I just showed a sample of the output stream, not the whole stream. The IT command is used for independent axis moves. VT is used on vector moves on earlier controllers. For later Accelera controllers, VT has been removed and IT provides the smoothing for both independent and vector moves. That particular data stream came from a 2173 controller. VT is correct for it. This VT/IT parameter is a setting in the plugin. You can make the machine act how you want with it. The PID filters and VT/IT will smooth things out, or not. Your choice. I prefer to just run the profile as output by Mach. It's granular enough as to not make huge "stair steps". And besides, steppers use it all of the time. That is the output you get out of Mach. Mach sends data points, way points, dot plots, whatever you want to call them. They describe the movement. Mach does not send down CR, PR, or PA like information. In the Galil plugin, we take the incremental way point information from Mach and stuff them into a LI command (or CD command for contour mode).
As for your pictures, you will never get the first curve as output from Mach (input to the controller). There are no points to describe the spline! There is a time period between each point in the dot plot and this is a parameter that is settable by the plugin. This will determine the granularity of the system. If I tell Mach that I want way points on 1ms intervals, then the resulting dot plot is going to be really smooth to begin with. No smoothing required. Conversely, if I told Mach to output 32ms interval way point, then the dot plot it is going to be a lot rougher. A low granular system will benefit most from smoothing functions. However, it can't be as accurate.
With the smoothing functions, it may be possible to get the machine to move like the fist curve picture. But again, the points in each picture are the same! The data points simply do not adequately describe the curve in the first picture. If that plot is say 4ms between the points, then decreasing the time interval to 1ms is going to describe the curve with 4 times the data points and result in smoother motion.
This has nothing to do with closing the motion loop. It has everything to do with what kind of input the controller gets from Mach. If the controller is in LI mode, sending more LI commands with data points for the same move will yield a smoother profile. Generally, sending LI commands that represent 4ms of movement is sufficient. You get nice round circles with that. At least to the point where you really can't measure the faceting that all non linear moves have. 8ms is ok, but depending on the feed speed, faceting may be more than desired.
LI mode will "interpolate" between the points. How it does that depends on the other settings (IT or VT and VD/VA). Meaning, you can let the Galil motion profiler have some influence, if desired. Those VT, VD, VA values in that stream sample effectively turn the Galil profiler off. It is possible to smooth things too much and lose accuracy. It is also possible to "tune" the system to get awesome results. Leaving the default plugin parameters as they are yield very acceptable results. But tweaking them may yield better results depending on your machine.
CD mode will follow the dot plot precisely with no smoothing between the points. Accuracy is stellar. This is basically position over time, or PT. Like a stepper system. No "tuning" required (PID still needs to be tuned though!). This is the mode I would specify if the controller can do it and you have a fairly granular system as far as counts/unit and time interval is concerned and you don't want to play oscilloscope for hours on end searching for the "perfect" tune. I have run this mode on a highly rigid motion system (gear drive instead of belt on my Matsuura) with 2ms time slices and 12700 counts/inch and it is just plain awesome.
Which mode you use is up to the controller you have and/or your preference.
There is a new position and velocity over time (PVT) mode on the Accelera controllers that I will leverage for Mach4.
All of this is entirely dependent on the machine as a whole system. If you have a wet noodle sloppy motion system, you are not going to have good results no matter what features of the Galil you use.
If you still don't get it, then I would suggest getting a Galil and trying it out. The Galil is a high quality motion controller. The Acceleras are insanely fast (22MHz encoder inputs) which allows for insanely granular counts per unit on the encoders and still get high traverse speeds. In my opinion, pair a Galil with a good machine and Mach and NOTHING will be better. And it is the only motion controller that allows mixing of servos and steppers that I know of.
Steve