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DominicHughes

OpenGL
How to automatically create displaylists in opengl 3.0?

11 posts in this topic

I have my 3d model wavefront obj c++ parser using sscanf functions,etc,etc

and I wanted to know how I can load more then one model with the parser without it deleting the current model because the parser only uses one displaylist so I looked into it and I think I need to create a automatic diplaylist creation and use it automatically but I don't really know how to do it?.

Could anyone give me some tips or ideas on how to do this?.


OpenGL 3.0
Win32 API
C++
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What are you doing now so that you cannot have more than one? I don't see how there should be any problem with multiple objects if you just allocate and return the necessary resources when you load the object.
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Well I'm basically parsing the data found in szFileName in WIN32 file dialog with this function call but it doesn't create more then one displaylist and I don't know how to make it work so the function automatically creates displaylists. the code below is that function BrotherBob?[CODE]
int ModelLoad(const char *filename)
{
vector<string*> values;
vector<cordinate*> vertex;
vector<face*> faces;
vector<cordinate*> normals;
ifstream file(filename);
if(!file.is_open())
{
cout << "Model Load Failed :( make shore to set your blender or 3ds max settings correctly and or use the right file format" << endl;
return -1;
}
char buffer[256];
while(!file.eof())
{
file.getline(buffer, 256);
values.push_back(new string(buffer));
}
for(int i=0;i<values.size();i++)
{

if(values[i]->c_str()[0] =='#')
continue;
else if(values[i]->c_str()[0] == 'v' && values[i]->c_str()[1] == ' ')
{

float tmpx, tmpy, tmpz;
sscanf(values[i]->c_str(), "v %f %f %f", &tmpx, &tmpy, &tmpz);
vertex.push_back(new cordinate(tmpx, tmpy, tmpz));
}

else if(values[i]->c_str()[0]=='v' && values[i]->c_str()[1]=='n') //if normal vector
{
float tmpx,tmpy,tmpz; //do the same thing
sscanf(values[i]->c_str(),"vn %f %f %f",&tmpx,&tmpy,&tmpz);
normals.push_back(new cordinate(tmpx,tmpy,tmpz));
}

else if(values[i]->c_str()[0] == 'f')
{
int a, b, c, d, e;
if(count(values[i]->begin(), values[i]->end(),' ') == 3)
{

sscanf(values[i]->c_str(),"f %d//%d %d//%d %d//%d",&a,&b,&c,&b,&d,&b);
faces.push_back(new face(b,a,c,d));


}
else
{
sscanf(values[i]->c_str(),"f %d//%d %d//%d %d//%d %d//%d",&a,&b,&c,&b,&d,&b,&e,&b);
faces.push_back(new face(b,a,c,d,e));
}

}

}

int num; //the id for the list
num=glGenLists(1); //generate a uniqe
glNewList(num,GL_COMPILE); //and create it
for(int i=0;i<faces.size();i++)
{
if(faces[i]->four) //if it's a quad draw a quad
{
glBegin(GL_QUADS);
//basically all I do here, is use the facenum (so the number of the face) as an index for the normal, so the 1st normal owe to the first face
//I subtract 1 because the index start from 0 in C++
glNormal3f(normals[faces[i]->facenum-1]->x,normals[faces[i]->facenum-1]->y,normals[faces[i]->facenum-1]->z);
//draw the faces
glVertex3f(vertex[faces[i]->faces[0]-1]->x,vertex[faces[i]->faces[0]-1]->y,vertex[faces[i]->faces[0]-1]->z);
glVertex3f(vertex[faces[i]->faces[1]-1]->x,vertex[faces[i]->faces[1]-1]->y,vertex[faces[i]->faces[1]-1]->z);
glVertex3f(vertex[faces[i]->faces[2]-1]->x,vertex[faces[i]->faces[2]-1]->y,vertex[faces[i]->faces[2]-1]->z);
glVertex3f(vertex[faces[i]->faces[3]-1]->x,vertex[faces[i]->faces[3]-1]->y,vertex[faces[i]->faces[3]-1]->z);
glEnd();
}

else
{
glBegin(GL_TRIANGLES);
glColor3f(1, 0, 0);
glNormal3f(normals[faces[i]->facenum-1]->x,normals[faces[i]->facenum-1]->y,normals[faces[i]->facenum-1]->z);
glColor3f(0, 0, 0);
glVertex3f(vertex[faces[i]->faces[0]-1]->x,vertex[faces[i]->faces[0]-1]->y,vertex[faces[i]->faces[0]-1]->z);
glColor3f(0, 1, 1);
glVertex3f(vertex[faces[i]->faces[1]-1]->x,vertex[faces[i]->faces[1]-1]->y,vertex[faces[i]->faces[1]-1]->z);
glColor3f(0, 1, 0);
glVertex3f(vertex[faces[i]->faces[2]-1]->x,vertex[faces[i]->faces[2]-1]->y,vertex[faces[i]->faces[2]-1]->z);
glEnd();
}
}
glEndList();
//delete everything to avoid memory leaks
for(int i=0;i<values.size();i++)
delete values[i];
for(int i=0;i<faces.size();i++)
delete faces[i];
for(int i=0;i<normals.size();i++)
delete normals[i];
for(int i=0;i<vertex.size();i++)
delete vertex[i];
return num; //return with the id

}
[/CODE] Edited by DarkHorseKnight
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Your function allocates a display list, builds it, and returns the handle to the newly created display list. What is it with it that doesn't work if you call it more than once?
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When the function is called if there is already a model on the frustum it dissappears? I have checked thanks to gdebugger with the camera and I can't find the model anywhere. I looked at my code

This is the function call and this is called after win32 gets the filename

[CODE]
cube=ModelLoad(szFileName);
[/CODE]

maybe when I call this again it deletes the contents of cube since cube is what holds the displaylist? Edited by DarkHorseKnight
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There is nothing in the function you posted that removes anything from anywhere. The content of previous display lists are not affected at all, since, as I said, your function allocates a [i]new[/i] display list each time it's called; it doesn't overwrite or delete anything, not from the screen nor from any display lists. If you're having problems with your display lists being removed, then it's somewhere else.
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Ah ha it looks like when ever the filename is changed it makes the model on the frustum "before" the next filename dissappear ? strange hmmm more exploring in this code is required. Edited by DarkHorseKnight
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The problem is in this code below what is happening is szFileName can only store one filename at a time so I need to know how to store more then one filename do you know how I could do that brother bob?[CODE]
switch(LOWORD(wParam))
{
case ID_BOX:
{



ZeroMemory(&ofn, sizeof(ofn));
ofn.lStructSize = sizeof(ofn); // SEE NOTE BELOW
ofn.hwndOwner = hwnd;
ofn.lpstrFilter = ".OBJ (*.obj)\0*.obj\0All Files (*.*)\0*.*\0";
ofn.lpstrFile = szFileName;
ofn.nMaxFile = MAX_PATH;
ofn.Flags = OFN_EXPLORER | OFN_FILEMUSTEXIST | OFN_HIDEREADONLY | OFN_LONGNAMES;
ofn.lpstrDefExt = "obj";


if(GetOpenFileName(&ofn))
{
cube=ModelLoad(szFileName);

}


}
break;
[/CODE] Edited by DarkHorseKnight
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So you are just keeping one display list and overwriting the previous display list handle when you load a new? If you want multiple objects, then you also need to store multiple handles. How you should solve that depends on what you want to do.

For example, make cube a list of handles instead of just one handle.
[source]
std::vector<GLuint> cube;
[/source]
Append the new object to the list of objects.
[source]
cube.push_back(ModelLoad(szFileName));
[/source]
And then loop over all objects and draw them instead of just drawing one object.
[source]
for(std::vector<GLuint>::iterator I = cube.begin(); I != cube.end(); ++I) {
glDrawList(*I);
}
[/source]
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