# How to limit movement in glOrtho2D to only show map

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How can I limit my movements when I scroll the window up/down/left/right to only show the tile map I have to render?

Say map is 640x640and viewport is 800x600?

Obviously 0, 0 is easy as that is the starting point and just test for if less than 0 but when try to move closer to the 640 width and height extent you have a -40 value...

Sorry if I am not coming off clear but I am dead tired right now... :(

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Well, you will need to define your map in terms of world units, since it is 2D I will assume world units are in pixels.

So if your tiles are 32x32 pixels you map will be, in pixels

20480x20480 pixels.

Assuming a zoom level of 1, so size of a world unit pixel is the same size as a screen pixel. This means your viewing volume is 800x600 pixels.

At this point you simply need to compare sides of your viewing volume to the sides of the map. For example, if the right side of the viewing space is greater than the map size, then the camera is outside the bounds. You then correct the bounds to match the mapSize

right = left + screenSize.width

if (right > mapSize.width)
{
// clamp the right side to the edge
right = mapSize.width
// since right = left + screenSize.width, I solve
// for the left based on the new right value
left = right - screenSize.width;
}

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Hmm I must be doing something wrong... I tried the code and not working...

It looks like it should make sense but I must be missing something.

I have my mouse in a buffer zone to scroll lthe view and I also use keys but neither way is working

int left = camera.getPositionX() + MOVE_AMT;
int right = left + SW;
//if(right > mapSize.width)
if(right > 640)
{
// clamp the right side to the edge
//right = mapSize.width
right = 640;
// since right = left + screenSize.width, I solve
// for the left based on the new right value
left = right - 800;
}

int x = 0, y = 0;
SDL_GetMouseState(&x, &y);
if(x > right)
return;
if(x > (SW - SCREEN_BUFFER_ZONE))
{
SDL_WarpMouseInWindow(MainWindow, SW, y);
camera.setPositionX(camera.getPositionX() + MOVE_AMT);
gameSprites.front()->setPositionX(gameSprites.front()->getPositionX() + MOVE_AMT);
}
else if(x < SCREEN_BUFFER_ZONE)
{
SDL_WarpMouseInWindow(MainWindow, 0, y);
camera.setPositionX(camera.getPositionX() - MOVE_AMT);
gameSprites.front()->setPositionX(gameSprites.front()->getPositionX() - MOVE_AMT);
}
else if(y >(SH - SCREEN_BUFFER_ZONE))
{
SDL_WarpMouseInWindow(MainWindow, x, SH);
camera.setPositionY(camera.getPositionY() - MOVE_AMT);
gameSprites.front()->setPositionY(gameSprites.front()->getPositionY() - MOVE_AMT);
}
else if(y < SCREEN_BUFFER_ZONE)
{
SDL_WarpMouseInWindow(MainWindow, x, 0);
camera.setPositionY(camera.getPositionY() + MOVE_AMT);
gameSprites.front()->setPositionY(gameSprites.front()->getPositionY() + MOVE_AMT);
}



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Well I got it working for the most part but when I change screen sizes e.g. from 800x600 to say 1920x1080 the width works fine still but the height movement is wrong...

It will not move in the one direction far enough, but stops fine for the opposite dir that heads to zero...

int x = 0, y = 0;
SDL_GetMouseState(&x, &y);
NX::ResourceManager* p = NX::ResourceManager::GetResourceManager();
NX::ResourceTMX* tmx = static_cast<NX::ResourceTMX*>(p->findResourcebyID(6));
const int OffsetHeight = abs(SH - tmx->getMap()->getMapHeightInPixels());
if(x > (SW - SCREEN_BUFFER_ZONE))
{
SDL_WarpMouseInWindow(MainWindow, SW, y);
if (camera.getPositionX() > SW - tmx->getMap()->getMapWidthInPixels() - SCREEN_BUFFER_ZONE)
return;
else
{
camera.setPositionX(camera.getPositionX() + MOVE_AMT);
camera.setPositionXDelta(camera.getPositionXDelta() + MOVE_AMT);
gameSprites.front()->setPositionX(gameSprites.front()->getPositionX() + MOVE_AMT);
}
}
else if(x < SCREEN_BUFFER_ZONE)
{
SDL_WarpMouseInWindow(MainWindow, 0, y);
if (camera.getPositionX() < SCREEN_BUFFER_ZONE)
return;
else
{
camera.setPositionX(camera.getPositionX() - MOVE_AMT);
camera.setPositionXDelta(camera.getPositionXDelta() - MOVE_AMT);
gameSprites.front()->setPositionX(gameSprites.front()->getPositionX() - MOVE_AMT);
}
}
else if(y > (SH - SCREEN_BUFFER_ZONE))
{
SDL_WarpMouseInWindow(MainWindow, x, SH);
if(camera.getPositionY() == 0)
return;
else
{
camera.setPositionY(camera.getPositionY() + MOVE_AMT);
camera.setPositionYDelta(camera.getPositionYDelta() + MOVE_AMT);
gameSprites.front()->setPositionY(gameSprites.front()->getPositionY() + MOVE_AMT);
}
}
else if(y < SCREEN_BUFFER_ZONE)
{
SDL_WarpMouseInWindow(MainWindow, x, 0);
if(camera.getPositionY() < (-OffsetHeight + SCREEN_BUFFER_ZONE))
return;
else
{
camera.setPositionY(camera.getPositionY() - MOVE_AMT);
camera.setPositionYDelta(camera.getPositionYDelta() - MOVE_AMT);
gameSprites.front()->setPositionY(gameSprites.front()->getPositionY() - MOVE_AMT);
}
}


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Anyone? I really can't get this to work... I have been at it for a few days now and just not able to understand why something so simple isn't working....  I can get one resolution to work, e.g. 800x600 but when I move to say 1024x768 or some other size that changes the size the logic falls apart.

Please provide a better example of the code I have posted or clean it up if you would!

thanks!

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