C++ : como usar Multitarefa?

[Cambalinho]

estou a tentar usar Multitarefa no C++, mas estou a ter dificuldades. como se usa?
todo este código está dentro de 1 classe.

#include <pthread.h>

struct Pixel
    {
        float X = 0;
        float Y = 0;
        float Z = 0;
        BYTE R = 0;
        BYTE G = 0;
        BYTE B = 0;
    };

    
void *DrawPixel(void *threadarg)
    {
        struct Pixel *Pix;
        Pix = (struct Pixel *) threadarg;
        //For every steps we calculate the perspective:
        //Avoiding division by zero:
        float EyeDistance = 500;// doing these i avoid the black\empty vertical lines
        const float d = EyeDistance+Pix->Z; // Note that Z==0 is irrelevant here
        const float Perspective = (d != 0) ? (EyeDistance/d) : 0;

        //The 3D to 2D convertion(i use 300 of eye distance, but we can change it):
        int PosX = Pix->X*Perspective;
        int PosY = Pix->Y*Perspective;


        //Draw the pixel on valid positions:
        if(Pix->Z>=0 && PosX<Width && PosX>=0 && PosY<Height && PosY>=0)
        {
            size_t pixelOffset = PosY * scanlineSize + PosX * pixelSize;
            int PosR = pixelOffset+2;
            int PosG = pixelOffset+1;
            int PosB = pixelOffset+0;

            Pixels[PosR]=Pix->R;
            Pixels[PosG]=Pix->G;
            Pixels[PosB]=Pix->B;
        }
        pthread_exit(NULL);

    }
//use it inside the class:
//Getting RGB from the color:
        int R = GetRValue(LineColor);
        int G = GetGValue(LineColor);
        int B = GetBValue(LineColor);
        pthread_t Draw;
        Pixel PixeImage;
        PixeImage.X = X;
        PixeImage.Y = Y;
        PixeImage.Z = Z;
        PixeImage.R = R;
        PixeImage.G = G;
        PixeImage.B = B;


        int i=0;
        do
        {
            PixeImage.X = X;
            PixeImage.Y = Y;
            PixeImage.Z = Z;
            pthread_create(&Draw, NULL, &DrawPixel,(void*) &PixeImage);
            //................

ao usar esta ultima linha, eu obtenho 1 erro:
"cannot convert 'void* (image::*)(void*)' to 'void* (*)(void*)'"
estou a tentar fazer esta alteração por este tutorial: https://www.tutorialspoint.com/cplusplus/cpp_multithreading.htm