Fix compile error without SDL-image
Add auxiliary OpenGL method to bind texture
OnStep function returns result
Remove callback method for events
Define the class to render the scene
Split rendering procedure from scene class to the another class
Specify program before setting uniform value
Define renderer interface class
Define the class to render gradationally with OpenGL
Add uniformb setting methods
Redefine renderer class
Add the class to render ripples with OpenGL
Make ripple renderer attachable for stimulator
Define random stimulator