Real-Time Physics Simulation Forum

Re: btCompoundShape of convex hulls not rendering in BasicExample

2021-09-11T19:05:02+00:00

Typically math libraries that have been optimized will NOT initialize object components to default values in the default ctor. This to avoid wasted CPU cycles for the cases where the default values are immediately overwritten. As such they require the Application developer to explicitly initialize.

As I recall, sometime around 2011 or so the Havok physics math library took this to the next level and eliminated the copy ctor and normal math operators that used it. As a consequence code that used to be expressible in one line...

Code:

Vector3 C = A + delta * (B - A)

...could only be done over several lines:

Code:

Vector3 C(B);C.subtract(A);C.multiply(delta);C.add(A);

The new method was more verbose but less work was hidden by C++ abstraction and the compiled binary would use fewer byte codes.

Statistics: Posted by drleviathan — Sat Sep 11, 2021 7:05 pm

Re: btCompoundShape of convex hulls not rendering in BasicExample

2021-09-10T22:12:52+00:00

Thank you, it gets displayed now. I wasn't aware I need to call setIdentity() to load the defaults.

Statistics: Posted by zb10948 — Fri Sep 10, 2021 10:12 pm

Re: btCompoundShape of convex hulls not rendering in BasicExample

2021-09-10T21:27:32+00:00

In the btCompoundShape case your testModelTransform is left uninitialized when you pass it to createRigidBody(). Does the problem go away when you initialize it to something reasonable?

Statistics: Posted by drleviathan — Fri Sep 10, 2021 9:27 pm

btCompoundShape of convex hulls not rendering in BasicExample

2021-09-10T16:32:56+00:00

Hello,

I've been looking into bullet for some simulation of rigid bodies with multiple hulls or collision sections. For start i use infrastructure provided by BasicExample for some POCs. By creating two btConvexHulls and their bodies I get the exact shapes on screen. When I try to do the same via btCompoundShape::addChildShape() and then make a single body, there's nothing in the visualization.

Is this an issue in approach or a limit of a built in visualizer?

Code:

    btTransform t1;    m_collisionShapes.push_back(collisionModel->meshes[0]->generatedHull);    createRigidBody(0., t1, collisionModel->meshes[0]->generatedHull);    btTransform t2;    t2.setOrigin(btVector3(-0.5, 0, 0));    m_collisionShapes.push_back(collisionModel->meshes[1]->generatedHull);    createRigidBody(0., t2, collisionModel->meshes[1]->generatedHull);

Code:

    btCompoundShape * compound = new btCompoundShape();    btTransform t1;    compound->addChildShape(t1, collisionModel->meshes[0]->generatedHull);        btTransform t2;    t2.setOrigin(btVector3(-0.5, 0, 0));    compound->addChildShape(t2, collisionModel->meshes[1]->generatedHull);        btTransform testmodelTransform;    m_collisionShapes.push_back(compound);    createRigidBody(0., testmodelTransform, compound);

Statistics: Posted by zb10948 — Fri Sep 10, 2021 4:32 pm