i want to make a 2d game and i'm stuck at time-independet collision detection. i read about "vector based collision detection" here:
Time-based logic / collision detection. it sounds like a good solution and i wrote this code:
bool Sprite::hasSpriteColl(Sprite *testObj)
{
Sprite *leftObj, *rightObj, *upperObj, *lowerObj;
// which is the left object and which the right?
if( this->posX < testObj->posX)
{
leftObj = this;
rightObj = testObj;
}
else
{
leftObj = testObj;
rightObj = this;
}
// which is the upper object and which the lower?
if( this->posY < testObj->posY)
{
upperObj = this;
lowerObj = testObj;
}
else
{
upperObj = testObj;
lowerObj = this;
}
// if the left object crosses the way of the right one and
// at the same time
// if the upper object crosses the way of the lower one
if( leftObj->posX + leftObj->width + leftObj->velX >= rightObj->posX + rightObj->velX &&
upperObj->posY + upperObj->height + upperObj->velY >= lowerObj->posY + lowerObj->velY)
return true;
else
return false;
}
i didn't test this code, but i noticed that it only works in one dimension. i drew the following image:
1, 2 and 3 are checked correct. 4 is also detected (both conditions are true), but 5 is wrong. the pass each other, but don't collide.
what have i forgetten or does someone have a good tutorial about vectorbased collision detection? i only need collision detection for rectangles, no circles, polygons or stuff like that.
