@ferdinand Thank you very much for your continuous help in the past two days. I just searched axis related content in cafe, and it is confirmed that my idea is wrong. You are a patient and good teacher. Thank you again, Ferdinand.:grin:

@ferdinand Hello ferdinand
thank you very much for the python matrix manual you provided me yesterday. I have solved this problem so far. However, there is a new problem. I hope that my axis can become vertical like the model, similar to the world coordinates. How to set my axis? Thank you

                const Vector xNor = xPos.GetNormalized();
		const Vector yNor = yPos.GetNormalized();
		const Vector zNor = zPos.GetNormalized();
		const Matrix m = Matrix(Vector(1,0,0),xNor, yNor, zNor);
		const Matrix inverseMat = ~m;

		op3->SetMg(inverseMat);


		const Matrix cuttomM = Matrix(Vector(1, 0, 0), Vector(0, 1, 0), Vector(0, 0, 1), Vector(0, 0, 0));

		//No response at this step
		op3->SetModelingAxis(cuttomM);
		
		ApplicationOutput(" m is @", inverseMat);

Hi Guys：
I'm sorry. Ferdinand told me that I should check the python matrix manual. After checking it, I thought that the python matrix was very easy to understand, but could not be applied to the c++ matrix, which made me very confused. I've been worrying about this problem for four days. I hope that I can set the matrix through two points and set my axis. Next, I use pictures to explain my problem. If I can provide the c++ code, Thank you very much (there may be some problems with the software translation I use. Please forgive me).
thx!

@ferdinand I think I understand. I'm trying to convert now. Thank you for your continuous answers

@ferdinand thx ferdinand,The example I wrote above is feasible in other software. Maybe Maxon has its own matrix method. I am looking for a way to implement this example through C4d c++. The matrix in the SDK gives me a headache. I need a 3*3 matrix
In addition, I found that my title was wrong, not "custom convert matrix to polygon", but "custom convert matrix to polygon". Thank you very much for helping me merge posts

Hi Guys：
I hope to get an inverse matrix through two points, and then give this matrix to my model. So far, I have got two "vectors (point postion)". I'm sorry, I'm a novice in c++ and I'm confused by multiple matrices. I hope to get good results like the example below. :disappointed_relieved: Thank you

v@my_y = normalize(@P-point(1,"P",0));
v@my_x = normalize(cross({0,1,0},v@my_y));
v@my_z = normalize(cross(v@my_x,v@my_y));

3@mm = set(v@my_x,v@my_y,v@my_z);

@P *= invert(m);

SetModelingAxis

Vector up = Vector(0,1,0);
Vector yPos = Normalize(point1Pos-point2Pos);
Vector xPos = Normalize(Cross(up,yPos));
Vector zPos = Normalize(Cross(xPos, yPos));

edited by @ferdinand:

@Neekoe said:

I want to customize my axis through this method, thx :face_with_cowboy_hat:

@m_magalhaes Thank you, I think I understand

@m_magalhaes Hi,m_magalhaes, I want to call your name again, because the last question is also your answer and has perfectly solved my problem. You are my God. Thank you very much.

Can I ask another question? Last night, I found that my tag name may be unclear. I want to use my own name. But gettagdata is not a member of baselist2d. I tried to browse the API, but I couldn't find the answer. For example, findcustomgui, which can be clearly known in the SDK, belongs to getdialog :disappointed_relieved:

@m_magalhaes
thank you so much,you and your code is perfact
:grin:

@m_magalhaes
Oh, no, I'm really excited. Thank you very much. I'm looking at my code in your way now
:grin: