I have a laptop with Nvidia Optimus technology, and I made the observation that whereas the Vanilla launcher launches the game in a way that makes the dedicated adapter kick in automatically, the FTB launcher does not seem to communicate the 3D nature of the launched process well enough. It required me to manually add "javaw.exe" to the 3D panel.
But then it worked and it should work. If not so, the driver isn't doing its job which seems to indicate the existence of either a human error or an obstructing process.
Here's a small check list of things to test:
- If using Optifine + multi-core chunk loading, is "Threaded optimization" disabled in the Nvidia settings for "javaw.exe"?
- Are you sure you added the correct "javaw.exe"? There may be more than one Java installed, check out the active one in the Java control panel applet.
- Make sure the launcher actually starts up 'javaw.exe'. If not so, add the corrisponding "java.exe" to the Nvidia applet as well.
- Almost all laptop manufacturers stuff their machines full of bloatware; make sure your manufacturer did not add some kind of "utility" that messes with/overrides graphics cards and adapter settings, and if they did, disable this utility.
- If none of the above helps, check your laptop's BIOS. There is a chance you may disable the integrated adapter from there.
In any case, google the exact brand of your laptop adding first the search term "+Nvidia", then "+minecraft +FTB". This way you will see if other users already found a generic response to the issue.