display list doesn't work the proper way - c++

Question

I had already coded the display list.. and when i opened it again the next day -> gone..
niiice i thought.. i've wasted hours for nothing
and the next problem is.. i can't get it to work anymore
the display list actually works but not how it should.. textures are stretched somehow
i get my world from a text file.. each platform defined by start amount of x.. end amount of x
the y amount of the platform's bottom.. u and v (which i don't use) and filter for choosing texture.
setupworld is the function that reads from the text file and writes my variables into a structure.
Oh and numblocks is the number of platforms to display
void setupworld(){
float xstart,xend,ystart,u,v;
unsigned int filter;
FILE *filein;
char oneline[255];
filein=fopen("data/world.txt","rt");
readstr(filein,oneline);
sscanf(oneline, "Anzahl %d\n",&numblocks);
for (int loop=0;loop<numblocks; loop++)
{
readstr(filein,oneline);
sscanf(oneline,"%f %f %f %f %f %d",&xstart,&xend,&ystart,&u,&v,&filter);
block.data[loop].xstart=xstart;
block.data[loop].xend=xend;
block.data[loop].ystart=ystart;
block.data[loop].u=u;
block.data[loop].v=v;
block.data[loop].filter=filter;
}
fclose(filein);
return;}
BuildLists() creates my Display List, but first loads the png files and the world, cause they influence my display list... i had to rewrite this part of code and i just dont know where i made the mistake..
first loop is for creating the platforms and the 2nd one for blocks.. each platform consists of a number of 2x2 blocks simply next to eachother
GLvoid BuildLists(){
texture[0]=LoadPNG("data/rock_gnd.png");
texture[1]=LoadPNG("data/rock_wall2.png");
texture[2]=LoadPNG("data/pilz_test.png");
setupworld();
quad[0]=glGenLists(numblocks);
for(int loop=0;loop<numblocks;loop++)
{
GLfloat xstart,xend,ystart,u,v;
xstart=block.data[loop].xstart;
xend=block.data[loop].xend;
ystart=block.data[loop].ystart;
u=block.data[loop].u;
v=block.data[loop].v;
GLuint filter=block.data[loop].filter;
GLfloat blocks=(xend-xstart)/2.0f;
glNewList(quad[loop],GL_COMPILE);
glBindTexture(GL_TEXTURE_2D, texture[filter]);
for(int y=0;y<blocks;y++)
{
glBegin(GL_QUADS);
glTexCoord2f(0.0f,0.0f);
glVertex3f(xstart,ystart,-1.0f);
glTexCoord2f(1.0f,0.0f);
glVertex3f(xstart+((y+1)*2.0f),ystart,-1.0f);
glTexCoord2f(1.0f,1.0f);
glVertex3f(xstart+((y+1)*2.0f),ystart+2.0f,-1.0f);
glTexCoord2f(0.0f,1.0f);
glVertex3f(xstart,ystart+2.0f,-1.0f);
glEnd();
}
glEndList();
quad[loop+1]=quad[loop]+1;
}
}
the display list is compiled during initialisation just before enabling the 2d textures
this is how i call it during my actual code
int DrawWorld(GLvoid){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
GLfloat camtrans=-xpos;
glTranslatef(camtrans,0,0);
glPushMatrix();
for(int i=0;i<numblocks;i++)
{
glCallList(quad[i]);
}
glPopMatrix();
return TRUE; }
so this is it.. i think the mistake is in the BuildLists() function but i'm not sure anymore..
Here is the link to my screenshot.. as u see the textures look weird for some reason
http://www.grenzlandzocker.de/test.png

Answer 1

In your code:
quad[0]=glGenLists(numblocks);
creates numblocks display lists, but you only get the first display list id, and it is stored in quad[0]. Later, you use:
glNewList(quad[loop],GL_COMPILE);
where quad[loop] is undefined for loop != 0. You can instead use:
glNewList(quad[0] + loop,GL_COMPILE);
Because the ids for display lists are contiguous, starting with the value of quad[0]. You also need to modify your rendering code to:
glCallList(quad[0] + i);
For the same reason ...