[SOLVED] Physics bug? Objects are added to another world?

cocos2d-x C++
1

I’ve run into a small problem where for some reason bodies attached to one of my own Sprite classes seem to be added to a different world than the one my scene is using…

First, create a physics scene, (add a floor at the bottom if you want things to stay on screen).
World setup (in scene’s onEnter function):

auto physWorld = Director::getInstance()->getRunningScene()->getPhysicsWorld();
physWorld->setGravity(Vec2(0, -2200));
physWorld->setDebugDrawMask(PhysicsWorld::DEBUGDRAW_ALL);
physWorld->setSubsteps(3);

Add a key listener so you easily can spawn new objects, put this code in it.

if (key == EventKeyboard::KeyCode::KEY_SPACE)
	{
		auto org = Director::getInstance()->getVisibleOrigin();
		auto screen = Director::getInstance()->getVisibleSize();

		auto rad = 60.0f;
		auto circle = Node::create();
		auto circleBody = PhysicsBody::createCircle(rad);

		circle->addComponent(circleBody);
		circle->setPosition(RandomHelper::random_real(org.x + screen.width * 0.5, org.x + screen.width * 0.5 + 3), screen.height * 0.9);
		addChild(circle);

		auto c = Circle::init(RandomHelper::random_real(org.x + screen.width * 0.5, org.x + screen.width * 0.5 +3 ), screen.height * 0.9);
		auto cBody = PhysicsBody::createCircle(60);
		c->addComponent(cBody);
		addChild(c);
	}

Circle.h

#pragma once

#include "cocos2d.h"

using namespace cocos2d;

class Circle : public Sprite
{
		Circle();
		virtual ~Circle();

	public:
		static Circle* init(float x = 0, float y = 0);
};

Circle.cpp

#include "cocos2d.h"
#include "Circle.h"

Circle::Circle(void)
{
}

Circle::~Circle(void)
{
}

Circle* Circle::init(float x, float y)
{
	auto sprite = new Circle();

	if (sprite) {
		float cRadius = 60.0f;
		auto drawNode = DrawNode::create();
		drawNode->drawSolidCircle(Vec2(x, y), cRadius, 0, 8, 1, 1, Color4F::BLACK);
		sprite->addChild(drawNode);
		sprite->autorelease();
		return sprite;
	}

	CC_SAFE_DELETE(sprite);
	return sprite = nullptr;
}

The bodies attached to the Circle class objects does not collide with anything in the scene’s physics world, neither the floor or the other “node” circles, but it’s clear that there IS a body because they’re falling down… if you know what’s going on, please help.

2

You haven’t set any bitmasks…

cpp-tests has a working example. Plus I have released a few games with Physics.

3

Hm, when I saw your message I hoped it was the solution, but I tried it and it didn’t work. For your games, did you use the built-in stuff?

Also I’ve have

physWorld->setDebugDrawMask(PhysicsWorld::DEBUGDRAW_ALL);

and the outlines for the problematic bodies are not drawn (I’m assuming they should also have red outlines).
Guess I’ll take a look at the cpp-tests and hope that I can find a clue.

4

Problem solved! Here’s my Circle class as it should be:

Circle* Circle::init(float x, float y)
{
	auto sprite = new Circle();

	if (sprite) {

		sprite->setPosition(x,y);

		float cRadius = 60.0f;
		auto drawNode = DrawNode::create();
        // update! the vec2 is relative to the node's center point! 
        //setting it to x/y is (probably) not what you want.
		drawNode->drawSolidCircle(Vec2(0, 0), cRadius, 0, 8, 1, 1, Color4F::BLACK);
		sprite->addChild(drawNode);

		auto cBody = PhysicsBody::createCircle(60);
		sprite->setPhysicsBody(cBody);
		sprite->autorelease();
		return sprite;
	}

	CC_SAFE_DELETE(sprite);
	return sprite = nullptr;
}

So the reason I could see the drawnode but not the attatched body was b/c the body’s position was offset off-screen, or something like that.
Once again, the source of the problem was found between monitor and chair… :stuck_out_tongue:

1 Like
5

Yay, so glad. Have you read out docs about anchor point and position of Sprites? http://www.cocos2d-x.org/docs/cocos2d-x/en/sprites/manipulation.html

6

Oh yeah, I know about that, thanks.