MD3 model loader in C++

[Selphie142]

I'm trying to create a model loader for md3 files using C++. I have some tutorials and source code for some md2 model loaders. I also have the file format of md3 files from Wiki.

I'd like to have my models animated and with textures but at the moment I'm just having problems loading the model at all.

Any help would be appreciated.

[^misantropia^]

That's rather broad. Do you have specific issues you are running into?

[Selphie142]

I'm currently having issues with understanding the code to get my loader to get read the information from the md3 file. I really don't know where to begin. I found some pages about md2 but it all looks so complicated and is really daunting.

[^misantropia^]

That's still not much to go on. =)

CS 101: break up the problem in smaller problems. Repeat until you can't break it up further. Think about how to approach each problem. Think some more. Start coding.

[bitWISE]

If something isn't working right, the most likely problem is you're not parsing the data properly. Being wrong by even 1-bit can have catastrophic consequences when you're talking about parsing thousands of array elements from a binary file. Focus on just loading the model data, and outputting it to the console before you worry about rendering (an application of what misantropia said). Try working with a simple model that you know for a fact has X number of verts/faces/tags etc. Once you get the counts perfect, move on to rendering.

Here is a solid guide to the format:
http://icculus.org/~phaethon/q3a/formats/md3format.html

If you really get stumped, take a peak at the q3 engine source.

[Selphie142]

So, I've been trying to get something to work and I have managed to get all the data to read out properly (in text format) with the exception of multiple surfaces but I'm going to address that issue later as I'm just using a single surface model at the moment.

I also managed to get some triangles appear in the applet window, nothing like the model but it was something. While I was attempting to get it to produce the actual model I appear to have broken it. Now my applet just crashes without outputting any text or anything.

My Main.cpp was given to me by my lecturer and only defines the way that the model is drawn (colour, rotation etc). My GameObject.h is as follows:

Code: Select all

#include <GL/gl.h>
#include <stdlib.h>
#include <string>
#include <iostream>
#include <fstream>

using namespace std;

#ifndef GAMEOBJECT_H_
#define GAMEOBJECT_H_

class GameObject
{
public:
	GameObject();
	GameObject(const char * filename);
	virtual ~GameObject();

	virtual void draw();

private:

	struct md3_header
	{
		int ident;
		int version;

		char name[64];

		int flags;
		int num_frames;
		int num_tags;
		int num_surfaces;
		int num_skins;

		int ofs_frames;
		int ofs_tags;
		int ofs_surfaces;
		int ofs_eof;
	};

	typedef float vec3[3];

	struct md3_frame_header
	{
		vec3 min_bounds;
		vec3 max_bounds;
		vec3 local_origin;
		float radius;
		char name[16];
	};

	struct md3_tag_header
	{
		char name[64];
		vec3 origin;
		vec3 axis[3];
	};

	struct md3_surface_header
	{
		int ident;
		char name[64];

		int flags;
		int num_frames;
		int num_shaders;
		int num_verts;
		int num_triangles;

		int ofs_triangles;
		int ofs_shaders;
		int ofs_st;
		int ofs_xyznormal;
		int ofs_end;
	};

	struct md3_shader_header
	{
		char name[64];
		int shader_index;
	};

	struct md3_triangle_header
	{
		int indexes[3];
	};

	struct md3_texcoord_header
	{
		float st[2];
	};

	struct md3_vertex_header
	{
		short coord[3];
		char normal[2];
	};
	vec3 * vertices;

		int num_frames;
		md3_frame_header * frames;
		int num_vertices;
		md3_vertex_header * verts;
		int num_surfaces;
		md3_surface_header * surfaces;
		int num_triangles;
		md3_triangle_header * triangles;
		int num_tags;
		md3_tag_header * tags;
		int num_shaders;
		md3_shader_header * shaders;
		md3_texcoord_header * coords;
};

#endif

My GameObject.cpp is:

Code: Select all

#include "GameObject.h"

GameObject::GameObject()
{
}

GameObject::GameObject(const char * filename) {
	ifstream md3file;
	md3file.open(filename, ios::in|ios::binary);

	//C Stuff
	md3_header * md3header = (struct md3_header*)
			malloc(sizeof(struct md3_header));

	md3file.read((char *) md3header, sizeof (struct md3_header));

	if ((md3header->ident != 860898377) || (md3header->version <15)) {
	//Error!
		cerr << "Error: bad version or identifier" << endl;
}

	this->triangles = (md3_triangle_header *)
				calloc(this->surfaces->num_triangles,sizeof(struct md3_surface_header));
			md3file.seekg(this->surfaces->ofs_triangles, ios::beg);
			md3file.read((char*)triangles,sizeof (struct md3_triangle_header)* surfaces->num_triangles);

	this->surfaces= (md3_surface_header *)
			calloc(md3header->num_surfaces,sizeof(struct md3_surface_header));
	md3file.seekg(md3header->ofs_surfaces,ios::beg);
	md3file.read((char *) this->surfaces, sizeof(struct md3_surface_header));


	this->verts = (md3_vertex_header *)
		calloc(this->surfaces->num_verts,sizeof(struct md3_vertex_header));
	md3file.seekg(surfaces->ofs_xyznormal, ios::beg);
	md3file.read((char*)verts,sizeof (struct md3_vertex_header)* surfaces->num_verts);

	this->surfaces = (struct md3_surface_header *)
			calloc (md3header->ofs_surfaces, sizeof(struct md3_surface_header));
	md3file.seekg(md3header->ofs_surfaces,ios::beg);
	md3file.read((char*)surfaces, sizeof (struct md3_surface_header)* md3header->num_surfaces);


	this->frames = (struct md3_frame_header *)
			calloc (md3header->num_frames, sizeof(struct md3_frame_header));
	md3file.seekg(md3header->ofs_frames, ios::beg);
	md3file.read((char *) frames, sizeof (struct md3_frame_header) * md3header->num_frames);

	this->tags = (struct md3_tag_header *)
			malloc (sizeof(struct md3_tag_header) * md3header->num_tags);
	md3file.seekg(md3header->ofs_tags,ios::beg);
	md3file.read((char*)tags,sizeof(struct md3_tag_header)* md3header->num_tags);


			cout << "Ident: " << md3header->ident <<endl;
			cout << "Version: " << md3header->version <<endl;
			cout << "Name: " << md3header->name <<endl;
			cout << "Flags: " << md3header->flags <<endl;
			cout << "Num Frames: " << md3header->num_frames <<endl;
			cout << "Num_tags: " << md3header->num_tags <<endl;
			cout << "Num Surfaces: " << md3header->num_surfaces <<endl;
			cout << "Num Skins: " << md3header->num_skins <<endl;
			cout << "Ofs Frames: " << md3header->ofs_frames <<endl;
			cout << "Ofs Tags: " << md3header->ofs_tags <<endl;
			cout << "Ofs Surfaces: " << md3header->ofs_surfaces <<endl;
			cout << "Ofs End: " << md3header->ofs_eof <<endl;

	for(int i=0; i<md3header->num_frames; i++)
	{
		cout << "Min Bounds: " << frames[i].min_bounds << endl;
		cout << "Max Bounds: " << frames[i].max_bounds << endl;
		cout << "Local Origin: " << frames[i].local_origin << endl;
		cout << "Radius: " << frames[i].radius << endl;
		cout << "Name: " << frames[i].name << endl;
	}

	for (int m=0; m<surfaces->num_triangles; m++)
	{
		cout << "1. " << triangles[m].indexes[0] <<endl;
		cout << "2. " << triangles[m].indexes[1] <<endl;
		cout << "3. " << triangles[m].indexes[2] <<endl;
	}

	this->num_triangles = surfaces->num_triangles;
		cout << surfaces->num_triangles << endl;

	for (int j=0; j<md3header->num_surfaces; j++)
	{
		cout << "Ident: " << surfaces[j].ident << endl;
		cout << "Name: " << surfaces[j].name <<endl;
		cout << "Flags: " << surfaces[j].flags <<endl;
		cout << "Num Frames: " << surfaces[j].num_frames <<endl;
		cout << "Num Shaders: " << surfaces[j].num_shaders <<endl;
		cout << "Num Vertices: " << surfaces[j].num_verts <<endl;
		cout << "Num Triangles: " << surfaces[j].num_triangles <<endl;
		cout << "Offset Triangles: " << surfaces[j].ofs_triangles <<endl;
		cout << "Offset Shaders: " << surfaces[j].ofs_shaders <<endl;
		cout << "Offset st: " << surfaces[j].ofs_st <<endl;
		cout << "Offset xyznormal: " << surfaces[j].ofs_xyznormal << endl;
		cout << "Offset End: " << surfaces[j].ofs_end <<endl;
	}
}

GameObject::~GameObject()
{
	//TODO: Some stuff
}


		void GameObject::draw() {

			cout << this->num_triangles << endl;
			glBegin(GL_TRIANGLES);
				for(int i=0; i<this->num_triangles;i++) {
						glVertex3f(this->triangles[i].indexes[0] /100000000,this->triangles[i].indexes[1] /100000000,this->triangles[i].indexes[2] /1000000000);
					}

					glEnd();
}

Any help to get this working would be extremely helpful. Also I'm not too sure on the "void GameObject::draw" part so help with that would be great too, but it had worked before so it's not so important.

[^misantropia^]

Any reason to use (c|m)alloc and array pointers instead of new and std::vector?

As to why it crashes... hard to tell. Load it in gdb and do a backtrace (`bt`) after the crash.

[Selphie142]

Right, I've found out that it's the reading in of the triangle data that is crashing the window. And the output out... Really not sure how to read this information in as the num_triangles is not within the md3_header... so I have to reference to the surface_header. I've changed this to:

Code: Select all

this->triangles = (md3_triangle_header *)
				calloc(this->num_triangles,sizeof(struct md3_surface_header));
			md3file.seekg(this->surfaces->ofs_triangles, ios::beg);
			md3file.read((char *)triangles,sizeof (struct md3_triangle_header)* surfaces->num_triangles);

This, once again is crashing the window applet. Also, I think it's wrong.

The rest all works and outputs the information correctly, so this is the only thing I'm stuck on right now and I would really appreciate help to get the program to read in the information (and obviously print out to check if it works :P).

[^misantropia^]

You mean this->num_triangles isn't initialized before you reference it?

[Selphie142]

I'm not too sure. I'm trying to read in the data as with the other parts (verts, tags, surfaces etc) but these are in the md3_header of the header file whereas the triangles is referenced in the surface_header.

Basically, I'm just not sure how to get the data for the triangles to be read in so that it can be displayed.

[^misantropia^]

I'm not too sure.

This is always the wrong answer when it comes to programming. :)

num_triangles is part of the surface header so step through your code with a debugger and make sure it is read correctly. BTW, what exactly do you mean when you say 'window applet'?

[garkwreri]

And what, if to us to look at this question from other point of view?