Fisheye Perspective Ruler

This ruler was added in version 17.01.06. Some sub-features were added in later updates.

Whereas linear perspective projects straight 3d lines to straight 2d lines, fisheye perspective projects them to curved 2d lines. This perspective mode has a fixed field of view of 180°. Half of the world (what's in front of the viewer) is effectively projected onto the view circle.

This ruler has three guide lines that connect your current pen position to the vanishing points, helping you draw perspective-correct objects anywhere in your scene.

1. Canvas Zoom

This parameter was named Image Zoom in older versions.

If you are using LNP with a version of Photoshop older than CS3, or with any other art application, you must set this parameter to match the value of your canvas zoom after you zoom in or out. You then need to realign the ruler or the perspective lines will no longer align with your scene. The easiest way to do this is to draw a mark under the view center point in a separate layer, so that you can quickly realign it with the view center when needed.

When working on an image over multiple sessions, you will have to realign the ruler when you open your document again. Starting with version 21.02.15, the ruler center position within your Photoshop canvas is now stored in your LNP preset along with the other ruler parameters when you save your preset, or save it as a new preset.

With Photoshop CS3 and up, your document's pan and zoom will be tracked automatically (this was added in LNP update 18.03.08). In this case, you do not need to change the Canvas Zoom parameter yourself (it will have no effect).

For apps where automatic tracking is not possible, you can at least enable the Settings/Spacebar Pan Offsets Ruler Centers menu to keep your center aligned while you pan your canvas (in Photoshop, be sure to uncheck Enable Flick Panning in the general preferences tab).

2. View Radius

This is the first parameter you should adjust when setting up for a new perspective scene. It defines the radius (in screen-space pixels) of the circle onto which a 180° view of the world is projected. The size of the radius will depend on how much of the world view you want on your canvas. If you're not sure what you want, set this parameter so that the view circle covers most of your canvas at 100% zoom.

The circle itself can be placed by dragging the center control point while holding the control key, or by using the Move Center keyboard shortcut.

3. Horizon Tilt

This feature was added in version 20.05.15.

This parameter controls the camera roll, or rotation around the Z axis. You can also change it by dragging the green control point while holding the control key.

This can be used to compose Dutch Angle shots, which can portray disorientation, psychological uneasiness, or tension in the subject being filmed or photographed.

It can also be used to rotate the first two vanishing lines around the Z axis, helping you place rotated objects in your scene.

4. View Tilt

This feature was added in version 20.07.07.

This parameter controls the vertical tilt of the line of sight. It corresponds to the camera's angle of rotation around the X axis, and directly controls the orientation of the vertical guide line, and the curve of the horizon. You can also change it by dragging the green control point on the vertical line while holding the control key.

5. Line 1&2 Angle and Tilt

This feature was added in version 20.07.07.

These parameters control the angles of the first two perspective guide lines. Contrary to the vertical guide line (controlled via View Tilt), these are primarily used for drawing lines that are parallel to the ground. They are defined by their angle on the ground plane with respect to the line of sight (Z axis). You can change these by dragging the green control points on the guide lines while holding the control key.

Controlling the guide lines via their 3d angles allows you to place rotated shapes anywhere in your scene, without worrying about where the actual vanishing points should be placed. For example, if you want to draw a square, the only requirement is that the difference between Line 1 and Line 2 angles is 90. But they can be rotated any way you like: -45/45, -30/60, -10/80, etc. If you have the Angle Link button checked, the angle difference will be locked, allowing you to rotate both lines at the same time while interacting with one.

The blue control points can be used to set the vertical tilt angles of the lines. This can be used to draw inclined surfaces, such as roofs and ramps.

6. Line Select Mode

The Line Select Mode parameter determines which guide line is chosen when you draw:

• Manual start & change: You have to manually choose which guide line to start drawing on by pressing the shift key. You can change lines while drawing by pressing the control key.
• Auto start, manual change: The starting guide line will be chosen automatically based on the direction of the first few samples of your line. You can change directions while drawing by pressing the control key.

Being able to change direction without lifting your pen helps you get perfect corners!

7. Box Mode

This feature was added in version 20.07.07.

When this is enabled, your pen position will be constrained to a 3d bounding box while you draw, helping you quickly draw perfect boxes without lifting the pen and without your lines overshooting at the corners. The dimensions of the box are determined automatically one at a time as you first draw on each axis (press control to change direction).

When set, the box sections of the vanishing lines will turn orange. The dimensions are reset when you lift the pen.

When you draw along a tilted line, this line will be treated as the diagonal of a triangle, and so box mode will automatically set the lengths for the horizontal and vertical projections. This will help you quickly close the triangle.

8. Fixed Axes

Holding the control key will display the yellow tick distance control point, and the pink Fixed Axes toggle control point (previously named Freeze Mode).

Clicking on the Fixed Axes control point (or pressing the associated keyboard shortcut) will create a fixed frame of reference at your pen position. Like with the Isometric, Vanishing Lines, and Linear Perspective rulers, you can use this and the measure points to accurately construct and compare object scales, and subdivide sections.