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# Question for Jiia: Mouse filtering

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This question is directed at Jiia, since it concerns his Collision Demo, but if anyone else has answers they would be appreciated. One of the things that really stood out to me in the demo is the smoothed mouse movement. Moving the mouse to look around gives a very smooth acceleration-based movement, rather than the typical precise jerky movement of the mouse. The camera doesn''t jump around, but rather glides from one angle to the next, giving a very professional feel. I''m assuming the demo uses mouse buffer filtering, possibly something similar to this on FlipCode, but even the demo provided there doesn''t have quite the same feel to it, its either too precise or lags behind the actual mouse movement too much. So, Jiia, if you''re there, how did you do it? How are you filtering the mouse while still keeping it responsive and accurate? Any tips (here or by email) would be greatly appreciated!

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The credit goes to PouyaCatnip and hplus0603 for explaining
weighted avarages to a total idiot such as myself.
See here

It's really simple. I defined two different ways of doing it
in my engine. They are:

Method 1: (used this for rotation in the demo)
A) Have a vector for the location you want the object.
B) Just do a weighted average each frame between that vector
and the current real vector to slowly get it there.

Method 2: (used this for movement in the demo)
A) Use velocities and force. The force is weighted into the
velocities each frame. The velocity is directly added to the
positions. This will speed it up smoothly.
B) Weight the Velocities against 0.0f after applying them
to the positions. This will slow the speed smoothly.

Here are some sections of code for method 2.
// "FDelay" is the time passed since last frame// WFactor = 0.995f in my demoFLOAT Factor = powf(WFactor, FDelay);if(Force.x) Velocity.x = (Velocity.x * Factor) + ((Velocity.x + Force.x) * (1.0f - Factor));if(Force.y) Velocity.y = (Velocity.y * Factor) + ((Velocity.y + Force.y) * (1.0f - Factor));if(Force.z) Velocity.z = (Velocity.z * Factor) + ((Velocity.z + Force.z) * (1.0f - Factor));// I then reset force to zero, because it is directly set each frame.// This slows it down (SFactor = 0.005f in my demo) I reversed// it because it made more sense as a "stopping" force.Velocity *= powf(1.0f - SFactor, FDelay);

Let me know if I need to clear something up

[edited by - Jiia on May 18, 2004 3:16:19 PM]

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This may also be something to fill some gaps:
// Update Camera AttributesVECTOR Move(0,0,0);if(KEYDOWN(DIK_W))	Move.z += 1.0f;if(KEYDOWN(DIK_S))	Move.z -= 1.0f;if(KEYDOWN(DIK_A))	Move.x -= 1.0f;if(KEYDOWN(DIK_D))	Move.x += 1.0f;D3DXVec3Normalize(&Move, &Move);Move *= 0.4f;// CamForward / CamRight are just direction vectorsCamera.Position.Force = (Move.z * Camera.CamForward) + (Move.x * Camera.CamRight);// Attempt is the vector "location I want to be at"Camera.Rotation.Attempt.x += MOUSE_MY * 0.005f;Camera.Rotation.Attempt.y += MOUSE_MX * 0.005f;// Oh yeah, then thisCamera.LookAt = Camera.Position.Current + Camera.CamForward;

[edited by - Jiia on May 18, 2004 3:30:35 PM]

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Awesome, thanks!! So it uses separate vectors for the mouse movement and camera angle, and uses weighted averages to move the camera angle towards the mouse angle. Damn, that is simple. And thanks for that other link, it sure does explain a lot!

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