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When moving object around it moves smoothly but with jaggies and refresh artifiacts

Started by utilae Feb 22, 2008 at 1:04 AM 5 replies 2.7k views

Original Post

Feb 22, 2008 at 1:04 AM

Hi, I am using C++ and Direct3D9. When I move an object around on the screen at speed, I get the jaggies and refresh artifacts (possible blurring). Putting Vertical Sync on fixes this and makes it smooth, but everything is slow and the mouse movement is 'late' in terms of where you direct it. So V_Sync is not an option. I am working on a laptop with a good graphics card. The refresh rate is at 60Hz and I notice that when I move a notepad window around in windows xp sp2 it also does the same thing. But when playing games, ie guild wars, its perfect, no jaggies etc. So is this common for laptops? Would all games made for laptops do this. Or is there some way to cater for those on laptops. Edit: ok Guild Wars is using wait for vertical sync, but it is not as slow as my program when my program uses vertical sync. Help?

JohnBolton

Feb 22, 2008 at 1:17 AM

What you are experiencing is called "tearing". It is unavoidable if you are not synching with vertical retrace.

I'm not sure why everything slows down when you turn on vsync. Are you moving things a fixed distance per frame or a fixed distance per second? When you turn on vsync, you may be slowing down the frame rate (to match the refresh rate) and if you are moving a fixed amount per frame that will also slow down movement. In that case, your movement should be based on time instead.

utilae

Feb 22, 2008 at 2:01 AM

Yeah, I have implemented what I think is a time based game loop, but I don't know if it is working properly. I am pretty sure I have the interpolation part working. The main point of issue is the ticks per second and max frame skip. I'm not sure what those two are. I guess the ticks per second is the frames per second, cause if i set it to 60 or 120 I can move the mouse faster with vertical sync but it still is slow.

The game loop is based on this article:
http://dewitters.koonsolo.com/gameloop.html
"Fixed Update and Variable Rendering"

//message pumpMSG msg;//start game with the Game_Core gamestateif(Game_Core_Load()==false) return(0);//set game state pointers to initial game statessCurrentGameState="Game_Core";fnptrCurrentUpdateGameState=Game_Core_Update;fnptrCurrentRenderGameState=Game_Core_Render;//frame rate indepenent game loop variablesconst int nTICKS_PER_SECOND=25;const int nSKIP_TICKS=1000 / nTICKS_PER_SECOND;const int nMAX_FRAMESKIP=5;DWORD dwNextGameTick=timeGetTime();int nLoops=0;float fInterpolation=0;//GAME LOOPwhile(true)	{	//PEEK MESSAGE	//look for a message	if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))//there is a message	{		if(msg.message==WM_QUIT) break;//quit if that is the message		TranslateMessage(&msg);//translate message		DispatchMessage(&msg);//dispatch message	}		//FRAME RATE INDEPENDENT GAME LOOP	//fixed update        nLoops=0;        while(timeGetTime() > dwNextGameTick && nLoops < nMAX_FRAMESKIP)         {		//current update gamestate		fnptrCurrentUpdateGameState();	                dwNextGameTick += nSKIP_TICKS;                nLoops++;        }        //need other while loops for different updates at different speeds		        //variable render        fInterpolation=float(timeGetTime() + nSKIP_TICKS - dwNextGameTick) / float(nSKIP_TICKS);	fnptrCurrentRenderGameState(fInterpolation);//current render gamestate}Game_Core_Unload();//clean up program datareturn(msg.wParam);//return the wparam from the WM_QUIT message

ViperG

Feb 22, 2008 at 2:07 AM

what are you using to capture mouse movement?

the tearing can sometimes be solved by lowering fps down to around 60, but it depends on the monitor as well. All computers do this, v sync is the only way to fix it, but that usually puts fps max at 60.

utilae

Feb 22, 2008 at 2:19 AM

Activating Vertical Sync defintatly removes the tearing. But the problem I guess is that it makes the mouse and other things go slow. Most notably the mouse, since upon moving it really fast, it is 'late' and gets to its destination slower then it would in windows or without vertical sync.

In my game loop, by putting the const int nTICKS_PER_SECOND=60; or =120; the mouse moves faster, but it still slower then I would like. In guild wars, with vertical sync on the mouse seems to move as it should, really fast and really responsive.

For mouse movement I hide the mouse cursor and use an image (D3DXSprite) in its place. So I can set my own mouse icons.

In the windows procedure I do this:

                case WM_MOUSEMOVE:		{			//mouse has moved			GUIManager.m_pMouse->UpdateCurrentPos();		}break;		case WM_LBUTTONDOWN:		{			//left button is down			GUIManager.m_pMouse->SetMouseState(1);		}break;		case WM_LBUTTONUP:		{			//left button is up			GUIManager.m_pMouse->SetMouseState(2);			}break;		case WM_RBUTTONDOWN:		{			//right button is down			GUIManager.m_pMouse->SetMouseState(3);		}break;		case WM_RBUTTONUP:		{			//right button is up			GUIManager.m_pMouse->SetMouseState(4);		}break;

In the GUIManager.m_pMouse->UpdateCurrentPos() function the code is basically this:

//get mouse position on screenPOINT ptMousePos;GetCursorPos(&ptMousePos);//calculate current mouse positionm_ptCurrentMousePos.x=ptMousePos.x-16+m_ptHotSpot.x;m_ptCurrentMousePos.y=ptMousePos.y-16+m_ptHotSpot.y;//update screen rect positionm_recPos.top=ptMousePos.y-16;m_recPos.left=ptMousePos.x-16;m_recPos.right=m_recPos.left+32;m_recPos.bottom=m_recPos.top+32;

ViperG

Feb 22, 2008 at 2:30 AM

the problem is using WM_MOUSEMOVE:

Don't call your function in that, just take it out of that case statement and call it every frame (doesn't matter where you place it really).

windows messages are known for being slow.

and if you wan't to increase your click speed (usually this isn't an issue on windows messages, but just in case)

use

GetAsyncKeyState(VK_LBUTTON) etc

doesn't capture mouse wheel movements :(

going to need to use case WM_MOUSEWHEEL:

unless you switch completely over to directx input.

ALSO:

change your
if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))//there is a message

too:

while (PeekMessage(&msg,NULL,0,0,PM_REMOVE))//there is a message

reason:
windows can send more than 1 message at a time to your application during a update in your game loop, using if, you can only update 1 message at a time.
using while will process all available messages during a loop.

utilae

Feb 22, 2008 at 3:06 AM

Ok, so I took the update mouse function out of teh WM_MOUSEMOVE case and put it in the GUI update loop. Now (with VSync) when I put the game loop ticks per second at 120, the mouse goes blazing fast, which is excellent, so thats that problem solved.

EDIT: Ok, thank you. Problem sorted.

[Edited by - utilae on February 23, 2008 3:06:02 AM]

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