Question

I’m trying to calculate the point, which the Camera is looking on.
The Camera has a Rotation around the X-axis and the Y-axis.
I want to calculate the point, which is 1cm away and on the same line, as my Camera.

I know how to calculate something like this in 2D but when I get to 3D, I get in trouble.

This is for 2D (only x and z axis):

float c = 1f;
float a = c * Math.cos(Math.toRadians(rotationY));
float b = (Math.sin(Math.toRadians(rotationY)) * c);
newPosition.z -= a;
newPosition.x += b;

But with 3D I need help.

I hope somebody here knows the awnser.

Answer 1

One way would be to take the inverse of the camera’s view matrix, and then transform a point 1cm in front of the camera by this matrix.

If your camera first is rotated by X degrees around the X axis, and Y degrees around the y axis, then in pseudocode it might look like this:

Matrix4D camMM = Matrix4D.Identity(); //camera model matrix
camMM.Rotate(X, 1, 0, 0);
camMM.Rotate(Y, 0, 1, 0);
Vector4D focusPoint = camMM * vector4D(-1cm, 0, 0, 1);