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I am using .net-android and want to use canvas to draw cube and rotate it.this is the code:`public class XyCube
{
public float width;
public float height;
public Color Color;
public float center_x;
public float center_y;
public float center_z;
public float size;
public double speed;
public double line_width = 0;
Paint paint;
public XyCube(float w, float h, Paint _paint)
{
width = w;
height = h;
Color = Android.Graphics.Color.ParseColor("#ff000f");
center_x = width / 2;
center_y = height / 2;
center_z = 0;
size = height / 2 / 2;
speed = 30 / (float)180 * Math.PI;
line_width = Math.Min(width, height) / 150;
paint = _paint;
vertices[0, 0] = center_x - size;
vertices[0, 1] = center_y - size;
vertices[0, 2] = center_z - size;
vertices[1, 0] = center_x + size;
vertices[1, 1] = center_y - size;
vertices[1, 2] = center_z - size;
vertices[2, 0] = center_x + size;
vertices[2, 1] = center_y + size;
vertices[2, 2] = center_z - size;
vertices[3, 0] = center_x - size;
vertices[3, 1] = center_y + size;
vertices[3, 2] = center_z - size;
vertices[3 + 1, 0] = center_x - size;
vertices[3 + 1, 1] = center_y - size;
vertices[3 + 1, 2] = center_z + size;
vertices[5, 0] = center_x + size;
vertices[5, 1] = center_y - size;
vertices[5, 2] = center_z + size;
vertices[6, 0] = center_x + size;
vertices[6, 1] = center_y + size;
vertices[6, 2] = center_z + size;
vertices[7, 0] = center_x - size;
vertices[7, 1] = center_y + size;
vertices[7, 2] = center_z + size;
}
private int[,] edges = {
{ 0, 1 },{1,2},{2,3},{3,0},
{3+1,5 },{5,6},{6,7},{7,3+1},
{0,3+1 },{1,5},{2,6},{3,7}
};
private float[,] vertices = new float[8, 3];
private float[,] vertices1 = new float[8, 3];
private void DrawRect(Canvas canvas, float x1, float y1, float x2, float y2)
{
paint.SetStyle(Paint.Style.Fill);
paint.Color = Color;
canvas.DrawRect(x1, y1, x2, y2, paint);
}
public void DrawCube(Canvas canvas)
{
paint.SetStyle(Paint.Style.Stroke);
paint.Color = Color;
var ex = edges.GetLength(0);
float _x = float.MaxValue;
float _y = float.MaxValue;
for (int i = 0; i < ex; i++)
{
var x1 = vertices[edges[i, 0], 0];
var y1 = vertices[edges[i, 0], 1];
if (x1 < _x)
{
_x = x1;
}
if (y1 < _y)
{
_y = y1;
}
}
_x = center_x / 5 - _x;
_y = center_y / 5 - _y;
_x = 0;
_y = 0;
for (int i = 0; i < ex; i++)
{
//var x1 = vertices[edges[i, 0], 0];
//var y1 = vertices[edges[i, 0], 1];
//var x2 = vertices[edges[i, 1], 0];
//var y2 = vertices[edges[i, 1], 1];
var x1 = vertices1[edges[i, 0], 0];
var y1 = vertices1[edges[i, 0], 1];
var x2 = vertices1[edges[i, 1], 0];
var y2 = vertices1[edges[i, 1], 1];
canvas.DrawLine(x1 + _x, y1 + _y, x2 + _x, y2 + _y, paint);
}
}
public float[,] MultiplyMatrices(float[,] m1, float[,] m2)
{
float[,] res = new float[m1.GetLength(0), m2.GetLength(1)];
var row = m1.GetLength(0);
var cols = m2.GetLength(1);
for (int i = 0; i < row; i++)
{
for (int j = 0; j < cols; j++)
{
for (int x = 0; x < m2.GetLength(0); x++)
{
res[i, j] += m1[i, x] * m2[x, j];
}
}
}
return res;
}
public float[,] RotateVertex(float x, float y, float angle_x, float angle_y, float angle_z)
{
float[,] rotate_x =
{
{1,0,0 },
{0,(float)Math.Cos(angle_x), -(float)Math.Sin(angle_x)},
{0,(float)Math.Sin(angle_x),(float)Math.Cos(angle_x) }
};
float[,] rotate_y =
{
{(float)Math.Cos(angle_y),0,(float)Math.Sin(angle_y) },
{0,1,0 },
{-(float)Math.Sin(angle_y),0,(float)Math.Cos(angle_y) }
};
float[,] rotate_z =
{
{(float)Math.Cos(angle_z),-(float)Math.Sin(angle_z),0 },
{(float)Math.Sin(angle_z),(float)Math.Cos(angle_z),0 },
{0,0,1 }
};
//x -= center_x;
//y -= center_y;
float[,] rotateCube = new float[8, 3];
//float[]=MultiplyMatrices(rotate_x,)
for (int i = 0; i < 8; i++)
{
float[,] p = new float[3, 1]
{
{vertices[i,0] },
{vertices[i,1] },
{vertices[i,2] }
};
float[,] rx = MultiplyMatrices(rotate_x, p);
float[,] ry = MultiplyMatrices(rotate_y, rx);
float[,] rz = MultiplyMatrices(rotate_z, ry);
//rotateCube[i, 0] = rz[0, 0] + center_x;
//rotateCube[i, 1] = rz[1, 0] + center_y;
//rotateCube[i, 2] = rz[2, 0] + center_z;
rotateCube[i, 0] = rz[0, 0];
rotateCube[i, 1] = rz[1, 0];
rotateCube[i, 2] = rz[2, 0];
}
//vertices = rotateCube;
vertices1 = rotateCube;
return rotateCube;
}
```}private float angle_x = 0;
private float angle_y = 30 / (float)180 * (float)Math.PI;
private float angle_z = 0;public override bool OnTouchEvent(MotionEvent? e)
{
if (e == null)
{
return false;
}
var x = e.GetX();
var y = e.GetY();
if (mode == 0)
{
if (myCube == null)
{
return false;
}
if (e.Action == MotionEventActions.Down)
{
last_x = x;
last_y = y;
}
else if (e.Action == MotionEventActions.Move)
{
if (last_x > x + 5)
{
angle_x -= 3 / (float)180 * (float)Math.PI;
last_x = x;
}
else if (last_x + 5 < x)
{
angle_x += 3 / (float)180 * (float)Math.PI;
last_x = x;
}}}private XyCube? myCube;
{
paint.SetStyle(Paint.Style.Fill);
paint.StrokeWidth = 1;
for (int i = 0; i < Paths.Count; i++)
{
if (Paths[i].IsView)
{
paint.Color = Paths[i].Color;
canvas.DrawLine(Paths[i].X, Paths[i].Y, Paths[i].X1, Paths[i].Y1, paint);
}
}
if (mode == 0)
{
if (left_x > 0 && left_y > 0 && width > 0 && height > 0)
{
}
}
if (myCube == null)
{
myCube = new XyCube(canvas.Width, canvas.Height, paint);
}
myCube.DrawCube(canvas); ```}`what I want it rotate in original place but when I touch it it will rotate everywhere
your code looks suspect. if your rotating a cube, the vertex endpoints should be a vector of 3, (x,y,z) and the rotation should be in 3 angle directions. here is a simple javascript example:
https://www.instructables.com/Rotating-Cube-Using-JavaScript/
thank you this is what I want but is there irregular paths 3d? which means there is arc or other paths to 3d?
if you want to draw complex paths in 3d , you should switch to 3d package rather than using a 2d and transformations. with 2d you basically transform the vertices, but you really should apply transforms to each pixel.
you might look at OpenGL which android supports. apple has a deprecated OpenGl c library (they prefer you use Metal).
if you need cross platform, you could use a webkit canvas and a javascript library. see the popular:
Is there any library that can do what I want:
I use some (x,y)s to draw the 3d shape. and then I will rotate it. can I get the right (x,y)s then I can re-draw it? I enter (x,y)s and angle then I will get the right (x,y)?
is there any library ?
there is no one library. you might look at DiligentGraphic which is a common wrapper around various 3d libraries (as it is a C++ library you still need a c# wrapper).
https://github.com/DiligentGraphics/DiligentEngine
depending on your goal, you may find js and webview more than sufficient and is the easiest to implement.
note: flutter has better 3d graphic support than Maui.
thank you now I will try c++ in windows. can I do this using eigen or direct3d?