This causes the model to behave oddly. The model lags behind where your camera is actually looking and the movement is jagged
Thats for you maybe, for me it works fine.
I assume that model is centered at origin and "pointing" in positive Z axis. Camera view matrix must be updated before you extract view matrix and use it for gun/hand final matrix.
Yeah, I see what you mean. It'll be easier to just draw the model in front of the camera.
Thanks for both of you , vinn your code is great I will try it and post a reply okay , belfegor I try it before and did not work for me :/ sorry , by the way thank you .
Q1 : How to show just the model hand and the gun ?
Q2 : How to make the town hands catch the gun (not just one !) , is that should be done in modeling software or I can make this as transformation matrices based on View matrices ....etc ?
One: You normally make a model of just the hands and the gun, then draw it in front of the screen or on a render target.
Two: You want the same model to hold and use multiple weapons? It'll probably be easier to just model the hands onto the guns, and animate it from there. So you will have to use some modeling software. Blender is free, if you don't have anything to use.
I use two models, one is the third person model; I only use it in multiplayer or for shadows. The second is the first person view. Which is just the arms and weapons.
Here is a debug photo to help you visualize how the model looks and how to draw it.