0030476: Visualization, Path Tracing - Adaptive Screen Sampling leads to unstable...

0030476: Visualization, Path Tracing - Adaptive Screen Sampling leads to unstable results

OpenGl_View::runPathtrace() has been extended with alternative multi-pass
Adaptive Screen Sampling mode, not relying on atomic floating point operations.
Although atomic operations on floats allows single-pass rendering,
such operations leads to instability in case of different calculation order.
Atomic float operations are also currently supported only by single GPU vendor.

Fixed GLSL compilation on Intel drivers (follow ARB_shader_image_load_store
specs rather than EXT_shader_image_load_store).

Graphic3d_RenderingParams::AdaptiveScreenSamplingAtomic option has been added
to activate 1-pass Adaptive Screen Sampling mode when supported by hardware.

vfps command has been extended with -duration argument allowing to limit command execution time.
vactivate command has been extended with -noUpdate argument.