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A small 2D physics engine

Home Page: http://box2d.org/

License: MIT License

CMake 3.14% C 6.04% C++ 89.68% Shell 0.56% Batchfile 0.59%

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box2d-lite's Issues

FeaturePair.value not set correctly?

Hi Erin, Thank you for your great illustrative code, it is very good for learning rigid body dynamics.

From Arbiter::Update,

box2d-lite/src/Arbiter.cpp

Lines 40 to 50 in 227b71b

 Contact* cNew = newContacts + i; 

 int k = -1; 

 for (int j = 0; j < numContacts; ++j) 

 { 

 Contact* cOld = contacts + j; 

 if (cNew->feature.value == cOld->feature.value) 

 { 

 k = j; 

 break; 

 } 

 }

I think FeaturePair.value is used to distinguish contacts. While in Collide.cpp where contacts are computed, the only place to set value is in ClipVertex's constructor which set value=0.

box2d-lite/src/Collide.cpp

Lines 44 to 49 in 227b71b

 struct ClipVertex 

 { 

 ClipVertex() { fp.value = 0; } 

 Vec2 v; 

 FeaturePair fp; 

 };

Does it seem like this value is not correctly assigned for its purpose?

Thank you.

devide by zero error ?

https://github.com/netpipe/Luna/releases/

im not sure why but sometimes when the axe stops swinging on the main screen it crashes.

Collide separation name conflict

Hello, I'm trying to study it and try to rewrite box2dlite in c #, but I have a little problem I'm not sure in which Collide method used in the separation, you can show or put under "float separation = Dot (frontNormal, clipPoints2 [I] v) - front;" Change the name? Thank you very much! // I'm sorry I don't speak English so the above is from Google

repeated line on Arbiter.cpp

Hi Erin. Thank you for sharing your great articles for physics.
I'm studying game physics based on your articles

I found one repeated line on Arbiter.cpp

This is first calculation on 137

box2d-lite/src/Arbiter.cpp

Line 137 in d970582

 Vec2 dv = b2->velocity + Cross(b2->angularVelocity, c->r2) - b1->velocity - Cross(b1->angularVelocity, c->r1); 

However, it is repeated on 166

box2d-lite/src/Arbiter.cpp

Line 166 in d970582

 dv = b2->velocity + Cross(b2->angularVelocity, c->r2) - b1->velocity - Cross(b1->angularVelocity, c->r1); 

Question on order of bodies in arbiter code

In the Arbiter code, there is a comparison of less than in the body pointers for body 1 and 2. Why is this there? Why is this necessary?

box2d-lite/src/Arbiter.cpp

Lines 16 to 27 in 227b71b

 Arbiter::Arbiter(Body* b1, Body* b2) 

 { 

 if (b1 < b2) 

 { 

 body1 = b1; 

 body2 = b2; 

 } 

 else 

 { 

 body1 = b2; 

 body2 = b1; 

 }

I am porting this code to other language, and I am trying to figure some bugs that are appearing, and in this language, I can't do this type of comparisons on references, so I am just curious if I need to figure something to replicate this. Thanks!

erincatto / box2d-lite Goto Github PK

box2d-lite's People

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box2d-lite's Issues

FeaturePair.value not set correctly?

devide by zero error ?

Collide separation name conflict

repeated line on Arbiter.cpp

Question on order of bodies in arbiter code

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	Contact* cNew = newContacts + i;
	int k = -1;
	for (int j = 0; j < numContacts; ++j)
	{
	Contact* cOld = contacts + j;
	if (cNew->feature.value == cOld->feature.value)
	{
	k = j;
	break;
	}
	}

	struct ClipVertex
	{
	ClipVertex() { fp.value = 0; }
	Vec2 v;
	FeaturePair fp;
	};

	Arbiter::Arbiter(Body* b1, Body* b2)
	{
	if (b1 < b2)
	{
	body1 = b1;
	body2 = b2;
	}
	else
	{
	body1 = b2;
	body2 = b1;
	}