UVtools/UVtools.Core/Slicer/LinAlgUtils.cs

/*
 *                     GNU AFFERO GENERAL PUBLIC LICENSE
 *                       Version 3, 19 November 2007
 *  Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
 *  Everyone is permitted to copy and distribute verbatim copies
 *  of this license document, but changing it is not allowed.
 */

namespace UVtools.Core.Slicer;

public static class LinAlgUtils
{
    /*#region Find Facets
    public static List<Facet> FindFacetsIntersectingZIndex(STLDocument stl, float z)
    {
        return stl.Facets.Where(f => f.Vertices.Any(v => v.Z <= z) && f.Vertices.Any(v => v.Z >= z) && Math.Abs(f.Normal.Z) != 1).ToList();
    }

    public static List<Facet> FindFlatFacetsAtZIndex(STLDocument stl, float z)
    {
        return stl.Facets.Where(f => f.Vertices.All(v => v.Z == z)).ToList();
    }

    public static List<Facet> FindTopFlatFacetsAtZIndex(STLDocument stl, float z)
    {
        return stl.Facets.Where(f => f.Vertices.Any(v => v.Z == z) && f.Normal.Z == 1).ToList();
    }
    public static List<Facet> FindBottomFlatFacetsAtZIndex(STLDocument stl, float z)
    {
        return stl.Facets.Where(f => f.Vertices.Any(v => v.Z == z) && f.Normal.Z == -1).ToList();
    }
    #endregion

    public static SliceLine CreateLineFromFacetAtZIndex(Facet facet, float z)
    {
        // This won't work for flat horizontal plane vertices, so throw if that's what we've got
        if (Math.Abs(facet.Normal.Z) == 1)
            throw new Exception("Cannot create lines for flat horizontal planes");
        var verts = facet.Vertices;
        var returnLine = new SliceLine();
        // If any vertices are ON the z-index, just return that line
        returnLine.AddRange(verts.Where(v => v.Z == z).Select(v => new PointF(v.X, v.Y)));
        // For uniformity, I'm representing a point as a "line" between two of the same point
        // It's janky, I'll refactor later
        if (returnLine.Count == 1)
        {
            returnLine.Add(returnLine[0]);
        }
        if (returnLine.Count == 2)
        {
            returnLine.Normal = new PointF(facet.Normal.X, facet.Normal.Y);
            return returnLine;
        }
        // If no vertices are ON the z-index, find the two points where they CROSS it
        if ((verts[0].Z - z) / (verts[1].Z - z) < 0)
            returnLine.Add(CalculateZIntercept(verts[0], verts[1], z));
        if ((verts[2].Z - z) / (verts[1].Z - z) < 0)
            returnLine.Add(CalculateZIntercept(verts[2], verts[1], z));

        if (returnLine.Count < 2)
            returnLine.Add(CalculateZIntercept(verts[0], verts[2], z));

        returnLine.Normal = new PointF(facet.Normal.X, facet.Normal.Y);

        if (!returnLine.Validate())
            throw new InvalidOperationException("Invalid Point Data");

        return returnLine;
    }

    public static PointF CalculateZIntercept(Vector3 v1, Vector3 v2, float z)
    {
        var returnX = CalculateDimensionalValueAtIndex(new PointF(v1.Z, v1.X), new PointF(v2.Z, v2.X), z);
        var returnY = CalculateDimensionalValueAtIndex(new PointF(v1.Z, v1.Y), new PointF(v2.Z, v2.Y), z);
        return new PointF
        {
            X = returnX,
            Y = returnY
        };
    }

    public static float CalculateDimensionalValueAtIndex(PointF p1, PointF p2, float z, byte precision = 4)
    {
        var slope = (p1.Y - p2.Y) / (p1.X - p2.X);
        var intercept = p1.Y - (slope * p1.X);
        var rawVal = slope * z + intercept;
        return (float)Math.Round(rawVal, precision);
        // using floats we end up with some infinitesimal rounding errors, 
        // so we need to set the precision to something reasonable. Default is 1/100th of a micron
        // I'm sure there's a better way than converting it to a string and then back to a float,
        // but that's what I've got right now, so that's what I'm doing.
        //var strVal = rawVal.ToString($"0.{precision}");
        //return float.Parse(strVal, CultureInfo.InvariantCulture);
    }*/
}