i have been to this site to try and get my car movement sorted out. http://www.helixsoft.nl/articles/circle/sincos.htm

I have been having issues with it just moving the car in a circle because of the sin and cos that I have used I think I have done it correctly although the site does use fixed point number and I want to use floating point.

Here is my code

    if(myEngine->KeyHeld(Key_W))
    {
        length -= carSpeedIncrement;
    }
    if(myEngine->KeyHeld(Key_S))
    {
        length += carSpeedIncrement;
    }
    if(myEngine->KeyHeld(Key_A))
    {
        angle -= 0.01f;
    }
    if(myEngine->KeyHeld(Key_D))
    {
        angle += 0.01f;
    }

    carVolocityX = length * (sin(angle));
    carVolocityZ = length * (cos(angle));

    carPositionX += carVolocityX; 
    carPositionZ += carVolocityZ; 

    car[0]->MoveX((carPositionX * sin(angle)) * frameTime);
    car[0]->MoveZ((carPositionZ * cos(angle)) * frameTime);

I am open to new ideas on how to do this movement but it has to use vectors. Can anyoune see where I am going wrong with this.

Any help is appreciated.

• c++
• game-physics
• sin
• cos

Based on what you've said about MoveX and MoveZ, I think the problem is you're trying to pass an absolute position to a function which is expecting a velocity. Try

car[0]->MoveX(carVolocityX * frameTime);
car[0]->MoveZ(carVolocityZ * frameTime);

Why are you applying sin and cos both while calculating the velocity vector and while calculating a new position for your car?

Your code looks like you're trying to drive the car using the keyboard. If that's the case, try this

car[0]->MoveX((carPositionX) * frameTime);
car[0]->MoveZ((carPositionZ) * frameTime);

Note that I find it more clear to apply frameTime during the actual calculation of the distance and would suggest this edit:

carPositionX += carVolocityX * frameTime; 
carPositionZ += carVolocityZ * frameTime; 

car[0]->MoveX((carPositionX));
car[0]->MoveZ((carPositionZ));

If instead you just want to move it around in a circle, and not allow 'A' and 'D' to affect the angle,

car[0]->MoveX((carPositionX * sin(angularVelocity * totalTime)));
car[0]->MoveZ((carPositionZ * cos(angularVelocity * totalTime)));

You can use keys to adjust the (new) variable angularVelocity, or just assign a constant to see it working. The variable totalTime is the total time since the simulation began.