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## 2d logical to view conversion

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### #1AlanSmithee  Members

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Posted 13 January 2014 - 09:22 AM

Hi.

I wanted to get some input from you guys on what method to use when converting logical positions and dimensions to their view counterparts and vice versa in a 2D game.

To give you some context, the game is a simple top down 2d game. The game is competitive and multiplayer. All game related positions and dimensions (x, y, widht, height etc) are in a logical cartesian space and when rendering it is scaled to view space. The other way around is also true, for example, when getting input from the mouse, the click position is converted from view to logical space.

Two psuedo code use cases might look like:

render(
camera.to_view(entity.x),
camera.to_view(entity.y),
camera.to_view(entity.w),
camera.to_view(entity.h)
);

get_mouse_pos(
camera.to_logical(mouse.x),
camera.to_logical(mouse.y)
);

So, I can think of two ways to do this.

1. Using a scale that depends on the level and screen width

scale.x = screenWidth / levelWidth;
scale.y = screenHeight / levelHeight;

This will make it so that the same number of logical units will be shown no mather what resolution the screen is. The logical positions and dimensions will simply be scaled to match the screen resolution.

pros

•
• gameplay will be the same on all screen resolutions (the same amount of logical units are always shown)
•

cons

•
• might look wierd on a lot of resolutions because of scaling
•

2. Using a fixed scale

scale = 10;

This will make it so that (screenWidth / scale and screenHeight / scale) number of logical units will be shown. The logical positions and dimensions are always scaled the same; by [scale] amount.

pros

• easier to make it look good, since scaling is always the same on all resolutions

cons

• will affect gameplay, since players using a screen with larger resolutions will see more of the level

PS: I say "screen" but you can think of it as a viewport, in case the game is no in fullscreen, everything still applies.

PSS: "positions and dimensions" are really points and vectors.. lol

So, I would love to get some feedback on what you think will work the best, thanks in advance! / AS

Edited by AlanSmithee, 13 January 2014 - 09:50 AM.

### #2richardurich  Members

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Posted 13 January 2014 - 09:46 AM

You should not distort the image to fit the screen. Someone can have 3 1080p monitors set up as 5760x1080, and you can probably imagine just how terrible the distortions would be. If you do go that route for any reason, at least let the user to pick 4:3 resolutions or whatever aspect ratio avoids distortions. If you want to see why, just look up reviews for games lacking that ability and read user comments.

You can also look at what other games do to solve your problems. Fog of war helps level the playing field if some people might see more of the map than others. Letting players zoom in and out also levels the playing field. Or you can just give some players an advantage, which a ton of games do.

### #3TheComet  Members

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Posted 13 January 2014 - 09:52 AM

Or

3. Using a scale that depends on level dimensions, screen dimensions, and aspect ratio:

float AR = screenWidth / screenHeight;
scale.y = screenHeight / levelHeight;
// Incorrect: scale.x = levelWidth * AR;
scale.x = scale.y * AR;

[EDIT] Fixed error pointed out below.

Edited by TheComet, 13 January 2014 - 10:46 AM.

"I would try to find halo source code by bungie best fps engine ever created, u see why call of duty loses speed due to its detail." -- GettingNifty

### #4AlanSmithee  Members

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Posted 13 January 2014 - 10:10 AM

Hey guys, thanks for the quick feedback.

You should not distort the image to fit the screen. Someone can have 3 1080p monitors set up as 5760x1080, and you can probably imagine just how terrible the distortions would be. If you do go that route for any reason, at least let the user to pick 4:3 resolutions or whatever aspect ratio avoids distortions. If you want to see why, just look up reviews for games lacking that ability and read user comments.

Yeah, thinking about it, it wouldn't make any sense to fit it to the screen.. I took a video game programming course once that had us do that, I think that is why it got stuck in my system.

You can also look at what other games do to solve your problems. Fog of war helps level the playing field if some people might see more of the map than others. Letting players zoom in and out also levels the playing field. Or you can just give some players an advantage, which a ton of games do.

This is quite funny, as my game features both FOV and zooming, so there is already a solution to the "problem" I am asking about.

Or

3. Using a scale that depends on level dimensions, screen dimensions, and aspect ratio:

float AR = screenWidth / screenHeight;
scale.y = screenHeight / levelHeight;
scale.x = levelWidth * AR;

Hmm could you please give me an example of that.. This is what I come up with, and it makes no sense.

float AR = screenWidth / screenHeight;
scale.y = screenHeight / levelHeight;
scale.x = levelWidth * AR;

screenWidth  = 640;
screenHeight = 480;
levelWidth   = 100;
levelHeight  = 100;
AR  = 1.33334;
scale.y = 4.8;
scale.x = 133.334;

screenWidth  = 1280;
screenHeight = 1048;
levelWidth   = 100;
levelHeight  = 100;
AR  = 1.22137;
scale.y = 10.48;
scale.x = 122.137;

screenWidth  = 1920;
screenHeight = 1080;
levelWidth   = 100;
levelHeight  = 100;
AR  = 1.77778;
scale.y = 10.80;
scale.x = 177.78;

I guess it is supposed to be:

scale.x = scale.y * AR?

Edited by AlanSmithee, 13 January 2014 - 10:22 AM.

### #5TheComet  Members

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Posted 13 January 2014 - 10:44 AM

I guess it is supposed to be:

scale.x = scale.y * AR?

Yes quite correct. Sorry, I was thinking too quickly.

"I would try to find halo source code by bungie best fps engine ever created, u see why call of duty loses speed due to its detail." -- GettingNifty

### #6AlanSmithee  Members

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Posted 13 January 2014 - 12:21 PM

OK

For now, I'm going to stick with using a fixed scale as that suites my needs the most, but using the aspect ratio will probably come in handy when I'm going to update the GUI.

Thanks a bunch to both of you.

Edited by AlanSmithee, 13 January 2014 - 12:29 PM.

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