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Rotation Problem

General and Gameplay Programming Programming

Started by Medo Mex January 29, 2016 01:23 AM

3 comments, last by Nypyren 8 years, 2 months ago

Medo Mex

891

Author

January 29, 2016 01:23 AM

I have a vehicle and trying to rotate the vehicle gun to look at the player.

The gun rotate to look at the player as expected but after the vehicle itself rotate I get the gun looking at wrong direction.

How do I resolve that?

Here is how I get the final tank gun world matrix:


FinalWorldMatrix = VehicleWorldMatrix * GunWorldMatrix;

and here is how I rotate the gun to look at the player:


D3DXQUATERNION NewQuaternion;
D3DXQuaternionIdentity(&NewQuaternion);

D3DXVECTOR3 forwardVector = playerPosition - entityPosition;
D3DXVec3Normalize(&forwardVector, &forwardVector);

D3DXVECTOR3 forward(0.0f, 0.0f, 1.0f);
float dot = D3DXVec3Dot(&forward, &forwardVector);

if (abs(dot - (-1.0f)) < 0.000001f)
{
    D3DXQuaternionRotationAxis(&NewQuaternion, &D3DXVECTOR3(0.0f, 1.0f, 0.0f), 3.1415926535897932f);
} else if (abs(dot - (1.0f)) < 0.000001f) {
    D3DXQuaternionIdentity(&NewQuaternion);
} else {
    float rotationAngle = (float)acos(dot);
    D3DXVECTOR3 rotationAxis;
    axis = cross(forward, forwardVector);
    D3DXVec3Normalize(&axis, &axis);
    D3DXQuaternionRotationAxis(&NewQuaternion, &axis, rotationAngle);
}

SetRotation(Index, NewQuaternion); // <-- This line will set the rotation in GunWorldMatrix

Nypyren

12,313

January 29, 2016 01:45 AM

Since your gun orientation is relative to the vehicle, you need to make it compute its orientation based on the player's position from the vehicle's perspective.

Multiply playerPosition by the inverse of VehicleWorldMatrix before calculating forwardVector.

Medo Mex

891

Author

January 29, 2016 02:34 AM

@Nypyren: I tried to do the following but now the gun is looking at one direction most of the time:


D3DXMATRIX WorldMatrixInversed;
D3DXMatrixInverse(&WorldMatrixInversed, NULL, &VehicleWorldMatrix);
D3DXVec3TransformCoord(&playerPosition, &playerPosition, &WorldMatrixInversed);

D3DXVECTOR3 forwardVector = playerPosition - entityPosition;
// ...

Medo Mex

891

Author

February 01, 2016 02:34 AM

Same problem, any help?

Nypyren

12,313

February 01, 2016 04:54 AM

Hmm. entityPosition represents the vehicle's position, right? I think, since your playerPosition is now in the vehicle's space, you don't need to subtract entityPosition anymore:


D3DXVECTOR3 forwardVector = playerPosition;

Rotation Problem

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