Learning C, Day 8 (Loading OBJ Files)

Today I spent about two and a half hours on the course and I got my renderer loading OBJ files! So I had to render the Blender Suzanne monkey:

I’m pretty sure my method of parsing OBJ files is awful, so I’ll probably rewrite it at some point. Here’s the code snippet:

int load_obj_file_data(char* filename) {
	// Load the vertices and faces to the mesh.vertices and mesh.faces arrays
	// For each line in file:
	// 		If line starts with "n", parse a vertex and add it to the list of vertices.
	// 		If the line starts with "f", parse a face and add it to the list of faces.
	FILE* fp = NULL;
	char buffer[60]; // Probably shouldn't hard code this.
	char* delimiter = " ";
	
	fp = fopen(filename, "r");
	
	if (fp == NULL) { // Exit if there's an error opening the file
		return 1;
	}
	// Read the file
	while (fgets(buffer, 60, fp) != NULL) {
		if (buffer[0] == 'v' && buffer[1] != 'n') { // Process a vertex.
			char* ptr = strtok(buffer, delimiter); // Advance the pointer once to skip the "i"
			vec3_t new_vertex;

			ptr = strtok(NULL, delimiter);
			new_vertex.x = strtof(ptr, NULL);
			ptr = strtok(NULL, delimiter);
			new_vertex.y = strtof(ptr, NULL);
			ptr = strtok(NULL, delimiter);
			new_vertex.z = strtof(ptr, NULL);
			array_push(mesh.vertices, new_vertex);
		} else if (buffer[0] == 'f') {              // Process a face.
			strtok(buffer, delimiter); // Advance the pointer once to skip the "f"
			char* ap;
			char* bp;
			char* cp;
			int a,b,c;
			face_t new_face;

			ap = strtok(NULL, delimiter);// Get pointers to each of the elements in the line
			bp = strtok(NULL, delimiter);
			cp = strtok(NULL, delimiter);

			a = strtol(strtok(ap, "/"), NULL, 10); // Get just the first number in each element and convert it to an integer.
			b = strtol(strtok(bp, "/"), NULL, 10);
			c = strtol(strtok(cp, "/"), NULL, 10);
			new_face.a = a;	// Populate the face with the new values.
			new_face.b = b;
			new_face.c = c;
			array_push(mesh.faces, new_face); // Push the new face onto the mesh faces array.
		}
	}

	fclose(fp);
	return 0;
}

I’ll see you tomorrow!