setViewMatrix function

void setViewMatrix (Matrix4 viewMatrix, Vector3 cameraPosition, Vector3 cameraFocusPosition, Vector3 upDirection)

Constructs an OpenGL view matrix in viewMatrix. View transformation is the inverse of the model transformation. View matrix is commonly used to compute the camera location/orientation into the full model-view stack.

cameraPosition specifies the position of the camera. cameraFocusPosition specifies the position the camera is focused on. upDirection specifies the direction of the up vector (usually, +Y).

Implementation 

void setViewMatrix(Matrix4 viewMatrix, Vector3 cameraPosition,
    Vector3 cameraFocusPosition, Vector3 upDirection) {
  final Vector3 z = (cameraPosition - cameraFocusPosition)..normalize();
  final Vector3 x = upDirection.cross(z)..normalize();
  final Vector3 y = z.cross(x)..normalize();

  final double rotatedEyeX = -x.dot(cameraPosition);
  final double rotatedEyeY = -y.dot(cameraPosition);
  final double rotatedEyeZ = -z.dot(cameraPosition);

  viewMatrix.setValues(x[0], y[0], z[0], 0.0, x[1], y[1], z[1], 0.0, x[2], y[2],
      z[2], 0.0, rotatedEyeX, rotatedEyeY, rotatedEyeZ, 1.0);
}