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[theman515]

I'm rolling my own physics system for my game and I piled all of my game objects into a list.

I'm using the boost::shared_ptr for each object and use a BOX struct for my bounding box, the getLeft() and getRight() etc, is to get the x co-ordinate and the x co-ordinate+ the width.

to move the characters i use a force vector and edit it using the setForceX and setForceY etc

here's my code:

Code:

void P_System::update()
{
    Iterator bumper;
    for(m_lListIt = m_lList->begin(); m_lListIt != m_lList->end(); m_lListIt++)
    {
        for(bumper = m_lList->begin();bumper!=m_lList->end();bumper++)
        {
            //if it hits the top or bottom
            if((m_lListIt->get()->getLeft() <= bumper->get()->getRight() && m_lListIt->get()->getRight() >= bumper->get()->getLeft()) && (m_lListIt->get()->getDown() <= bumper->get()->getUp() || m_lListIt->get()->getUp() >= bumper->get()->getDown()))
            {
                cout << 1;
                m_lListIt->get()->setForceY(0);
                bumper->get()->setForceY(0);
            }
            if((m_lListIt->get()->getLeft() <= bumper->get()->getRight() || m_lListIt->get()->getRight() >= bumper->get()->getLeft()) && (m_lListIt->get()->getDown() <= bumper->get()->getUp() && m_lListIt->get()->getUp() >= bumper->get()->getDown()))
            {
                m_lListIt->get()->setForceX(0);
                bumper->get()->setForceX(0);
            }

        }
    }
    for(m_lListIt = m_lList->begin(); m_lListIt != m_lList->end(); m_lListIt++)
    {
        m_lListIt->get()->setPosition(m_lListIt->get()->getX()+m_lListIt->get()->getForceX(),m_lListIt->get()->getY()+m_lListIt->get()->getForceY());
    }
}

what am i doing wrong? thanks in advance  

[SFBTom]

What's going wrong with the code? What are the symptoms?

[bateleur]

I find this style fairly unreadable, but as far as I can see this:

Code:

if((m_lListIt->get()->getLeft() <= bumper->get()->getRight() && m_lListIt->get()->getRight() >= bumper->get()->getLeft()) && (m_lListIt->get()->getDown() <= bumper->get()->getUp() || m_lListIt->get()->getUp() >= bumper->get()->getDown()))

...says this (in pseudocode)...

Code:

if (m.left() < b.right && m.right > b.left && (m.down() < b.up() || m.up() > b.down))

...which checks that the character overlaps the buffer horizontally and then checks that either it's bottom edge is below the top of the buffer or its top edge is above the bottom of the buffer. However, that might not be a collision at all.

Consider, for example, the case where the character is a long way directly above the buffer. His top edge is way above the bottom of the buffer, so the expression will evaluate to true. This doesn't seem to be what you want, because no collision has occurred.

[sorceress]

What can sometimes be helpful in logic is to look at the opposite problem: under what conditions will the character not collide with the object?

if the four corners of the character's bounding box are to the left of the object.
if the four corners of the character's bounding box are to the right of the object.
if the four corners of the character's bounding box are above the object.
if the four corners of the character's bounding box are below the object.

[rivon]

I would look at SDL_collide - just rewrite the int SDL_CollideBoundingBox(SDL_Rect a , SDL_Rect b) method.

[st33d]

What can sometimes be helpful in logic is to look at the opposite problem: under what conditions will the character not collide with the object?

if the four corners of the character's bounding box are to the left of the object.
if the four corners of the character's bounding box are to the right of the object.
if the four corners of the character's bounding box are above the object.
if the four corners of the character's bounding box are below the object.

But don't write it that way. Calculating the ! for a positive collision costs time in some languages.

[Mikademus]

I find this style fairly unreadable

Second this. The denser the code the harder it is to spot errors. If for no other reason, add descriptive variables for the benefit of the readers you're asking for help. Doing that might also give away the error while you're doing it.