between two points.

- Infinite Ruler
Extrapolates a straight line beyond the two visible points on the canvas.

- Parallel Ruler
This ruler allows you to draw a line parallel to the line between the two points anywhere on the canvas.

If you press the `Shift` key while holding the first two handles, they will snap
to perfectly horizontal or vertical lines.

### Spline¶

This assistant allows you to position and adjust four points to create a cubic bezier curve. You can then draw along the curve, snapping your brush stroke directly to the curve line. Perfect curves every time!

If you press the `Shift` key while holding the first two handles, they will snap
to perfectly horizontal or vertical lines. Press the `Shift` key while holding the
third or fourth handle, they will snap relative to the handle they are
attached to.

### Vanishing Point¶

This assistant allows you to create a vanishing point, typically used for a horizon line. A preview line is drawn and all your snapped lines are drawn to this line.

It is one point, with four helper points to align it to previously created perspective lines.

They are made and manipulated with the Assistant Tool.

If you press the `Shift` key while holding the center handle, they will snap to
perfectly horizontal or vertical lines depending on the position of
where it previously was.

バージョン 4.1 で変更: The vanishing point assistant also shows several general lines.

When you've just created, or when you've just moved a vanishing point assistant, it will be selected. This means you can modify the amount of lines shown in the tool options of the Assistant Tool.

### Fish Eye Point¶

Like the vanishing point assistant, this assistant is per a set of parallel lines in a 3d space. So to use it effectively, use two, where the second is at a 90 degrees angle of the first, and add a vanishing point to the center of both. Or combine one with a parallel ruler and a vanishing point, or even one with two vanishing points. The possibilities are quite large.

This assistant will not just give feedback/snapping between the vanishing points, but also give feedback to the relative left and right of the assistant. This is so you can use it in edge-cases like panoramas with relative ease.

If you press the `Shift` key while holding the first two handles, they will snap
to perfectly horizontal or vertical lines. Press the `Shift` key while holding the
third handle, and it'll snap to a perfect circle.

#### Tutorials¶

Check out this in depth discussion and tutorial on https://www.youtube.com/watch?v=OhEv2pw3EuI

## Setting up Krita for technical drawing-like perspectives¶

So now that you've seen the wide range of drawing assistants that Krita offers, here is an example of how using these assistants you can set up Krita for technical drawing.

This tutorial below should give you an idea of how to set up the assistants for specific types of technical views.

If you want to instead do the true projection, check out the projection category.

### Orthographic¶

Orthographic is a mode where you try to look at something from the left or the front. Typically, you try to keep everything in exact scale with each other, unlike perspective deformation.

The key assistant you want to use here is the Parallel Ruler. You can set these up horizontally or vertically, so you always have access to a Grid.

### Axonometric¶

All of these are set up using three Parallel Rulers.

- Oblique
For oblique, set two parallel rulers to horizontal and vertical, and one to an angle, representing depth.

- Dimetric & Isometric
Isometric perspective has technically all three rulers set up at 120° from each other. Except when it's game isometric, then it's a type of dimetric projection where the diagonal values are a 116.565° from the main. The latter can be easily set up by snapping the assistants to a grid.

- Trimetric
Is when all the angles are slightly different. Often looks like a slightly angled isometric.

### Linear Perspective¶

- 1 Point Perspective
A 1 point perspective is set up using 1 vanishing point, and two crossing perpendicular parallel rulers.

- 2 Point Perspective
A 2 point perspective is set up using 2 vanishing point and 1 vertical parallel ruler. Often, putting the vanishing points outside the frame a little can decrease the strength of it.

- 3 Point Perspective
A 3 point perspective is set up using 3 vanishing point rulers.

### Logic of the vanishing point¶

There's a little secret that perspective tutorials don't always tell you, and that's that a vanishing point is the point where any two parallel lines meet. This means that a 1 point perspective and 2 point perspective are virtually the same.

We can prove this via a little experiment. That good old problem: drawing a rail-road.

You are probably familiar with the problem: How to determine where the next beam is going to be, as perspective projection will make them look closer together.

Typically, the solution is to draw a line in the middle and then draw lines diagonally across. After all, those lines are parallel, meaning that the exact same distance is used.

But because they are parallel, we can use a vanishing point assistant instead, and we use the alignment handles to align it to the diagonal of the beam, and to the horizontal (here marked with red).

That diagonal can then in turn be used to determine the position of the beams:

Because any given set of lines has a vanishing point (outside of the ones flat on the view-plane), there can be an infinite amount of vanishing points in a linear perspective. Therefore, Krita allows you to set vanishing points yourself instead of forcing you to only use a few.

### Fish Eye perspective¶

Fish eye perspective works much the same as the linear perspective, the big difference being that in a fish-eye perspective, any parallel set of lines has two vanishing points, each for one side.

So, to set them up, the easiest way is one horizontal, one vertical, on the same spot, and one vanishing point assistant in the middle.

But, you can also make one horizontal one that is just as big as the other horizontal one, and put it halfway: