Lookup functions to determine the orientation of cube map faces

[libs/gl.git] / source / texturecube.h

diff --git a/source/texturecube.h b/source/texturecube.h
index c8e18a11df59adfc123db32460999a5ad90acba8..0d23884f1458626b954f2a6badd871d38ff9026f 100644 (file)
--- a/source/texturecube.h
+++ b/source/texturecube.h
@@ -4,6 +4,7 @@
 #include "datatype.h"
 #include "pixelformat.h"
 #include "texture.h"
+#include "vector.h"
 
 namespace Msp {
 namespace GL {
@@ -21,8 +22,10 @@ enum TextureCubeFace
 /**
 Cube map texture, consisting of six square faces.  All of the faces must be of
 the same size.  A cube map texture is addressed by three-dimensional texture
-coordinates.  The face is first selected according to the largest coordinate,
-and the remaining two coordinates are used to sample the face image.
+coordinates, with a principal range of [-1, 1].  The face is first selected
+according to the largest coordinate, and the remaining two coordinates are used
+to sample the face image.  The images are oriented so that the cross product of
+the s and t axes will point into the cube.
 
 All faces of a cube map texture must be allocated for it to be usable.
 
@@ -35,6 +38,8 @@ private:
        unsigned size;
        unsigned allocated;
 
+       static Vector3 directions[6];
+
 public:
        TextureCube();
 
@@ -62,6 +67,23 @@ public:
        unsigned get_size() const { return size; }
 private:
        unsigned get_level_size(unsigned);
+
+public:
+       /** Translates indices into face constants.  Valid indices are between 0
+       and 5, inclusive. */
+       static TextureCubeFace enumerate_faces(unsigned);
+
+       /** Returns a vector pointing out of the face. */
+       static const Vector3 &get_face_direction(TextureCubeFace);
+
+       /** Returns a vector in the direction of the s axis of the face. */
+       static const Vector3 &get_s_direction(TextureCubeFace);
+
+       /** Returns a vector in the direction of the t axis of the face. */
+       static const Vector3 &get_t_direction(TextureCubeFace);
+
+       /** Returns a vector pointing to the center a texel. */
+       Vector3 get_texel_direction(TextureCubeFace, unsigned, unsigned);
 };
 
 } // namespace GL