CSharpCAD vs OpenSCAD performance numbers.

[briansturgill]

I have a library I wrote for OpenSCAD called QBox (Quick Box).
It makes fancy custom boxes for Arduino/Raspberry Pi projects (with associated sensors, etc.).
I translated it from OpenSCAD to CSharpCAD, a full render (i.e. producing STL files):
OpenSCAD: 23.845 seconds
CSharpCAD: 2.002 seconds

JSCAD runs 2-4 times slower than CSCAD depending on what's being used, so a good estimate of how long it would take would be 4 seconds. How can OpenSCAD (written in C++) be so slow?

(Oh, the box below is for an intercom. The Arduino breadboard is glued to the bottom with 2 sided tape.
The top has a place for a speaker, microphone and button.
On the side is a BME-280 temperature/humidity/air pressure sensor.
The tall box in the center is upside down... i.e. the "bottom" is placed on what appears to be its top.

namespace QBoxExample; 

using CSharpCAD;
using static CSharpCAD.CSCAD;
using QBox;
using static QBox.QBoxUtils;
using static QBox.QBoxComponents;

static class Program
{
    static int segments = 50;
    static int fillet = 7;
    static double w = 120; // Inner box width (X)
    static double d = w / 1.618; // Inner box depth (Y)
    static double h = 65; // Inner box height (Z)


    static bool useMarkers = false; // Use markers instead of printing side wall items.

    static double spkHoleSpacing = 41;

    static QBox qb = new QBox(w, d, h, segments: segments, fillet: fillet);

    static Geometry Speaker()
    {
        return Union(
            Translate((0, 0, 0), TapPost(6, 3)),
            Translate((spkHoleSpacing, 0, 0), TapPost(6, 3)),
            Translate((0, spkHoleSpacing, 0), TapPost(6, 3)),
            Translate((spkHoleSpacing, spkHoleSpacing, 0), TapPost(6, 3))
        );
    }

    static Geometry SpeakerHoles()
    {
        var ctr = spkHoleSpacing / 2;
        return Translate((ctr, ctr, 0.01),
            CircularSpeakerGridHoles(20, 3));
    }

    static Geometry MakeBody()
    {
        return Subtract(
            Union(
                qb.SimpleBoxBody(true),
                !useMarkers ? qb.Left(d / 2, 2 * (h / 3), Bme280()) : new Geom3()
            ),
            qb.Right(d / 2, h - 15, HorizontalSlotHole(12, 7)), // Slot for micro-usb
            useMarkers ? qb.Left(d / 2, 2 * (h / 3), Bme280Marker()) : new Geom3(),
            qb.Left(d / 2, 2 * (h / 3), Bme280Hole())
        );
    }


    static Geometry MakeBottom()
    {
        var spk_off = (d - spkHoleSpacing) / 2;
        return Subtract(
            Union(
                qb.SimpleBoxBottom(),
                qb.Bottom(spk_off + 8, spk_off, Speaker()),
                qb.Bottom(w - 28, d / 3, Max9814Mic(rot: 90))
            ),
            qb.Bottom(spk_off + 8, spk_off, SpeakerHoles()),
            qb.Bottom(w - 28, 2 * (d / 3), Hole(6)), // 12mm d pushbutton
            qb.Bottom(w - 28, d / 3, Max9814MicHole())
        );
    }

    static Geometry MakeLid()
    {
        return qb.SimpleBoxLid();
    }

    static void Main(string[] args)
    {
        Save("/tmp/body.stl", MakeBody());
        Save("/tmp/lid.stl", MakeLid());
        Save("/tmp/bottom.stl", MakeBottom());
        var glue = Union(
            Translate((-10, -20, 0), Bme280()),
            qb.SimpleBoxPosts()
        );
        Save("/tmp/glue.stl", glue);
    }
}

[hrgdavor]

How can OpenSCAD (written in C++) be so slow?

OpenScad uses different engine I think for rendering that is faster for booleans (SDF Signed Distance Fields), but converting those to a mesh is a tricky thing to optimize for speed.