By means of the free videomemory element the current free videomemory can be detected that is available for textures (the value is expressed in bytes). This information can be used to decide, how many textures the program will use and what their quality will be like. For the OpenGL interface this information is not available. Therefore this function returns the substitution symbolic value of 4MB in the OpenGL interface. The texture is removed from the videomemory in case of initializing another interface or when deleting a picture containing the texture. It is therefore recommended to switch off the 3D window between the individual scenes (to set the size to 0) and to switch it on again (to restore the original size). A picture will be deleted, if all references to the picture are deleted, i.e. if the picture is not included in any variable. This can be reached by creating a unique picture copy, e.g. by modifying it by a double flipping over.