setFrustumMatrix function

void setFrustumMatrix (Matrix4 perspectiveMatrix, double left, double right, double bottom, double top, double near, double far)

Constructs an OpenGL perspective projection matrix in perspectiveMatrix.

left, right specify the coordinates for the left and right vertical clipping planes. bottom, top specify the coordinates for the bottom and top horizontal clipping planes. near, far specify the coordinates to the near and far depth clipping planes.

Implementation 

void setFrustumMatrix(Matrix4 perspectiveMatrix, double left, double right,
    double bottom, double top, double near, double far) {
  final double two_near = 2.0 * near;
  final double right_minus_left = right - left;
  final double top_minus_bottom = top - bottom;
  final double far_minus_near = far - near;
  perspectiveMatrix
    ..setZero()
    ..setEntry(0, 0, two_near / right_minus_left)
    ..setEntry(1, 1, two_near / top_minus_bottom)
    ..setEntry(0, 2, (right + left) / right_minus_left)
    ..setEntry(1, 2, (top + bottom) / top_minus_bottom)
    ..setEntry(2, 2, -(far + near) / far_minus_near)
    ..setEntry(3, 2, -1.0)
    ..setEntry(2, 3, -(two_near * far) / far_minus_near);
}