Movement goes Slow After a period of time - c++

Question

hello every body : a problem in the issue of Player movement.
I have a Player character in empty scene moves from point A to B and returns to A in constant speed , At first hour of game running it was OKAY , After three Hours the movement became slow and slow , thank beforehand
Game.h
D3DXMATRIX Player_Matrix ; //main player matrix .
D3DXVECTOR3 PlayerPos; //main player position .
D3DXVECTOR3 PlayerLook; //main player Look at position .
Game.cpp
//Initialize()
D3DXMatrixIdentity(&Player_Matrix);
PlayerPos = D3DXVECTOR3(10.0f,0.0f,10.0f);
PlayerLook = D3DXVECTOR3(0.0f,0.0f,1.0f);
.
//MovePlayer()
//declarations
static float angle = D3DXToRadian(0);
float Speed = 70.0f ;
PlayerPos += ( PlayerLook * ( Speed * (m_timeDelta)) );
if(PlayerPos.x >= 320) // 320:(B)
{
angle = D3DXToRadian(180);
}
if(PlayerPos.x <= 0) // 0:(A)
{
angle = D3DXToRadian(180);
}
//Setting up player matrixes
D3DXMATRIX TransMat , RotMat , TempMat , ;
D3DXMatrixIdentity(&TempMat);
D3DXMatrixIdentity(&RotMat);
D3DXMatrixIdentity(&TransMat);
//Setup Rotation matrix .
D3DXMatrixRotationY(&RotMat,angle);
angle = 0.0f ;
//Attach PlayerLook Vector to rotation matrix
D3DXVec3TransformCoord(&PlayerLook,&PlayerLook,&RotMat);
//gathering rotation matrix with player matrix
D3DXMatrixMultiply(&Player_Matrix,&Player_Matrix,&RotMat);
//transmat is an empty matrix to collect new player position
D3DXMatrixTranslation(&TransMat, PlayerPos.x,PlayerPos.y, PlayerPos.z);
//multiply new position matrix with main player matrix
D3DXMatrixMultiply(&TempMat,&Player_Matrix,&TransMat);
d3ddev->SetTransform(D3DTS_WORLD,&TempMat);
Main_Player->Render();

Answer 1

I would look into how you're calculating m_timeDelta. Perhaps your methodology is allowing floating point error to build up.
Here's an article on the subject: https://randomascii.wordpress.com/2012/02/13/dont-store-that-in-a-float/
I'm with Tom Forsyth, and think that 64-bit integer is the best storage type for absolute times (http://home.comcast.net/~tom_forsyth/blog.wiki.html#[[A%20matter%20of%20precision]]), but double will work fine too.

Answer 2

PlayerLook seems suspicious.
It is being iteratively rotated every frame, with floating point errors it's possible it might gradually be shrinking, probably only on the frames where the rotation changes.
You could confirm by looking at its value in the debugger after several hours of running, or you could eliminate it as a possibility if you renormalize it every frame and see if the slowdown disappears.

Answer 3

I've just found both the problem and its solution :
As I've explained before that all the App works fine , the problem is : the movement (just x++,y++,z++) gets slow and slow after a period of time . First I thought that it's a memory leak but the animation and delta time works fine .here, tried to find the reasonable problem that causes this .
I got the release of the App to other PC , after periods of time the App works fine , at that moment I saw the FPS won't reach 60.0 frame per sec , after search in MS DirectX SDK inside DXUT I found a struct which control FPS , there a Doc that speaks about GPU and the acceleration , they advice to control FPS and its limitation , Here is the Code :
//-----------------------------------------------------------------------------
// Name: LockFrameRate()
// Desc: Limit The frame Rate to specified
//-----------------------------------------------------------------------------
bool LockFrameRate(int frame_rate , float SecPerCnt )
{
static __int64 StartTime = 0 ;
__int64 CurTime = 0 ;
QueryPerformanceCounter((LARGE_INTEGER*)&CurTime);
float CurrentSecond = (float)((CurTime - StartTime )* SecPerCnt ) ;
// Get the elapsed time by subtracting the current time from the last time
// If the desired frame rate amount of seconds has passed -- return true (ie Blit())
if( CurrentSecond > (1.0f / frame_rate) )
{
// Reset the last time
StartTime = CurTime;
return true;
}
return false;
}
// int WINAPI WinMain(....)
//***************************
// Initialize Timing Preformance . *
//***************************
//Store Counts per second
__int64 CountPerSec = 0 ;
//Gets how many counts does the CPU do per second
QueryPerformanceFrequency((LARGE_INTEGER*)&CountPerSec);
//Gets second per count to preform it with different typs of CPUs
float SecondPerCount = 1.0f / CountPerSec ;
//Initial Previous Time
__int64 PrevTime = 0 ;
QueryPerformanceCounter((LARGE_INTEGER*)&PrevTime);
while(msg.message != WM_QUIT) // while not quit message , go on
{
if(PeekMessage(&msg,NULL,0U,0U,PM_REMOVE))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
else if(LockFrameRate(60 , SecondPerCount)) // If it is time to draw, do so , I selected 60 fps to limit
{
//Capture Current Time
__int64 CurTime = 0 ;
QueryPerformanceCounter((LARGE_INTEGER*)&CurTime);
//Calculate Delta Time
float DeltaTime =(float) ((CurTime - PrevTime) * SecondPerCount) ;
//Engine loop
Engine->Engine_Run(DeltaTime , SecondPerCount );
//After Frame Ends set Pervious Time to Current Time
PrevTime = CurTime ;
}
//else
//Sleep(1); // Give the OS a little bit of time to process other things
}
I commented Sleep(1) because I know scientifically it's just a burden on the CPU but I put it for Scientific confidence , that's between App and other there is a idle proc that waits for each other this is in nowadays computer technologies .
if you want to try it you can feel some screen stops happens these are unwanted
.
thank you Stack Over Flow .
. thank you guys .