Matrix4d.shadow

Apply a projection transformation to this matrix that projects onto the plane specified via the general plane equation <code>x*a + y*b + z*c + d = 0</code> as if casting a shadow from a given light position/direction <code>light</code>. <p> If <code>light.w</code> is <code>0.0</code> the light is being treated as a directional light; if it is <code>1.0</code> it is a point light. <p> If <code>M</code> is <code>this</code> matrix and <code>S</code> the shadow matrix, then the new matrix will be <code>M * S</code>. So when transforming a vector <code>v</code> with the new matrix by using <code>M * S * v</code>, the shadow projection will be applied first! <p> Reference: <a href="ftp://ftp.sgi.com/opengl/contrib/blythe/advanced99/notes/node192.html">ftp.sgi.com</a>

@param light the light's vector @param a the x factor in the plane equation @param b the y factor in the plane equation @param c the z factor in the plane equation @param d the constant in the plane equation @return this