Floating points images (pixel value in [0,1]) won't work properly with Volume visualization. The Grayvalue -> Opacity , Grayvalue/Gradient -> Opacity and Grayvalue->Color boxes shows no control points allowing for adjustment.
The result is barely tunable red 3D blob in the 3D window.
The issue was discovered when working with @s669m for visualization of CNN output data. The reason for this behaviour, as pointed out by @s434n, could be that MITK is unable to properly bin the pixel values for floating point data to create histogram. The hypothesis seems accurate- the same image when converted to int type works as expected in Volume Visualization view.