what is wrong with my 2D Interpolation C code

#include <GL/glut.h>
#include <GL/gl.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define N 200
typedef struct vertex{

    float x;                  //  x position of the point
    float y;                  //开发者_StackOverflow社区  y position of the point
    float r;                  //  red color component of the point
    float g;                  //  green color component of the point
    float b;                  //  blue color component of the point
    char isVisited;
}Vertex;

Vertex *borderLines,*interPolationLines;
int vertex_Count;// total vertex
int counter;//counts matched y coordinates 
FILE *f,*g;

void readTotalVertexCount(){

    if((f = fopen("vertex.txt","r"))==NULL){
        printf("File could not been read\n");
        return ;
    }
    fscanf(f,"%d",&vertex_Count);

    /*if((g = fopen("points.txt","w"))==NULL){

        return ;
    }*/
}

void readVertexCoordinatesFromFile(){

    Vertex v[vertex_Count];
    borderLines = (Vertex *)calloc(N*vertex_Count,sizeof(Vertex));
    interPolationLines = (Vertex *)calloc(N*N*(vertex_Count-1),sizeof(Vertex));

    int i = 0;int j;
    //read vertexes from file
    while(i<vertex_Count){
        fscanf(f,"%f",&(v[i].x));
        fscanf(f,"%f",&(v[i].y));
        fscanf(f,"%f",&(v[i].r));
        fscanf(f,"%f",&(v[i].g));
        fscanf(f,"%f",&(v[i].b));
        //printf("%f %f \n",v[i].x,v[i].y);  
        i++;
    }

    Vertex *borderLine,*temp;
    float k,landa;

    // draw border line actually I am doing 1D Interpolation with coordinates of my vertexes
    for (i = 0;i < vertex_Count;i++){
        int m = i+1;
        if(m==vertex_Count)
            m = 0;

        borderLine = borderLines + i*N;

        for(j = 0;j < N; j++){
            k = (float)j/(N - 1);
            temp = borderLine + j;
            landa = 1-k;
            //finding 1D interpolation coord. actually they are borders of my convex polygon 
            temp->x = v[i].x*landa + v[m].x*k;
            temp->y = v[i].y*landa + v[m].y*k;
            temp->r = v[i].r*landa + v[m].r*k;
            temp->g = v[i].g*landa + v[m].g*k;
            temp->b = v[i].b*landa + v[m].b*k;
            temp->isVisited = 'n'; // I didn't visit this point yet
            //fprintf(g,"%f %f %f %f %f\n",temp->x,temp->y,temp->r,temp->g,temp->b);
        }
    }
    /* here is actual place I am doing 2D Interpolation
       I am traversing along the border of the convex polygon and finding the points have the same y coordinates
       Between those two points have same y coord. I am doing 1D Interpolation*/
    int a;counter = 0;
    Vertex *searcherBorder,*wantedBorder,*interPolationLine;
    int start = N*(vertex_Count);   int finish = N*vertex_Count;

    for(i = 0;i< start ;i++){

        searcherBorder = i + borderLines;

        for(j = i - i%N + N +1; j< finish; j++){

            wantedBorder = j + borderLines;
            if((searcherBorder->y)==(wantedBorder->y) && searcherBorder->isVisited=='n' && wantedBorder->isVisited=='n'){
                //these points have been visited                                            
                searcherBorder->isVisited = 'y';
                wantedBorder->isVisited = 'y';

                interPolationLine = interPolationLines + counter*N;
                //counter variable counts the points have same y coordinates.
                counter++;
                //printf("%d %d %d\n",i,j,counter);
                //same as 1D ınterpolation     
                for(a= 0;a< N;a++){

                    k = (float)a/(N - 1);
                    temp = interPolationLine + a;
                    landa = 1-k;
                    temp->x = (wantedBorder->x)*landa + (searcherBorder->x)*k;
                    temp->y = (wantedBorder->y)*landa + (searcherBorder->y)*k;
                    temp->r = (wantedBorder->r)*landa + (searcherBorder->r)*k;
                    temp->g = (wantedBorder->g)*landa + (searcherBorder->g)*k;
                    /*if(temp->x==temp->y)
                        printf("%f  %f \n",wantedBorder->x,searcherBorder->x);*/
                    temp->b = (wantedBorder->b)*landa + (searcherBorder->b)*k;

                }
            }
        }
    }

    fclose(f);
}

void display(void){

    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0,1.0,1.0);

    int i,j;
    Vertex *interPol,*temp;

    glBegin (GL_POINTS);

    for(i = 0;i< counter;i++){
        interPol = interPolationLines + i*N;
        for(j = 0;j< N;j++){
            temp = interPol + j;
            glColor3f((temp)->r,(temp)->g,(temp)->b);
            //fprintf(g,"%f %f \n",(temp)->x,(temp)->y);
            glVertex2f ((temp)->x,(temp)->y);
        }
    }
    //printf("%d\n",counter);
    fclose(g);
    glEnd ();
    glFlush();
}

void init(void){
    glutInitDisplayMode( GLUT_RGB | GLUT_SINGLE);
    glutInitWindowSize(900,500);
    glutInitWindowPosition(200,100);
    glutCreateWindow("2D InterPolation");
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);
    glShadeModel(GL_SMOOTH);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);  
}

int main(int argc, char** argv)
{
    readTotalVertexCount();
    readVertexCoordinatesFromFile();
    glutInit(&argc,argv);
    init();
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}

I am implementing 2D Interpolation of a convex polygon and my code does not care about concav.my code works for some convex polygons but for others fail.For those my code fails it does not draw middle of the polygon.it only draws an upper and lower triangle.it reads vertexes from file vertex.txt and its format:x co,y co,red,green,blue color info of that point like below and for the values below my code fails.Thanks for replies in advance.I will get mad.

7
0.9 0.4 1.0 0.0 1.0
0.8 0.2 1.0 0.0 1.0
0.5 0.1 1.0 0.0 0.0
0.3 0.3 0.0 0.0 1.0
0.3 0.35 0.0 0.0 1.0
0.4 0.4 0.0 1.0 0.0
0.6 0.5 1.0 1.0 1.0

Without fully debugging your program, I'm suspicious of the line that says, for(j = i - i%N + N +1; j< finish; j++){. I don't know exactly what you're intending to do, but it just looks suspicious. Furthermore, I would recommend a different algorithm:

1. Trace around the polygon
2. Mark any edges that span the desired y-value
3. Corner cases aside, there's only a solution if you find exactly two hits.
4. Calculate the intersection of the edges with the y-value
5. Perform the x-interpolation

Also, concise questions are better than, "Why doesn't my program work?" Forgive me but it feels like a homework problem.

Note: Should this be a comment instead of an answer? I'm new here...