Misaligned/askew textures?

I have written an OBJ/MTL parser and I’m trying to render an object.

The problem is that some textures are misaligned/askew and I have no idea why. On some textures it seems fine, however on others, it does not – it looks as if the texture coordinates are outside the [0, 1] range, which I’m told is fine, as in some cases it should do clamp/wrap; however it seems as if this takes place when it shouldn’t.

I have verified that the data contained in my data structures is correct as loaded from the OBJ and MTL file.

I have verified that the OBJ file can be rendered without the artifacts I see in my program – I used dhpoware’s renderer for this.

EDIT: Of interest is perhaps that all textures are not only upside down (which I why I use the negative u and v values to correct for this) but also laterally reversed – i.e. mirrored. Could this be part of the solution to why I’m getting the other problems with the textures being askew and misaligned?

	for(int i = 0; i < obj_data1.num_faces; i++) {
		if(mtl_data1.textures[obj_data1.faces[i]->material_index]->hasTexture) {
			glBindTexture(GL_TEXTURE_2D, mtl_data1.textures[obj_data1.faces[i]->material_index]->texture_ID[0]);
			textures_enabled = 1;
		else {
			if(textures_enabled) {
				textures_enabled = 0;

		if(wrld.model_lighting) {
			glMaterialfv(GL_FRONT, GL_AMBIENT, mtl_data1.textures[obj_data1.faces[i]->material_index]->Ka);
			glMaterialfv(GL_FRONT, GL_DIFFUSE, mtl_data1.textures[obj_data1.faces[i]->material_index]->Kd);
			glMaterialfv(GL_FRONT, GL_SPECULAR, mtl_data1.textures[obj_data1.faces[i]->material_index]->Ks);


		for(int j = 0; j < obj_data1.faces[i]->length; j += 3) {
			glNormal3f(obj_data1.normals[obj_data1.faces[i]->indices[j + 2] - 1].x, obj_data1.normals[obj_data1.faces[i]->indices[j + 2] - 1].y, obj_data1.normals[obj_data1.faces[i]->indices[j + 2] - 1].z);
			if(mtl_data1.textures[obj_data1.faces[i]->material_index]->hasTexture) {
				glTexCoord2f(-obj_data1.texture_coordinates[obj_data1.faces[i]->indices[j + 1] - 1].u, -obj_data1.texture_coordinates[obj_data1.faces[i]->indices[j + 1] - 1].v);
			glVertex3f(obj_data1.vertices[obj_data1.faces[i]->indices[j] - 1].x, obj_data1.vertices[obj_data1.faces[i]->indices[j] - 1].y, obj_data1.vertices[obj_data1.faces[i]->indices[j] - 1].z);


Does this approach seem to be the right idea? Am I missing something crucial and simple?

If it helps, my structs are:

struct vector {
	double x;
	double y;
	double z;

struct vertex {
	double x;
	double y;
	double z;

struct texture_coordinate {
	double u;
	double v;

struct texture {
	int width;
	int height;
	char filename[MAX_FILENAME_LENGTH];
	float Ka[4]; // Ambient
	float Kd[4]; // Diffuse
	float Ks[4]; // Specular
	unsigned int texture_ID[1];
	_Bool hasTexture;

struct face {
	int *indices;
	int length;
	int material_index;
	struct texture text;

struct objdata {
	int num_vertices;
	struct vertex *vertices;

	int num_normals;
	struct vector *normals;

	int num_texture_coordinates;
	struct texture_coordinate *texture_coordinates;
	double max_vt;
	double min_vt;

	int num_faces;
	struct face **faces;

	float translation_x;
	float translation_y;
	float translation_z;

	float rotations_x;
	float rotations_y;
	float rotations_z;

struct mtldata {
	int num_textures;
	int index;
	struct texture **textures;

Looks like problem with GL_TEXTURE_WRAP parameter.
did you set any Texture parameters with glTextureParameter ?(I don’t see any calls in Your code)
look at this:
(close to half of the page)

I do not know OBJ format, but I’ve seen problems with mirrored textures somewhere else
(maybe OBJ format specifies coordinates from another corner than OpenGL?)