zoom is not smooth anymore

[ParvinEyvazov]

Description

Zoom is not smooth anymore. I have been using cap.so for more than 1.5 years now, but for the last couple of months, Zoom appears not to be smooth, but more glitchy. It is like this while in the studio (in the editor page) + after export. Not sure if it is a new form of zoom or a bug. Feel free to close this issue if it is not a bug.

Reproduction

regular recording. both in instant & studio mode

Additional Context

• Cap version: 0.4.84
• Operating system, version: mac tahoe | 26.3.1
• Device (optional): mac pro | m1 pro

cap-zoom.mp4

---

Thank you for this amazing project!!

[linear]

CAP-703

[tembo]

Looking at the codebase, the zoom smoothness is controlled by a spring-based interpolation system in crates/rendering/src/zoom.rs and crates/rendering/src/zoom_focus_interpolation.rs. The spring parameters are defined at the top of zoom.rs:

const SCREEN_SPRING_STIFFNESS: f64 = 200.0;
const SCREEN_SPRING_DAMPING: f64 = 40.0;
const SCREEN_SPRING_MASS: f64 = 2.25;

There were significant changes to the zoom rendering engine in PR #1674 (merged March 21, 2026), which rewrote cursor and zoom interpolation to use fixed-timestep spring simulations with cluster-based targeting for auto-zoom segments. Then PR #1686 (merged March 27, 2026) made additional refinements to the zoom interpolation, including continuous zoom-out transitions with ramp easing and a "gentle" cursor-visibility enforcement mode.

The instant_animation flag on ZoomSegment (in crates/project/src/configuration.rs:656) controls whether a segment uses the spring easing or instant transitions. If this is getting set unexpectedly, it would cause abrupt jumps rather than smooth transitions.

A few things worth investigating:

1. Does this occur with both auto-zoom (cursor-following) and manual zoom segments?
2. Is the glitchiness consistent throughout playback or only during certain transitions (zoom-in vs zoom-out)?
3. Does it reproduce when exporting, or only in the preview/editor?

Related issues:

• Fixed part zoom so screen does not jump up and down especially when doing 9:16 recordings and follows mouse #1401 reports similar jumpiness when zoom follows the mouse, particularly in 9:16 aspect ratio recordings
• Zoom segment handles aren't restrictive enough #289 tracks issues with zoom segment handle restrictions

The screen movement spring configuration is also exposed per-project in project_config.screen_movement_spring, which gets passed through to the ZoomFocusInterpolator in export.rs:413 and playback.rs.