Slider Crank

Unity package for simplified representation of slider crank mechanism.

Install Package

With the native Unity Package Manager, you can add https://github.com/Preliy/SliderCrank.git#upm via the Git URL or modify the Packages/manifest.json file directly.

{
    "dependencies": {
        "com.preliy.slider-crank": "https://github.com/Preliy/SliderCrank.git#upm"
    }
}

Components

SliderCrank

Add the SliderCrank.cs component to a GameObject. The transform of the GameObject represents the slider axis, and the slider moves along the Z-axis.

Parameters

• Length - The length between the wheel pin and the sliding pin (clamped to >= 0)
• Use Negative Solution - When enabled, uses the negative solution for the slider position calculation

References

• Pin - Transform reference to the pin (wheel pin)
• Slider - Transform reference to the slider

Settings

• Update Type - Select when to perform the calculation:
  • Update - Calculates in Update() loop
  • FixedUpdate - Calculates in FixedUpdate() loop
  • LateUpdate - Calculates in LateUpdate() loop
• Execute in Editor - When enabled, calculations are executed in the editor and the slider position is updated
• Show Gizmos - Displays visualization gizmos in the Scene view

---

MoveCrank

Add the MoveCrank.cs component to a GameObject to control crank movement using triangle geometry calculations.

Parameters

• Length AC - The length of side AC in the triangle formed by points A, B, and C

Control

• Execute - When enabled, the component actively updates the crank position

References

• Flip Side - When enabled, flips the angle calculation to the opposite side
• A - Transform reference to point A
• B - Transform reference to point B
• C - Transform reference to point C (this is the point that gets repositioned)

Gizmos

• Show Gizmos - Displays visualization gizmos in the Scene view:
  • Red spheres at points A, B, and C
  • Cyan line from A to B and B to C
  • Yellow line from C to A
  • Cyan wire disc showing the rotation arc around point B

Notes

• The component uses the law of cosines to calculate triangle angles
• It validates triangle inequality to ensure valid triangle geometry
• Point C is repositioned based on the calculated angle at point B
• Rotation is performed around the transform's right axis

---

Demo

In Samples/Demo you can find a demo scene with examples of both components in action.