OpenGL interoperability's performance lose after cleaning-up

[takagi]

After cleaning-up, the performance of N-body example with OpenGL interoperability seems worse than that of before cleaning-up. If my memory is correct, OpenGL interoperability gave a little performance gain.

• before cleaning-up, about 5 percent of performance gain with OpenGL interoperability
• after cleaning-up, about 40 percent of performance lose with OpenGL interoperability

It is a disappointing result if OpenGL interoperability gives performance lose.

[takagi]

Close this issue because the difference of performance is caused by whether the rendered window is at most front, not by using OpenGL interoperability.