#extension GL_EXT_gpu_shader4 : enable // need GLSL v1.30 -> if not available, use a uniform for passing textureSize instead of calling textureSize2D
//#extension GL_EXT_gpu_shader4 : enable // need GLSL v1.30 -> if not available, use a uniform for passing textureSize instead of calling textureSize2D
#extension GL_EXT_gpu_shader4 : enable // need GLSL v1.30 -> if not available, use a uniform for passing textureSize instead of calling textureSize2D
//#extension GL_EXT_gpu_shader4 : enable // need GLSL v1.30 -> if not available, use a uniform for passing textureSize instead of calling textureSize2D