--- key: mechanic/trackpad--family-07 type: mechanic id: trackpad--family-07 lang: en title: Multiple Contact Geometry summary: >- Finger separation changes scale. Pinching zooms a document in Preview; the app may receive a recognised gesture instead of two contact coordinates. updatedAt: '2026-10-22' status: active url: 'https://gamemechanics.pro/en/knowledge/mechanic/trackpad--family-07/' jsonUrl: >- https://gamemechanics.pro/api/v1/knowledge/en/mechanic/trackpad--family-07.json markdownUrl: 'https://gamemechanics.pro/content/knowledge/en/mechanic/trackpad--family-07.md' aliases: [] tags: - Trackpad interactions - Mechanics catalog sourceIds: - source-0d7ed8efcd920b62 - source-7641af4e83c63a96 - source-80fb36760a664f26 - source-2aa43929eb995c4c sources: - id: source-0d7ed8efcd920b62 title: macOS Gestures url: 'https://support.apple.com/en-us/102482' verifiedAt: null - id: source-7641af4e83c63a96 title: Windows Gestures url: >- https://support.microsoft.com/en-us/windows/hardware/input-devices/touch-gestures-for-windows verifiedAt: null - id: source-80fb36760a664f26 title: 'AppKit: contacts and system gestures' url: >- https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/EventOverview/HandlingTouchEvents/HandlingTouchEvents.html verifiedAt: null - id: source-2aa43929eb995c4c title: Preview (macOS) url: >- https://support.apple.com/guide/preview/view-pdfs-and-images-prvw11470/11.0/mac/26 verifiedAt: null relations: [] placements: - catalogId: trackpad id: family-07 title: Trackpad interactions url: 'https://gamemechanics.pro/en/mechanics/trackpad/#family-07' categoryIds: - section-1 supersededBy: [] attributes: preview: updatedAt: '2026-10-22' title: Multiple Contact Geometry description: >- Finger separation changes scale. Pinching zooms a document in Preview; the app may receive a recognised gesture instead of two contact coordinates. image: src: images/mechanics/control-macos-preview.webp width: 788 height: 750 game: Preview (macOS) sourceUrl: >- https://support.apple.com/guide/preview/view-pdfs-and-images-prvw11470/11.0/mac/26 originalUrl: >- https://help.apple.com/assets/67DB77BFAE89A3DDC700A869/67DB77C0E2208881620C3D38/en_US/918f957676bf215f21f57328147e8435.png credit: Apple rights: >- © Apple. Official support screenshot; all rights reserved. Excluded from MIT and CC BY 4.0. caption: 'Preview: page scale changes with a pinch or toolbar controls' alt: 'Preview: page scale changes with a pinch or toolbar controls' markers: - x: 80 'y': 4 label: Zoom controls provide an alternative to a two-finger gesture tips: - >- Do not promise finger coordinates when the API only supplies a zoom gesture. examples: - title: Preview (macOS) url: >- https://support.apple.com/guide/preview/view-pdfs-and-images-prvw11470/11.0/mac/26 endsAt: null provenance: >- Original editorial design catalog consolidated from project discussions on 2026-10-20. Complete discussion item lists and contextual limitations are preserved; linked primary sources support specific techniques, not the entire classification. English translation was prepared with machine assistance and editorial review. license: CC-BY-4.0 codeLicense: MIT attribution: gamemechanics.pro contributors catalogKey: catalog/trackpad --- # Multiple Contact Geometry id: trackpad--family-07 type: mechanic key: mechanic/trackpad--family-07 lang: en status: active url: https://gamemechanics.pro/en/knowledge/mechanic/trackpad--family-07/ Finger separation changes scale. Pinching zooms a document in Preview; the app may receive a recognised gesture instead of two contact coordinates. ## At a glance ![Preview: page scale changes with a pinch or toolbar controls](https://gamemechanics.pro/images/mechanics/control-macos-preview.webp) [Preview (macOS)](https://support.apple.com/guide/preview/view-pdfs-and-images-prvw11470/11.0/mac/26) · © Apple. Official support screenshot; all rights reserved. Excluded from MIT and CC BY 4.0. 1. Zoom controls provide an alternative to a two-finger gesture - Do not promise finger coordinates when the API only supplies a zoom gesture. - [Preview (macOS)](https://support.apple.com/guide/preview/view-pdfs-and-images-prvw11470/11.0/mac/26) ## How it works The relative positions of multiple contacts define scale, angle, and other geometric parameters; you need access to this data. ## Variants ### Variants and applications - Bringing two fingers together. Gesture: Reduce the distance between contacts. In the interface: Zoom out, go to overview. In the game: Move the map away or shrink the game object. Access level: Ready gesture; You need a gesture transmitted by the OS or framework: scroll, zoom, rotate, swipe or hold. The set varies. Conditions: From a ready-made pinch the scale is often available, but not the coordinates of both points. - Spreading two fingers. Gesture: Increase the distance between contacts. In the interface: Zooming in, revealing details. In the game: Enlarging the map, stretching the spring, opening the shield. Access level: Ready gesture; You need a gesture transmitted by the OS or framework: scroll, zoom, rotate, swipe or hold. The set differs. Conditions: To physically simulate both grips, T. is required. - Two finger rotation. Gesture: Change the angle of the line between contacts. In the interface: Rotate an image, canvas or model. In the game: Valve, part orientation, rotate an artifact. Access level: Ready gesture; You need a gesture transmitted by the OS or framework: scroll, zoom, rotate, swipe or hold. The set varies. Conditions: Rotate support does not automatically follow from the presence of pinch. - Simultaneous translation, scale and rotation. Gesture: Move the center, change the distance and angle of the pair. In the interface: Free transformation of an object or canvas. In the game: Installing a part, manipulating a card or mechanism. Access level: Ready gesture; You need a gesture transmitted by the OS or framework: scroll, zoom, rotate, swipe or hold. The set varies. Conditions: The framework must allow joint recognition. Otherwise, you need T and your own handler. - One finger is like an anchor. Gesture: Leave the contact motionless, the second change the radius or angle. In the interface: Transformation relative to an explicit reference point. In the game: Lever, compass, winding the cable, sight around the support. Access level: Individual contacts; You need access to coordinates, phases and contact IDs. The presence of multitouch on the device does not guarantee this. Conditions: A ready-made scale or rotation may not be enough: both coordinates are needed. - Two independent grips. Gesture: Each contact controls a separate end of an object. In the interface: Editing a segment, range or connection. In the game: Pull a rope, hold two handles, place a bridge. Access level: Individual contacts; You need access to coordinates, phases and contact IDs. Having multitouch on a device does not guarantee this. Conditions: The application must preserve contact roles and handle the disappearance of one of them. - Stretch along the selected axis. Gesture: Use a separate change in horizontal or vertical distance. In the interface: Disproportional size, width and height. In the game: Shrink an obstacle, stretch a passage or platform. Access level: Separate contacts; You need access to coordinates, phases and contact IDs. The presence of multitouch on the device does not guarantee this. Conditions: A regular scalar pinch does not report the full geometry of the pair. - Deformation along three supports. Gesture: Change shape or affine transformation with three tracked points. In the interface: Tilt, shift, deform the mesh. In the game: Bend a soft body, control three fasteners. Access level: Individual contacts; You need access to coordinates, phases and contact IDs. The presence of multitouch on the device does not guarantee this. Conditions: Three independent coordinates are needed. Two points are not enough for an unambiguous general shear transformation. - Spreading a group of fingers. Gesture: Increase the spread of three or more contacts. In the interface: Expand a group, expand a structure. In the game: Scatter a squad, reveal a device or field. Access level: Individual contacts; You need access to coordinates, phases and contact IDs. The presence of multitouch on the device does not guarantee this. Conditions: May coincide with the global OS gesture; interception verification and number of contacts are required. - Bringing together a group of fingers. Gesture: Collect multiple contacts to a common center. In the interface: Collapse a group or move to a common structure. In the game: Collect objects, compress an area, concentrate energy. Access level: Individual contacts; You need access to coordinates, phases and contact IDs. The presence of multitouch on a device does not guarantee this. Conditions: Do not assume that each finger has an independent force measurement or a known anatomical role. ## Context and limits Author's working classification for designing games and interactions. Options can overlap and combine; the list is not a generally accepted standard or proven exhaustive list. Application examples are conditional unless a specific verifiable observation is indicated nearby. Sources support individual techniques and technical limitations. ## Connected materials ## Sources and provenance Original editorial design catalog consolidated from project discussions on 2026-10-20. Complete discussion item lists and contextual limitations are preserved; linked primary sources support specific techniques, not the entire classification. English translation was prepared with machine assistance and editorial review. - [macOS Gestures](https://support.apple.com/en-us/102482) (id: source-0d7ed8efcd920b62) - [Windows Gestures](https://support.microsoft.com/en-us/windows/hardware/input-devices/touch-gestures-for-windows) (id: source-7641af4e83c63a96) - [AppKit: contacts and system gestures](https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/EventOverview/HandlingTouchEvents/HandlingTouchEvents.html) (id: source-80fb36760a664f26) - [Preview (macOS)](https://support.apple.com/guide/preview/view-pdfs-and-images-prvw11470/11.0/mac/26) (id: source-2aa43929eb995c4c) CC-BY-4.0 · gamemechanics.pro contributors