c# 绘制z轴

Question

I'm drawing coordinate axes in picturebox

    void draw_cor()
    {
        int w = pictureBox1.ClientSize.Width / 2;
        int h = pictureBox1.ClientSize.Height / 2;
        Refresh();
        Graphics e = pictureBox1.CreateGraphics();
        e.TranslateTransform(w, h);
        DrawXAxis(new Point(-w, 0), new Point(w, 0), e);
        DrawYAxis(new Point(0, h), new Point(0, -h), e);
        DrawZAxis(new Point(-pictureBox1.ClientSize.Width , pictureBox1.ClientSize.Height), new Point(pictureBox1.ClientSize.Width, -pictureBox1.ClientSize.Height ), e);

    }

markup and text for the x axis as an example

    private void DrawXAxis(Point start, Point end, Graphics g)
    {
        for (int i = Step; i < end.X; i += Step)
        {
            g.DrawLine(Pens.Black, i, -5, i, 5);
            DrawText(new Point(i, 5), (i / Step).ToString(), g, false);
        }

        for (int i = -Step; i > start.X; i -= Step)
        {
            g.DrawLine(Pens.Black, i, -5, i, 5);
            DrawText(new Point(i, 5), (i / Step).ToString(), g, false);
        }
        g.DrawLine(Pens.Black, start, end);
        g.DrawString("X", new Font(Font.FontFamily, 10, FontStyle.Bold), Brushes.Black, new Point(end.X - 15, end.Y));

    }

    private void DrawText(Point point, string text, Graphics g, bool isYAxis)
    {
        var f = new Font(Font.FontFamily, 6);
        var size = g.MeasureString(text, f);
        var pt = isYAxis
            ? new PointF(point.X + 1, point.Y - size.Height / 2)
            : new PointF(point.X - size.Width / 2, point.Y + 1);
        var rect = new RectangleF(pt, size);
        g.DrawString(text, f, Brushes.Black, rect);
    }

can someone explain how to make a method for marking the z axis? I understand that the shift should be diagonal in both x and y, but nothing worked out for me and no markup appears on the screen.(so far I have managed to draw only a straight line diagonally )

upd:

    private void DrawZAxis(Point start, Point end, Graphics g)
    {
        

        for (int i = -Step, j=Step ; i > start.X; i -= Step,j += Step)
        {
            g.DrawLine(Pens.Black, new Point(i-5, j), new Point(i+5, j));
           
            DrawText(new Point(i, j), (i / -Step).ToString(), g, false);
        }
...
}

I seem to have succeeded, but I ran into such a problem:

that is, the markup is not always on the coordinate axis. How to avoid this? It is necessary that the numbers are always on the axis (I suppose I should calculate the coefficient when the window is scaled, but only where to add it or by what to multiply?)

Answer 1

You are dealing with 3D data, so you should use 3D tools to transform your axes, and your data for that matter.

So you need to define a projection from 3D space to 2D space. This is usually done by defining a projection matrix. There are multiple projections to chose from, it looks like your projection is Oblique, but orthographic and perspective projections are also common. The System.Numerics.Vectors library has classes for Matrix4x4 , vector2/3/4, with methods to create your projection and transform your vectors.

After transforming a vector you can simply keep the x/y values and discard the z-value to get your image coordinates. Note that if using a perspective transform you need a vector4 and divide the x/y/z elements by W.

Armed with these tools it should be a fairly simple thing to generate start/end points for each axis, and create tick-marks in 3D, before projecting everything to 2D for drawing.

Another option would be to just do everything in Wpf3D to start with, this will likely make some functionality like rotating the camera simpler.