C# XNA 矩阵 - 找出矩阵乘法后的当前位置

Question

i am making 3D Simulation of Solar System

for every planet i have an instance of class Celestial Body . I am using the following code for revolution and rotation of sun, planets & their moons.

world = Matrix.CreateTranslation(0,0,0) * Matrix.CreateRotationY(rotation) * Matrix.CreateTranslation(position) * Matrix.CreateRotationY(revolution); 

• rotation is my float variable for rotation of planet around its own axis
• revolution is my float variable for revolution of planet in orbit
• position is to my vector3 variable to put the body in orbit or at its radius from center eg postion = new Vector3(70,0,0)

Now it works really fine.

But the problem is i need to locate \ get the position of my planet, to where it has been translated after the Matrix multiplication literally in x,y,x co-ordinates.

How To? get the current X, Y, Z coordinates of my planet

the other option for me would be to use some maths formula that calculates a 2D circle for me.

Answer 1

I think what you're looking for is Matrix.Translation . This gives you the x, y, z co-odinates of the matrix that it's called on in a Vector3 .

So, to get the new position, you should use

Vector3 newPosition = world.Translation;

after your calculations.