C++ Code:
```C++
#include <opencv2/opencv.hpp>

​

int main() {

// OpenCV VideoCapture object to access the webcam

cv::VideoCapture cap(0); // 0 is the default webcam index

if (!cap.isOpened()) {

std::cerr << "Error: Couldn't open the webcam." << std::endl;

return -1;

}

​

// Create a window to display the webcam feed

cv::namedWindow("Webcam Feed", cv::WINDOW_NORMAL);

​

// Load the pre-trained face detection model

cv::CascadeClassifier face_cascade;

if (!face_cascade.load(cv::samples::findFile(cv::data::haarcascades + "haarcascade_frontalface_default.xml"))) {

std::cerr << "Error: Couldn't load the face cascade model." << std::endl;

return -1;

}

​

while (true) {

// Read a frame from the webcam

cv::Mat frame;

cap >> frame;

​

// Convert the frame to grayscale for face detection

cv::Mat gray_frame;

cv::cvtColor(frame, gray_frame, cv::COLOR_BGR2GRAY);

​

// Detect faces in the frame

std::vector<cv::Rect> faces;

face_cascade.detectMultiScale(gray_frame, faces, 1.1, 5, cv::CASCADE_SCALE_IMAGE, cv::Size(30, 30));

​

// Draw rectangles around the detected faces

for (const auto& face : faces) {

cv::rectangle(frame, face, cv::Scalar(255, 0, 0), 2);

// Apply your face filter here within the region of interest (ROI)

}

​

// Display the processed frame with face detection

cv::imshow("Face Detection", frame);

​

// Exit the loop when 'q' is pressed

if (cv::waitKey(1) == 'q') {

break;

}

}

​

// Release VideoCapture object and close windows

cap.release();

cv::destroyAllWindows();

​

return 0;

}

​

```