Havok: Connecting your in-game camera to the Havok Visual Debugger

In projects using Havok, one thing that I've found invaluable is having the Havok Visual Debugger (HVD) visually match what you see in the game. Luckily, Havok provides a way for you to pass your camera's information to the HVD.

To send a camera's information to the HVD, you'll need the following:

• The position of the camera
• The forward/facing direction
• The up vector/axis
• The near and far plane distances
• The camera's FOV (field of view), in degrees (NOT radians)
• The name of the camera that you want to be seen and shown in the HVD.

Once you have all that information, you simply make the call to Havok's macro. I recommend creating an update function that you can call each frame when the camera updates, or when the renderer finally grabs the camera's information.

void UpdateVisualDebugger()
{
    Vector3 destination = m_position + m_forwardDir;

    HK_UPDATE_CAMERA( m_position, destination, m_upDir, m_nearPlaneDist, 
                      m_farPlaneDist, m_FOV, m_Name.c_str() );
}

Havok doesn't deal with STL types like strings, so you'll need to use .c_str() to send it the char pointer instead.

When you first connect the debugger to the game you will notice it isn't connected to the camera (this can be made to happen automatically, I may go over that in a future post). To connect to the camera, go to View->User Cameras->WhateverCameraNameYouChose.

If you're not properly or currently sending any camera information to Havok you may not see the 'User Cameras' option at all. Use a breakpoint to make sure you're hitting the macro during program execution.

If all worked well you should see your HVD window match your game's window. Please note that you can resize your HVD window and game window seperately, if you chose different aspect ratios for each window you will not get a perfect visual match between them, so try and keep them similar.

You'll also notice at the bottom of the HVD the name of the camera you're attached to. In my example above I've named my camera "Main Camera".

You may find that you're changing or creating cameras during the course of a game's execution, unfortunately Havok does not support automatically changing to new or different user cameras in the debugger when you change camera's from within game. I have put a support ticket in with them to consider including this in a future version. In the mean-time if you want this functionality you will need to have a user camera name that represents whatever camera happens to be active at the time. I recommend sending the active camera each frame under a generic name like "Active Camera" or "Main Camera", as well as the active camera by its unique name like "Character Camera". This will allow the developer to choose to always see the active camera from within Havok, or choose a unique camera and not have it switch automatically.