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Hi,
I've modified my game so scrolling works differently and the player stays in the center of the screen, now I'm having problems when jumping onto platforms, the player can land in the middle of them. Please take a look at screen shot:
I'm using Box2D and using a circle for the body. Do I need to do some checks to see if player is above platform or something? I've kinda tried this with PreSolve but to no affect.
Regards,
Steve
Trying to use PreSolve to check the player position and the platform position, if basically the player is below, then I want to disable the contact:
-(void) PreSolve:(b2Contact*) contact
{
b2Fixture* fixtureA = contact->GetFixtureA();
b2Fixture* fixtureB = contact->GetFixtureB();
if( (fixtureA == _platformFixture) || (fixtureB == _platformFixture))
{
return;
}
b2Vec2 position2 = b2Vec2(0,0);
float player_y_position = 0;
float platform_y_position = 0;
if(fixtureA == _playerFixture)
{
platform_y_position = fixtureA->GetBody()->GetPosition().y + 1;
player_y_position = fixtureB->GetBody()->GetPosition().y;
}
else {
player_y_position = fixtureB->GetBody()->GetPosition().y;
platform_y_position = fixtureA->GetBody()->GetPosition().y + 1;
}
b2Vec2 position = _playerFixture->GetBody()->GetPosition();
if (player_y_position < ( platform_y_position))
{
contact->SetEnabled(false);
}
}
But, it still seems to have been added to my contact listener and thus in my other bit of code:
std::vector<b2Body *>toDestroy;
std::vector<MyContact>::iterator pos;
for(pos = _contactListener->_contacts.begin(); pos != _contactListener->_contacts.end(); ++pos)
{
MyContact contact = *pos;
// See if player is on the ground (_platformFixture is actually the floor, lol )
if ((contact.fixtureA == _platformFixture && contact.fixtureB == _playerFixture) ||
(contact.fixtureA == _playerFixture && contact.fixtureB == _platformFixture))
{
bOnGround = true;
_bOnPlatform = false;
}
else // must be on a platform then
{
{
_bOnPlatform = true;
bOnGround = false;
}
}
} // end for
_bOnPlatform gets set to true when we hit any part of a platform - although the PreSolve should be disabling it?
Any ideas?
Thanks,
Steve
Please ignore my post above.
This is doing my head in now, this is my PreSolved method:
-(void) PreSolve:(b2Contact*) contact
{
b2Fixture* fixtureA = contact->GetFixtureA();
b2Fixture* fixtureB = contact->GetFixtureB();
if( fixtureA == _platformFixture && fixtureB == _playerFixture)
{
return;
}
else
{
if( fixtureA == _playerFixture && fixtureB == _platformFixture)
{
return;
}
}
float player_y_position = 0;
float platform_y_position = 0;
if(fixtureA == _playerFixture)
{
platform_y_position = fixtureB->GetBody()->GetPosition().y;
player_y_position = fixtureA->GetBody()->GetPosition().y;
}
else {
player_y_position = fixtureB->GetBody()->GetPosition().y; // player
platform_y_position = fixtureA->GetBody()->GetPosition().y; // platform
}
// NSLog(@"Player y pos:%f Platform y pos:%f", player_y_position, platform_y_position);
if (player_y_position < ( platform_y_position))
{
contact->SetEnabled(false);
}
}
I'm wondering why the contact even though it is getting disabled still causes a collision? Any ideas, I'm really getting to the end of my tether with this.
Regards,
Steve
Questor
Member
Steve,
Please make sure to wrap your code in ticks (or just highlight and select [code] in post menu)... it will help you to get more replies as the code will be alot more readable in the forums.
Not sure if I am missing something, but how is your contact->setEnabled(...) code ever going to get reached when you are doing this first?:
if( fixtureA == _platformFixture && fixtureB == _playerFixture)
{
return;
}
else
{
if( fixtureA == _playerFixture && fixtureB == _platformFixture)
{
return;
}
}I think this may be what you want for your PreSolve method (obviously I haven't tested this, but you get the idea):
-(void) PreSolve:(b2Contact*) contact
{
b2Fixture* fixtureA = contact->GetFixtureA();
b2Fixture* fixtureB = contact->GetFixtureB();
if ((fixtureA == _platformFixture && fixtureB == _playerFixture) ||
(fixtureA == _playerFixture && fixtureB == _platformFixture))
{
float player_y_position = 0;
float platform_y_position = 0;
if(fixtureA == _playerFixture)
{
platform_y_position = fixtureB->GetBody()->GetPosition().y;
player_y_position = fixtureA->GetBody()->GetPosition().y;
}
else {
player_y_position = fixtureB->GetBody()->GetPosition().y; // player
platform_y_position = fixtureA->GetBody()->GetPosition().y; // platform
}
// NSLog(@"Player y pos:%f Platform y pos:%f", player_y_position, platform_y_position);
if (player_y_position < ( platform_y_position))
{
contact->SetEnabled(false);
}
}
}Regards,
Q
Hi Questor,
Sorry about the code format, only just noticed the code tag.
Sorry for confusion with the code, the _platformFixture is in fact my ground, so I just return from the method if the collision is player with the ground.
I've messed around with it for ages and still can't get it to work. I'm thinking that it maybe the SetTransform I'm using to move the body of the player relative to the scrolling layer position?
I've also tried to detect when player walks into a block/box on the floor, just want to stop the scrolling horizontally if this happens, I thought Box2D did all this sort of stuff for you, i.e. not letting player walk through a body, but I guess if I'm scrolling the layer when player moves right, I need to stop scrolling it when player hits the box?
Regards and thanks for helping, I appreciate it.
Steve
Yes, the player :-)
The player is on the same layer that the platforms are on and hence the body definitions. The layer is scrolled horizontally and vertically thus I need to use SetTransform to keep the player body in the center of the screen.
I can't understand why this seems so difficult? If I continue to hold down the button that moves the player right for instance(ccTouchBegan), he will walk through the box's on the floor, but, if I keep 'clicking/touching' the button so to speak, he will stop when hit a box (I set a flag when player hits a box and do a check in the scrolling code if this flag is set, it doesn't scroll) - it is as though Box2D isn't stepping...
I'm kind of coming to the conclusion I'm doing it all the wrong way, but don't know any alternative way. I'm convinced if the screen wasn't scrolling and I moved the sprite around, collisions would work fine.
This is some code I also use to detect which bodies have collided, may give some more clues??
std::vector<b2Body *>toDestroy;
std::vector<MyContact>::iterator pos;
for(pos = _contactListener->_contacts.begin(); pos != _contactListener->_contacts.end(); ++pos)
{
MyContact contact = *pos;
// See if player is on the ground (_platformFixture is actually the floor, lol )
if ((contact.fixtureA == _platformFixture && contact.fixtureB == _playerFixture) ||
(contact.fixtureA == _playerFixture && contact.fixtureB == _platformFixture))
{
bOnGround = true;
_bOnPlatform = false;
}
else // must be on a platform as no other bodies in the world yet
{
_bOnPlatform = true;
bOnGround = false;
}
} // end forThis is the code I use to update the player sprite and body:
for(b2Body *b = world->GetBodyList(); b; b=b->GetNext())
{
if(b->GetUserData() != NULL) {
CCSprite *sprite = (CCSprite*)b->GetUserData();
switch(sprite.tag)
{
case kPlayerTag: // Player
{
CGPoint screenPos = [self position];
CGPoint temp = ccp(240 - screenPos.x, 160 - screenPos.y);
sprite.position = ccp(temp.x,temp.y);//* PTM_RATIO, temp.y * PTM_RATIO);
b2Vec2 b2Position = b2Vec2(temp.x/PTM_RATIO,
(/*-25+*/temp.y)/PTM_RATIO);
b->SetTransform(b2Position, 0); // Need to move body so always in centre of screen on x-coordinate
// NSLog(@"Body pos x:%f y:%f",b2Position.x*32, b2Position.y*32);
}
break;
}
}
else {
}
}and this to do the scrolling:
CGPoint screenposition = [self position];
if(Dir == Up)
{
if(_topJump <= _toJumpToLoc)
{
_topJump += 4;
screenposition.y -= 4;
}
else { // jumped done
Dir = Down;
}
}
else {
if(Dir == Down)
{
if(!bOnGround && !_bOnPlatform)
{
screenposition.y += 4;
}
}
}
CGPoint backLayerPos = [_backGroundLayer position];
backLayerPos.x += xVel / 6;
CGPoint newbackLayerPos = ccp(backLayerPos.x, backLayerPos.y);
[_backGroundLayer setPosition:newbackLayerPos];
screenposition.x += xVel;
[self setPosition:screenposition];Regards,
Steve
Questor
Member
Steve,
Looks like you got it resolved, per your post here: http://www.cocos2d-iphone.org/forum/topic/6445
Please try to make sure to update older threads rather than create new ones (or at least mention the issue is resolved in the old thread)... just so people don't bother trying to help you to debug something that is no longer an issue.
No offense intended, just a suggestion. Glad to see you got it all worked out.
Regards,
Q
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