An application that uses C++ employs the the dvDirection member (a D3DVECTOR structure) of the D3DLIGHT7 structure. Direction vectors are described as distances from a logical origin, regardless of the light's position within a scene. Therefore, a spotlight that points straight into a scene (along the positive z-axis) would have a direction vector of <0,0,1> no matter where its position is defined to be. Similarly, you could simulate sunlight shining directly down on a scene by using a directional light whose direction is <0,-1,0>. Obviously, you don't have to create lights that shine along the coordinate axes; you can mix and match values to create lights that shine at more interesting angles.

Visual Basic applications set the light direction in the direction member of the light's D3DLIGHT7 type. The direction member is of type D3DVECTOR. Direction vectors are described as distances from a logical origin, regardless of the light's position within a scene. Therefore, a spotlight that points straight into a scene (along the positive z-axis) would have a direction vector of <0,0,1> no matter where its position is defined to be. Similarly, you could simulate sunlight shining directly down on a scene by using a directional light whose direction is <0,-1,0>. Obviously, you don't have to create lights that shine along the coordinate axes; you can mix and match values to create lights that shine at more interesting angles.