2x2 pixel format (lower resolution)

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2x2 pixel format (lower resolution)

(13 posts) (3 voices)

Started 2 years ago by oskob
Latest reply from patrickC

Tags:

OpenGL

oskob
Member

Hi!

I'm making a sort of old school game where I wanna use a lower resolution (half) than the iPhones screen to get that really primitive look so that each pixel is 2x2 pixels.

Right now I just scale up my images twice as big in the original file and add them to my stage with the original scale in cocos2d, but it feels as a waste of memory and cpu. Also, I have to move everything by 2 pixel steps which is kind of an ugly solution.

Is there a way to change the openGL matrix/ortho or whatever it's called (im pretty new to the whole openGL thing) so it draws the stage in double scale (no smoothing!) so I maybe get some extra performance out of the iphone (since it only have to render half as many pixels as my current solution) and more logical coordinates.

Thanks in advance!

Posted 2 years ago #
patrickC
Member
I would scale up the nodes/sprites in cocos2d, and make sure there is no antialiasing (default I think)
```
node.scale=2;
```
:)
Posted 2 years ago #
oskob
Member

Is it not possible to change the openGL projection instead? To me it sounds lake a waste of cpu to scale everything :/ And again, it would mess up the coordinates (x: 20, y:20 would really be x:10 y:10)

Posted 2 years ago #
patrickC
Member

Hm, well I don't know about it being a waste of cpu.
I believe when you scale it will change the drawing quad array and then just use that.
So it's not that at every draw call you're doing extra operations because of the scale.

Still, I see what you mean about moving everything by 2 pixels, but you could simply create a custom method to round up the coordinates of each drawn sprite before the draw call, so it does it "automatically" and you don't have to concern yourself with moving things by 2 pixel units.

If you want to do it purely by opengl I'm not sure of the path to take.
Have a look at the docs:
http://www.khronos.org/opengles/sdk/1.1/docs/man/
You could try a call to glScale (with the appropriate pushMatrix and popMatrix calls).

You could also take a look at some of the cocos2d scene transitions, in specific the zoomin/zoomout ones.

Hope that helps!

Posted 2 years ago #
oskob
Member

Ah, well if you don't think that it would make a performance boost it seems like scaling it and then making a method for handling the coordinates is less of a hustle.

One other thing though... If i wanna draw some primitives like diagonal lines and stuff, I guess is's gonna be a pain to draw 2x2 boxes of everything. I'm really a noob at OpenGL though so I guess im gonna have to live with that :)

Than you very much for your help!

Posted 2 years ago #
patrickC
Member
well you could always try with different line and point thickness if you're wanting to do that type of drawing with opengl, although not sure how "pixelated" the end result will look
```
glLineWidth(x);
glPointSize(x);
```
Posted 2 years ago #
riq
Key Master

If you scale the parent node (the Scene), then everything will be scaled, even the lines.
Also, the touches (coordinates) will handle the scaled nodes correctly.

Posted 2 years ago #
oskob
Member

Riq: ah that solved my coords problem, sweet!

Just like you say riq, the lines scales with the parent node (which is awesome :D) but I cant get them to look as blocky as I want. glPointSize(2.0f) doesn't seem to do anything at all :/

I use this to draw the line:

-(void)draw;
{
glDisable(GL_LINE_SMOOTH);
glPointSize(2.0f);
glLineWidth(4.0f);
glColor4ub(255,0,0,255);
ccDrawLine(_start, _end);
}

I searched around a little and found that GL_POINT_SIZE_MAX can limit this method and when I log the value its 0.
Is this a hardware limitation on the iPhone or can it be set somewhere?

Posted 2 years ago #
riq
Key Master

it's a hardware limitation. GL_POINT_SIZE_MAX is 1 on the device.

Posted 2 years ago #
oskob
Member

Aww.. Well, I guess I'll have to draw my own lines with ccDrawPoint or something. A big thanks to you both for your help!

Posted 2 years ago #
patrickC
Member
Hm, but I'm using the following code in a draw method with cocos2d-0.8.2
```
glLineWidth(4);
glColor4f(strapRed,strapGreen,strapBlue,1);
drawLine(_origin,_end);
```
and I get a line drawn with the correct thickness.
Are you seeing a 1px line or no line at all?
Posted 2 years ago #
oskob
Member

I'm seeing the line allright, but it's not "pixelated". It's drawn in the screens native resolution. glLineWidth works fine but I was hoping that glPointSize(2) could make the line draw in 2x2 squares

Posted 2 years ago #
patrickC
Member

Ah sorry I misunderstood.
Your best bet would be to fill an array with all your points and draw them in one call, similar to the ccDrawPoints function I think...
good luck ;)

Posted 2 years ago #

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