2D Box Collisions - What am I doing wrong? (C++) - c++

Question

I'm trying to make a platformer game in C++ and I have made a vector of blocks,
and I simply loop through the vector and check for the collision individually:
//Pseudo code
class Block{
...int x
...int y
...int width
...int height
};
class Player{
int x
int y
int width
int height
int hsp //horizontal speed
int vsp //vertical speed
int facing //0 = no direction, -1 = left, 1 = right
...
void loop()
{
if(keyboard_pressed(key_left) { x-=hsp; facing = -1;}
if(keyboard_pressed(key_right) {x+=hsp; facing = 1;}
if(keyboard_pressed(key_up) {y-=vsp;}
if(keyboard_pressed(key_down) {y+=vsp;}
if(keyboard_released(key_left | key_right) {facing = 0;}
for(int i = 0; i < blocks.size(); i++)
{
Block b = blocks.at(i);
check_Collision(b);
}
}
};
As you can see, my player simply moves according to hsp and vsp. Simple enough.
The main portion of my question is in check_Collision(). First I check to see if the player
is on top of the block, and if he is, let him stay there.
Then I check if the player is at the sides of the block.
But for some reason there's a problem. For some reason when I go under the top of the block,
he stays at the top, but then he gets shifted to the left side.
I honestly don't know where to go with this.
The following code only checks for the top and the left side:
check_Collision(){
///////////////////////////////////
var myLeft, myRight, myTop, myBot;
var bLeft, bRight, bTop, bBot;
myLeft = x;
myRight = x + width;
myTop = y;
myBot = y + height;
/////////////////////
bLeft = b.x;
bRight = b.x + b.width;
bTop = b.y;
bBot = b.y + b.height;
//////////////////////////////////
//Check if we are at the top
if(myBot + vsp > bTop+1){
y = bTop - height;
}
//Check if we are at the sides
if(myBot > bTop+2){
if(myRight + hsp > bLeft)
{
x = bLeft - width;
}
}
}
If anyone can point me into some tutorial on 2D box collision that would be great.

Answer 1

The logic you're using doesn't make sense to me. It's not enough just to check that the player is under the block: don't you also need to make sure that the player is standing on it, ie, isn't too far to the right or left of the block? Similarly, in your second check, you've got to make sure that the player isn't jumping over the block (or standing on it). Your if partially checks this, but doesn't take into account the fact that the first check might have modified player position.
Can you assume that the player can't ever walk under the block? Can you assume that the player will never move fast enough to "tunnel" completely through the block (hsp > b.width, etc)?
If the answer to either of these is no, you will need significantly more sophisticated collision detection.