Intro

This is a meta-issue to collect thoughts about implementing axes.

Axes are important for downstream code like Fastplotlib. I think it makes sense to support the building blocks in pygfx itself, so that axes can be composed and configured with relative ease.

Tasks

• Grid object #743
• Add Ruler object #787
• Better markers (instead of dots).
• Use a single text object in the ruler.
• Rotated tick marks.
• The ruler has a delay due to controller damping. Ref Update propagation #495
• Ruler support function to transform tick value to custom repr.

Things that make up axes

Strict:

• Viewport (in 2D the axes is drawn over/around the scene).
• Lines for the axes.
• Ticks.
• Tick labels.
• Grid.

Somewhat broader:

• Title, x-label, y-label.
• Legend.
• Colorbar.
• UI elements.

Things to solve or account for

• Tick spacing.
• Log scale.
• Polar scale.
• Map projection.
• Layout (i.e. positioning title and labels)
• Twin axes (Left and right side with diff y-scales)

Links

Related issues and prs:

• Proposal for renderer / viewport improvements #492
• Camera.show_object() often has large margins #683
• Responsibility of the Scene object #582
• Support map projections #118
• Improve support for custom tick formatting #831

Techniques:

• Nicolas' shaders for infinite grids: https://jcgt.org/published/0003/04/01/

Implementations:

• Axis in visvis
• Axis in vispy

Example from visvis (we can do better 😉):

Example from vispy:

I will update this text as I collect more info and converge on a plan.