Unity Physical Camera如何使用真实摄像头内参

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通过OpneCV等工具提供的标定方法1，获得真实摄像头的针孔模型内参矩阵\(K\)：

\[K＝ {\begin{bmatrix} {f_x}&0&{c_x} \newline 0&{f_y}&{c_y} \newline 0&0&1 \end{bmatrix}}\]

Unity的Physcial Camera2仿真了真实世界的摄像头，可以将标定后的内参矩阵信息输入到Unity的Physcial Camera中，方便两者配合使用。

Unity中的转换方法：

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using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Runtime.InteropServices;
using UnityEngine;
using UnityEngine.UI;

public class MyCamera : MonoBehaviour
{
    public string camera_name = "Integrated Camera"; // USB Video Device //Integrated Camera //Virtual Camera
    public int width = 1280;
    public int height = 720;
    public int fps = 120;
    public float focal = 28F;
    public float fx = 1087.4199F;   
    public float fy = 1087.4199F;   
    public float cx = 640F; 
    public float cy = 360F;
    public float skew = 0F;
    public AspectRatioFitter fit;
    private RawImage cambackground = null;
    private Camera cam_obj = null;  
    private WebCamTexture cam = null;  
    private volatile Color32[] cam_data = null;
    private Texture2D tex = null;

    IEnumerator Start()
    {
        cambackground = GameObject.FindWithTag("CamBackground").GetComponent<RawImage>();
        cam_obj = GameObject.FindWithTag("MainCamera").GetComponent<Camera>();
        
        yield return Application.RequestUserAuthorization(UserAuthorization.WebCam);

        if (Application.HasUserAuthorization(UserAuthorization.WebCam))
        {
            WebCamDevice[] devices = WebCamTexture.devices;

            if (devices.Length == 0)
            {
                Debug.Log("No camera detected!");
                yield break;
            }

            bool find_camera = false;

            for (int i = 0; i < devices.Length; i++)
            {
                Debug.Log("Found camera:" + devices[i].name);
                if (camera_name.Equals(devices[i].name)) {
                    find_camera = true;
                }
            }

            if (!find_camera)
            {
                Debug.Log("Unable to find camera: " + camera_name + "\n");
                Debug.Log("Open the first camera" + devices[0].name + "\n");
                camera_name = devices[0].name;
            }

            cam = new WebCamTexture(camera_name, width, height, fps);

            WebCamTexture.allowThreadedTextureCreation = true;
            WebCamTexture.streamingTextureDiscardUnusedMips = true;

            cam.Play();
            
            width = cam.width;
            height = cam.height;
            
            // ******************************************************
            // Transfer Real Camera Inrinsic Parameters to Unity Physical Camera Parameters
            cam_obj.usePhysicalProperties = true;
            cam_obj.focalLength = focal;
            cam_obj.sensorSize = new Vector2(focal * width / fx,
                                          focal * height / fy);
            cam_obj.lensShift = new Vector2(-(cx - width * 0.5f) / width,
                                         (cy - height * 0.5f) / height);
            // ******************************************************
            
            Debug.Log(camera_name +" Running...\n");
        }
    }   

    void Update()
    {
        if (cam == null || !cam.isPlaying) return;

        if (cam_data == null)
        {
            cam_data = new Color32[width * height];
            tex = new Texture2D(width, height);
        }

        cam_data = cam.GetPixels32();
        tex.SetPixels32(cam_data);
        tex.Apply();
        cambackground.texture = tex;

        fit.aspectRatio = (float)cam.width / (float)cam.height;

    }
}

其中float focal为任意设定的参数（因为无法通过标定获得），一般选择一个靠近真实值的值。

  1. https://docs.opencv.org/master/dc/dbb/tutorial_py_calibration.html↩︎

  2. https://docs.unity3d.com/Manual/PhysicalCameras.html↩︎