Feature Request: Coordinate System Support for CAM

[gsdali]

Background

PadCAM generates CNC toolpaths using OCCT geometry. CAM applications require transforming between:

• CAD model coordinates (where the model is defined in OCCT space)
• G-code work coordinates (G54 space, where Z=0 at stock top)

Currently OCCTSwift provides shape-level transformations (translated, rotated, scaled, mirrored) which work well for geometry manipulation.

Feature Request

1. Coordinate System Type (Nice to Have)

A lightweight struct representing a coordinate system for CAM operations:

struct CoordinateSystem {
    let origin: SIMD3<Double>
    let xAxis: SIMD3<Double>  // Unit vector
    let yAxis: SIMD3<Double>  // Unit vector
    let zAxis: SIMD3<Double>  // Unit vector (computed: x × y)

    /// Transform point from world to this coordinate system
    func localPoint(_ worldPoint: SIMD3<Double>) -> SIMD3<Double>

    /// Transform point from this coordinate system to world
    func worldPoint(_ localPoint: SIMD3<Double>) -> SIMD3<Double>
}

Maps to OCCT's gp_Ax2 class.

2. Transform Composition (Nice to Have)

Ability to compose transformations:

extension Shape {
    /// Apply a composed transformation (translation + rotation + scale)
    func transformed(
        translation: SIMD3<Double>? = nil,
        rotationAxis: SIMD3<Double>? = nil,
        rotationAngle: Double? = nil,
        scale: Double? = nil
    ) -> Shape
}

Maps to OCCT's gp_Trsf composition.

Priority: Low

These features would be convenient but are not blocking. PadCAM can implement coordinate transformations at the application level using Swift math on SIMD3<Double> points:

// Simple CAM coordinate transform
func modelToGcode(point: SIMD3<Double>, g54Origin: SIMD3<Double>) -> SIMD3<Double> {
    return point - g54Origin
}

References

• NIST RS274NGC Standard - G54 work coordinate systems
• LinuxCNC Coordinates - Machine vs Work coordinates
• OCCT gp_Ax2 docs
• OCCT gp_Trsf docs