Havok: Setting mesh color in the Visual Debugger, Part 2

In part 1 of this series I showed you how to colorize your physics meshes in the Havok Visual Debugger (HVD). However as you may have noticed, this only works for colorizing meshes that are already loaded in the HVD, so if you connect the HVD to the game after those colors have been set you will not see that information. Here's a simple way to get around that problem.

You program is likely directly using an hkVisualDebugger, what you will need to do is derived a new class from hkVisualDebugger. The hkVisualDebugger class has an m_clients variable, but it's access is protected, and there is no accessor to its information in hkVisualDebugger so unless you have the actual source code for Havok, you're going to need to derive your own class from hkVisualDebugger so you can create an accessor to the data that you need.

Create a new header file in your project, name it 'PhysicsVisualDebugger' or whatever class name you would like to use. The code below is the entire class, no .cpp file is needed.

#pragma once

#ifndef __PhysicsVisualDebugger_h_
#define __PhysicsVisualDebugger_h_

#include <common\visualize\hkvisualdebugger.h>

class PhysicsVisualDebugger : public hkVisualDebugger
{
public:
    PhysicsVisualDebugger(const hkArray<hkProcessContext*>,
                          const class hkVtableClassRegistry* classReg = HK_NULL)
         : hkVisualDebugger(contexts, classReg)
    {}

    virtual ~PhysicsVisualDebugger() {};

    unsigned int GetNumClients() const { return m_clients.getSize(); }
};

#endif //__PhysicsVisualDebugger_h_

Make sure any place you were using an 'hkVisualDebugger' that you're not using your new class you've just made.

The goal we're aiming for is to know when somebody connects the HVD to your program. The GetNumClients() above will return to you the number of current clients connected, if you call it at the appropriate time you can compare it to check if that number has just increased.

In my example below, 'm_pDebugger' is a pointer to a 'PhysicsVisualDebugger'. Put this code wherever you're currently stepping the HVD.

unsigned int numConnections = m_pDebugger->GetNumClients();

// Update the debuggers (which also checks for new clients)
m_pDebugger->step(m_fStepLength);

// If there are now more connections than before the update
if ( m_pDebugger->GetNumClients() > numConnections )
{
    // This is where you will want to go through all physics
    // objects and have to re-send their color info to the
    // debugger.
    UpdateDebuggerInfoForAllEntities();
}

Notice we query the number of connections before stepping the debugger, store that number, and then after stepping the debugger we query for number of connections again. If the number of clients has increased, then you should find a way of having all of your objects resend their color information to the HVD. In my case whenever I add an object to the Havok world, I keep track of its pointer in a list so I can call a function on everything in that list at any time to have them refresh their information for the HVD.