How To Freeze the Video Background

This page concerns the Vuforia Engine API version 9.8 and earlier. It has been deprecated and will no longer be actively updated.

These code snippets show how to freeze the video background without stopping the tracker.

The video background freezing functionality is enabled by the begin() method of the Renderer class, which optionally accepts a custom State parameter.

The following code sample shows how this functionality can be enabled by holding the State object at a given frame and reusing the same state in a subsequent frame:

C++:

Vuforia::State frozenState; // adding global variable

void
renderFrame(JNIEnv* env, jobject obj, bool renderFrozenFrame, bool freezeCurrent)
{   
    // Clear color and depth buffer
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    Vuforia::State state;
    if ( renderFrozenFrame )
    {
        // Get the state from Vuforia and mark the beginning of a rendering section
        state = Vuforia::Renderer::getInstance().begin( frozenState );
    }
    else
    {
        state = Vuforia::Renderer::getInstance().begin();
        if ( freezeCurrent )
        {
            frozenState = state;

            // Release camera
            Vuforia::CameraDevice::getInstance().stop();
            Vuforia::CameraDevice::getInstance().deinit();
        }
    }
     
    // Explicitly render the Video Background
    Vuforia::Renderer::getInstance().drawVideoBackground();

    // Your rendering code  
     
     
    // Finish rendering
    Vuforia::Renderer::getInstance().end();
}

Java:

State frozenState;

void
renderFrame(bool renderFrozenFrame, bool freezeCurrent)
{   
    // Clear color and depth buffer
    GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);

    State state;
    if ( renderFrozenFrame )
    {
        // Get the state from Vuforia and mark the beginning of a rendering section
        state = Renderer.getInstance().begin( frozenState );
    }
    else
    {
        state = Renderer.getInstance().begin();
        if ( freezeCurrent )
        {
            frozenState = state;

            // Release camera
            CameraDevice.getInstance().stop();
            CameraDevice.getInstance().deinit();
        }
    }
     
    // Explicitly render the Video Background
    Renderer.getInstance().drawVideoBackground();

    // Your rendering code  
     
     
    // Finish rendering
    Renderer.getInstance().end();
}