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indy2005
Member
Hi,
When you are creating a Retina compatible game, how is Box2D affected? I am thinking in terms of the Pixels to Meters ratio which is normally used in Box2D applications. We don't use pixels we use points, and the PTM in theory could be twice the value on Retina over non Retina?
How does it work?
Regards
i
I personally do not change PTM_RATIO at all
With Retina display it's actually not a problem at all - points are points still, pixels don't matter. So no problem
iPad however, is a bit different as it introduces different screen size and ratio. When adding iPad support, I tend to leave the box2d world unaffected and modify the touches only. So my world stays at 480x320 but screen is 1024x768
JoeA
Member
Hello, when using the_debugDraw on retina I am seeing some strange things with my objects bodies. The objects seem to be the correct sizes, however, the world seems to be drawn on a standard display scale, all debug rects are drawn in the lower left hand corner.
It is like my x and y position are being scaled but the sizes are showing up correctly.
This is what I am doing:
b2BodyDef spriteBodyDef;
spriteBodyDef.type = b2_dynamicBody;
spriteBodyDef.position.Set(mainChar.position.x/PTM_RATIO, mainChar.position.y/PTM_RATIO);
spriteBodyDef.userData = mainChar;
b2Body *spriteBody = _world->CreateBody(&spriteBodyDef);
// Define another box shape for our dynamic body.
b2PolygonShape dynamicBox;
dynamicBox.SetAsBox(mainChar.contentSize.width/PTM_RATIO, mainChar.contentSize.height/PTM_RATIO);
//dynamicBox.SetAsBox([mainChar contentSize].width/2, [mainChar contentSize].height/2);//These are mid points for our 1m box
// Define the dynamic body fixture.
b2FixtureDef fixtureDef;
fixtureDef.shape = &dynamicBox;
fixtureDef.density = 1.0f;
fixtureDef.friction = 0.3f;
spriteBody->CreateFixture(&fixtureDef);I know something is not correct because my collisions in retina are not working property. Thank you for your suggestions in advance.
Joe
umm, no, no
It's the function SetAsBox that works a bit different than logic suggests
It does not create a box with width of X and height of Y. Instead it creates box which is 4 times larger (twice on each side), where X and Y are distances of the corners from the box's center
So if the center of the box is 0,0 then it's corners are (X,Y), (-X,Y) and so on. Thus the edges lenghts are 2*X and 2*Y, which makes the box twice bigger on each side than the contentsize of the sprite
vogueestylee
Member
hi, I have same problem, for example my ground is defined as:
// bottom
groundBox.SetAsEdge(b2Vec2(0,0), b2Vec2(screenSize.width/PTM_RATIO,0));
groundBody->CreateFixture(&groundBox,0);
// top
groundBox.SetAsEdge(b2Vec2(0,screenSize.height/PTM_RATIO), b2Vec2(screenSize.width/PTM_RATIO,screenSize.height/PTM_RATIO));
groundBody->CreateFixture(&groundBox,0);
// left
groundBox.SetAsEdge(b2Vec2(0,screenSize.height/PTM_RATIO), b2Vec2(0,0));
groundBody->CreateFixture(&groundBox,0);
// right
groundBox.SetAsEdge(b2Vec2(screenSize.width/PTM_RATIO,screenSize.height/PTM_RATIO), b2Vec2(screenSize.width/PTM_RATIO,0));
groundBody->CreateFixture(&groundBox,0);but when run this in drawdebug on retina display, it is 1/4 size.. what am I doing wrong?
edit: my beginning of code `CGSize screenSize = [CCDirector sharedDirector].winSize;
CCLOG(@"Screen width %0.2f screen height %0.2f",screenSize.width,screenSize.height);`
Heikki
Member
Thanks for your replies, guys :-)
Being a total Cocos2D newbie (and not knowing how to render the Box2D DrawDebugData to a separate layer), I went oldskool with a simple glScalef:
-(void) draw
{
// Default GL states: GL_TEXTURE_2D, GL_VERTEX_ARRAY, GL_COLOR_ARRAY, GL_TEXTURE_COORD_ARRAY
// Needed states: GL_VERTEX_ARRAY,
// Unneeded states: GL_TEXTURE_2D, GL_COLOR_ARRAY, GL_TEXTURE_COORD_ARRAY
glDisable(GL_TEXTURE_2D);
glDisableClientState(GL_COLOR_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glPushMatrix();
glScalef( CC_CONTENT_SCALE_FACTOR(), CC_CONTENT_SCALE_FACTOR(), 1.0f);
world->DrawDebugData();
glPopMatrix();
// restore default GL states
glEnable(GL_TEXTURE_2D);
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
}I also found Steffen Itterheim's Box2D helper class very useful:
http://cocos2d-central.com/page/index.html/_/retina-hd/proper-retina-content-scaling-with-box2d-r13
By replacing all the PTM_RATIO occurrences in your code with [Box2DHelper pixelsToMeterRatio], you can switch between Retina resolution and normal resolution without any problems.
haroon
Member
i am new to Box2d
My problem of collision is bit different images are ok in retina display but collision is not working properly.
Working fine on normal display, i am using Physics editor.
i am also using the helper class for content scaling, but not worked for me yet.
Thanks in Advance any suggestion will be helpful.
Thank you
Haroon
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