• Advertisement
Sign in to follow this  

Impulse resolution and position correction

This topic is 1420 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

**Please delete duplicate post in the maths section, realised I posted it incorrectly**

2D Platformer
Position correction and Impulse Resolution Issue:
Hello all. I am having some issues with my impulse resolution. So far I have an intersection test which returns whenever two AABB objects have collided. This works perfectly. 
Next, when the two objects have intersected, I need to do impulse resolution and then position correction to move the dynamic object in a certain manor. So far I have it working perfectly on the two sides:
The arrows indicate that the response works fine on these axis's.
Some code!
// ---- Calculating normals in x and y
float a, b, otherA, otherB;
a = max.y - min.y;
b = min.x - max.x;
otherA = other.max.y - other.min.y;
otherB = other.min.x - other.max.x;
float magnitude = sqrt(a*a) + (b* b); 
float magnitudeOther = sqrt(otherA * otherA) + (otherB * otherB); 
vector2D normal=(a/magnitude,b/magnitude); 
vector2D normalOther(otherA / magnitudeOther, otherB / magnitudeOther);
The first thing I do is calculate my normals which I use later on for my correction.
// ---- Masses so I can use inverse mass - hard coded for now
float m, mOther, inverse, inverseOther;
m = 50;
mOther = 50;
inverse = 1.f/m;
inverseOther = 1.f/mOther;
The next thing I do is calculate my extents:
vector2D extent, otherExtent;
	extent = min.add(max).scale(0.5f);
	otherExtent = other.min.add(other.max).scale(0.5f);

	float e = 0.6;
	float slop = 0.01;
	float percentage = 0.1;

From here I now work out my impulse resolution and position correction:
vector2D correction, pd, j;	

pd.x = (extent.x + otherExtent.x) - (other.getPosition().x - getPosition().x); // penetration in X - need to double check this
pd.y = (extent.y + otherExtent.y) - (other.getPosition().y - getPosition().y); // penetration in Y

correction.y = (std::max(pd.x-slop,0.00f) / (inverse + inverseOther))* percentage * normal.x; //  correction based on the max of pen - by the slop. Percentage for overlap
correction.y = (std::max(pd.y-slop,0.00f) / (inverse + inverseOther))* percentage * normal.y;
j.x = -(1.f + e) + (minus(other.vel).dotProduct(normal)) / inverse + inverseOther;
j.y = -(1.f + e) + (minus(other.vel).dotProduct(normal)) / inverse + inverseOther;

From here I apply the code to my velocity in Y using j.y + correction.y, this in turn results my dynamic object resting on my static object with a little bit of bounce, which is wrong. It needs to be resting there perfectly so allow clean movement. Little stuck on what to do next.

Share this post

Link to post
Share on other sites
Sign in to follow this  

  • Advertisement