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Sergio
Member
Hi,
I'd like to rotate sprite by X axis and set projection to center of app. And when I move sprite it simulate 3D view.
Is it possible to implement using cocos2d only(without openGL)?
If not, Coule you please provide very simple example how to do it using openGL.
Thank you.
If you are writing a game, use OpenGL ES and better still use Cocos2D which sits above OpenGL - sprites are rendered with this.
You need to look at some math stuff to do rotation. Go back to basics and look at unit circles to start with, then progress to how to rotate a point along the x/y axis.
x = r*cos(theta)
y = r*sin(theta)
If you use unit vector then you can remove r from the above equation.
Remember to work in Radians also and not degrees.
Sergio
Member
Steg90, Thank for reply. I appropriate it.
As I understand better to use cocos2d than OpenGL ES. Because it's wrapper under it and easy and faster to develop.
Actually I didn't understand how to 3D simulate using sprite.
Could you please explain in more details? I'm not strong in math.
Thanks.
Sergio,
Definitely use Cocos2D, it wraps around the OpenGL ES and then sprite rotations are simple, you can simply use one of Cocos2D sprite actions, for example:
[yourSprite runAction:[RotateTo actionWithDuration:0.1f angle:60]];
If you want to do true 3D, then look at OpenGL functions such as:
glVertex3fv, glMatrixMode, gluPerspective, gluLookAt, glTranslatef, glRotatef
to name a few.
NeHe has some good tutorials on OpenGL : http://nehe.gamedev.net/default.asp
This is a great site for OpenGL on iPhone : http://iphonedevelopment.blogspot.com/2009/05/opengl-es-from-ground-up-table-of.html
Good luck!
Sergio
Member
I've started to learn opengl es and want combine it with cocos.
So, I want to develop function for rotation by X axis:
CCSprite *sprite = [[CCSprite alloc] initWithFile:@"sprite.png"];
sprite.position = CGPointMake(0, 0);
[sprite setAnchorPoint:CGPointMake(0, 0)];
[self addChild:sprite];
glRotatef(50.0f, 0.0f, 1.0f, 0.0f);
CCSprite *sprite2 = [[CCSprite alloc] initWithFile:@"sprite.png"];
sprite2.position = CGPointMake(0, 300);
[sprite2 setAnchorPoint:CGPointMake(0, 0)];
[self addChild:sprite2];
glRotatef(0.0f, 0.0f, 1.0f, 0.0f );The problem is that it rotates all sprites(not first sprite only). I understand that it transform world matrix(not local related to sprite)
How to fix it?
Thanks.
GL rotations are always relative, so your last line has no effect.
What you want to do is either "un-rotate" everything:
glRotatef(50.0f, 0.0f, 1.0f, 0.0f);
...
...
glRotatef(-50.0f, 0.0f, 1.0f, 0.0f);or push and pop (save/restore) the opengl matrix as needed:
glPushMatrix();
glRotatef(50.0f, 0.0f, 1.0f, 0.0f);
...
...
//many other complicated opengl transformations as needed that would be annoying to backtrack on manually
...
glPopMatrix();
Sergio
Member
I tried as mentioned patrikC
// rotate first object by X axis
glRotatef(50.0f, 0.0f, 1.0f, 0.0f);
glPushMatrix();
CCSprite *sprite = [[CCSprite alloc] initWithFile:@"sprite.png"];
sprite.position = CGPointMake(0, 0);
[sprite setAnchorPoint:CGPointMake(0, 0)];
[self addChild:sprite];
glPopMatrix();
// rotate second object by Y axis
glRotatef(0.0f, 50.0f, 1.0f, 0.0f);
glPushMatrix();
CCSprite *sprite2 = [[CCSprite alloc] initWithFile:@"sprite.png"];
sprite2.position = CGPointMake(0, 300);
[sprite2 setAnchorPoint:CGPointMake(0, 0)];
[self addChild:sprite2];
glPopMatrix();But it don't work. It rotates all objects.(
Sergio
Member
No luck(
// rotate first object by X axis
glPushMatrix();
CCSprite *sprite = [[CCSprite alloc] initWithFile:@"sprite.png"];
sprite.position = CGPointMake(0, 0);
[sprite setAnchorPoint:CGPointMake(0, 0)];
[self addChild:sprite];
glRotatef(50.0f, 0.0f, 1.0f, 0.0f);
glPopMatrix();
// rotate second object by Y axis
glPushMatrix();
CCSprite *sprite2 = [[CCSprite alloc] initWithFile:@"sprite.png"];
sprite2.position = CGPointMake(0, 300);
[sprite2 setAnchorPoint:CGPointMake(0, 0)];
[self addChild:sprite2];
glRotatef(0.0f, 50.0f, 1.0f, 0.0f);
glPopMatrix();First you need create the sprite:
sprite = [[CCSprite alloc] initWithFile:@"sprite.png"];
sprite.position = CGPointMake(0, 0);
[sprite setAnchorPoint:CGPointMake(0, 0)];
[self addChild:sprite];in the loop:
glPushMatrix();
glRotatef(0.0f, 50.0f, 1.0f, 0.0f);
[sprite visit];
glPopMatrix();
Sergio
Member
No results.((
I need first sprite rotate by X axis. After this rotate second sprite by Y axis.
// rotate first object by X axis
CCSprite *sprite = [[CCSprite alloc] initWithFile:@"sprite.png"];
sprite.position = CGPointMake(300, 0);
[sprite setAnchorPoint:CGPointMake(0, 0)];
[self addChild:sprite];
glPushMatrix();
glRotatef(50.0f, 0.0f, 1.0f, 0.0f);
[sprite visit];
glPopMatrix();
// rotate second object by Y axis
CCSprite *sprite2 = [[CCSprite alloc] initWithFile:@"sprite.png"];
sprite2.position = CGPointMake(100, 100);
[sprite2 setAnchorPoint:CGPointMake(0, 0)];
[self addChild:sprite2];
glPushMatrix();
glRotatef(0.0f, 50.0f, 1.0f, 0.0f);
[sprite2 visit];
glPopMatrix();THank you
Shouldn't this:
glPushMatrix();
glRotatef(0.0f, 50.0f, 1.0f, 0.0f);
[sprite visit];
glPopMatrix();be in the draw call for that particular sprite?
Sergio
Member
I think did correct. Here you ara source code: http://slil.ru/29142628
There is "addSprite" function which is responsible for sprite adding and rotation.
Please review it. I appreciate you work.
Thank you.
robodude666
Member
Try the following:
-(void)draw
{
static float i = 0;
glPushMatrix();
glRotatef(i, 1.0f, 0.0f, 0.0f);
[sprite visit];
glPopMatrix();
glPushMatrix();
glRotatef(i, 0.0f, 1.0f, 0.0f);
[sprite2 visit];
glPopMatrix();
// angle x y z
if(i++ > 360) i = 0;
}
- (void)addSprites
{
CGSize s = [CCDirector sharedDirector].winSize;
// First Sprite will be rotated about the X-axis
sprite = [[CCSprite spriteWithFile:@"streak.png"] retain];
[sprite setColor:ccRED];
[sprite setPosition:ccp(s.width/2, s.height/2)];
// Second Sprite will be rotated about the Y-axis
sprite2 = [[CCSprite spriteWithFile:@"streak.png"] retain];
[sprite2 setColor:ccGREEN];
[sprite2 setPosition:ccp(s.width/2, s.height/2)];
}
-(void)dealloc
{
[sprite release];
[sprite2 release];
[super dealloc];
}You'll also have to add
CCSprite *sprite;
CCSprite *sprite2;as member variables of your class.
You can create your sprites as usual, except now that we're going to take control of them we have to do two things:
a) retain them so they are ours, which also means we need to release them in the dealloc
and
b) because we will be doing OpenGL modifications to them, we will not be adding them as a child.
If we were to add them as a child, we'd see two copies: The original one we added as a child that Cocos2D is controlling and the second copy from our own rotational modifications to the sprite. As we want to take control of the sprite manually, we will be drawing it via the visit method ourselves.
Last but not least we are doing all of the drawing in the draw method of our layer. This is the method that OpenGL will be active in. Doing OpenGL outside of the draw method is pointless as it won't have any affect, as you've seen.
In the demo above I simply rotate the two sprites, sprite and sprite2, in a circle about the X and Y axis respectively. They are both colored so you can easily see which is which.
Good luck!
-robodude666
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