Importing an existing 3D object in an OpenGL program

Sorry if this is a FAQ.

I would like to know how to import a 3D object, created by a 3D program (as 3Dmax) in my openGL code i've written. To perform some manipulations (rotation) on it in my own program. Are there some converters or export utils. to port existing objects to OpenGl coordinades.

Thanks for pointing me in the right direction.

Stijn

[Bob]

You can download 3D Exploration . 3DE can load several different formats, and export the object to OpenGL-displaylists (and a number of other formats aswell).

Or you can go find the specifications for a certain fileformat and do a loader yourself. .ASE-files (3D Studio can export this format) is extremely easy to understand if you want to make a loader yourself.

[masterpoi]

Originally posted by Stijn:
Sorry if this is a FAQ.

I would like to know how to import a 3D object, created by a 3D program (as 3Dmax) in my openGL code i've written. To perform some manipulations (rotation) on it in my own program. Are there some converters or export utils. to port existing objects to OpenGl coordinades.

Thanks for pointing me in the right direction.

Stijn

This was posted on flipcode a while a go:
struct CVertex
{
float x,y,z;
};

struct CPolygon
{
int verts[3];
};

struct CModel
{
CVertex* verts;
int numverts;
CPolygon* polys;
int numpolys;
};

CModel g_model;


// Load3DS
//
// Load a .3ds file into memory for parsing
//
int Load3DS(char* filename)
{
ifstream file;
bool doneloading = false;
int filelength;
char* memfile; // file loaded into memory

// load entire file into memory (easier to deal with)
file.open(filename, ios::binary);
file.seekg(0, ios::end);
filelength = file.tellg();
memfile = new char[filelength];
file.seekg(0, ios::beg);
file.read(memfile, filelength);
// parse it
EatChunk(memfile);
delete memfile;
return 0;
}

// EatChunk
//
// This function recursively handles chunks
// in a .3ds file. When the function exits,
// the return value (i) should be the length
// of the current chunk. Right now we only
// create one model (the first one listed in
// the file) and read in verts and polys only.
// To grab other info from the file, create
// a new case label in the switch statement
// for the chunk type you want to react to.
//
long EatChunk(char* buffer)
{
short chunkid;
long chunklength;
int i = 0; // index into current chunk
int j;

chunkid = *(short*)(buffer);
chunklength = *(long*)(buffer+2);
i = 6;
switch (chunkid)
{
case 0x4D4D: // main file
while ((*(short*)(buffer+i) != 0x3D3D) &&
(*(short*)(buffer+i) != 0xB000))
i += 2;
break;
case 0x3D3D: // editor data
break;
case 0x4000: // object description
while (*(buffer+(i++)) != 0); // get past string description
break;
case 0x4100: // triangular polygon list
break;
case 0x4110: // vertex list
if (g_model.numverts == NULL)
{
g_model.numverts = *(short*)(buffer+i);
i+=2;
g_model.verts = new CVertex[g_model.numverts];
for (j=0;j<g_modelnumverts;j++)
{
g_model.verts[j].x = *(float*)(buffer+i);
i+=4;
g_model.verts[j].y = *(float*)(buffer+i);
i+=4;
g_model.verts[j].z = *(float*)(buffer+i);
i+=4;
}
}
else
i = chunklength;
break;
case 0x4120:
if (g_model.numpolys == NULL)
{
g_model.numpolys = *(short*)(buffer+i);
i+=2;
g_model.polys = new CPolygon[g_model.numpolys];
for (j=0;j<numpolys;j++)
{
g_model.polys[j].verts[0] = *(short*)(buffer+i);
i+=2;
g_model.polys[j].verts[1] = *(short*)(buffer+i);
i+=2;
g_model.polys[j].verts[2] = *(short*)(buffer+i);
i+=2;
i+=2; // skip face info
}
}
else
i = chunklength;
break;
default:
i = chunklength; // skips over rest of chunk (ignores it)
break;
}

// eat child chunks
while (i < chunklength)
i += EatChunk(buffer+i);
return chunklength;
}