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Aitorman

OpenGL Simple obj loader for OpenGl

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Hello there,
I'm looking for a simple obj laoder for OpenGL, wich reads vertex,normal, index and uv data. Everything I've seen is either too simple (doesn't have support for index data), or too complex (assimp, for example). Doesn anyone know of a simple obj loader wich gets index data?

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I haven't been able to find one. I tried writing one myself which proved to be an exercise in futility. Assimp isn't incredibly difficult for simply loading models and once you get the wrapper done you can use any model type Assimp supports.

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I have "something" that I coded in 2004 when I was still a young newbie programmer. It's pure C (no classes) with french variable names and comments and probably very unstable and very badly coded (static array and such) but since I have it I'll paste it here. "Charger" is load, "Afficher" is draw.

[source lang="cpp"]struct point3D{
float X;
float Y;
float Z;
};

struct PointsAsso{
int pt1;
int pt2;
int pt3;
};

struct PointsTexture{
float X;
float Y;
};

struct Association{
PointsAsso ptModele;
PointsAsso ptTexture;
};

struct Modele{
point3D tabPointsModele[512];
PointsTexture tabPointsTexture[512];
Association tabAsso[512];
int nbAsso;
};

void M2500_CHARGER_MODELE(char *nomFichier,Modele *nomModel)
{
FILE *fichierModele;
fichierModele = fopen(nomFichier,"r");
char tempCar;
char tempChaine[255];
int i =0;
int j =0;
int k =0;
int longueur;

while (!feof(fichierModele))
{
tempCar = fgetc(fichierModele);
if(tempCar == 'v') //point d'un sommet
{
tempCar = fgetc(fichierModele);
if(tempCar == ' ')
{
fscanf(fichierModele,"%f %f %f",&nomModel->tabPointsModele.X,&nomModel->tabPointsModele.Y,&nomModel->tabPointsModele.Z);
i++;
}
if(tempCar == 't') //point d'une texture
{
tempCar = fgetc(fichierModele);
fscanf(fichierModele,"%f %f",&nomModel->tabPointsTexture[j].X,&nomModel->tabPointsTexture[j].Y);
j++;
}
}
if(tempCar == 'f') //face (association sommet/texture)
{
tempCar = fgetc(fichierModele);
fgets(tempChaine,255,fichierModele);
nomModel->nbAsso++;

//pt1 modele
nomModel->tabAsso[k].ptModele.pt1 = atoi(tempChaine);

//pt1 texture
longueur = M2510_OBTENIR_LONGUEUR_ENTIER(nomModel->tabAsso[k].ptModele.pt1);
strcpy(tempChaine, &tempChaine[longueur+1]);
nomModel->tabAsso[k].ptTexture.pt1 = atoi(tempChaine);

//pt2 modele
longueur = M2510_OBTENIR_LONGUEUR_ENTIER(nomModel->tabAsso[k].ptTexture.pt1);
strcpy(tempChaine, &tempChaine[longueur+2]);
nomModel->tabAsso[k].ptModele.pt2 = atoi(tempChaine);

//pt2 texture
longueur = M2510_OBTENIR_LONGUEUR_ENTIER(nomModel->tabAsso[k].ptModele.pt2);
strcpy(tempChaine, &tempChaine[longueur+1]);
nomModel->tabAsso[k].ptTexture.pt2 = atoi(tempChaine);

//pt3 modele
longueur = M2510_OBTENIR_LONGUEUR_ENTIER(nomModel->tabAsso[k].ptTexture.pt2);
strcpy(tempChaine, &tempChaine[longueur+2]);
nomModel->tabAsso[k].ptModele.pt3 = atoi(tempChaine);

//pt3 texture
longueur = M2510_OBTENIR_LONGUEUR_ENTIER(nomModel->tabAsso[k].ptModele.pt3);
strcpy(tempChaine, &tempChaine[longueur+1]);
nomModel->tabAsso[k].ptTexture.pt3 = atoi(tempChaine);

k++;
}
}
fclose(fichierModele);
}

int M2510_OBTENIR_LONGUEUR_ENTIER(int entier)
{
if (entier < 10)
return 1;
if (entier >= 10 && entier < 100)
return 2;
if (entier >= 100 && entier < 1000)
return 3;
if (entier >= 1000 && entier < 10000)
return 4;
else
return 0;
}

void M4240_AFFICHER_MODELE(float x,float y,float z, struct Modele *nomModel, int numTexture, float grosseur, bool rotation, float deltaT)
{
static float rot;
glPushMatrix(); //Conserve l'ancienne matrice
glTranslatef(x,y,z); //Bouge à la position de l'objet
rot+= deltaT*2; //Tourner par rapport au temps
glScalef(grosseur, grosseur, grosseur); //Change la grosseur (modèles pas sauvés tous pareil)

if(rotation)
glRotatef(rot,0,0,1);

if(numTexture != -1)
glBindTexture(GL_TEXTURE_2D, numTexture);
else
glBindTexture(GL_TEXTURE_2D, 0);

glBegin(GL_TRIANGLES);
for (int i = 0; i < nomModel->nbAsso; i++)
{
int AssoMod1 = nomModel->tabAsso.ptModele.pt1;
int AssoMod2 = nomModel->tabAsso.ptModele.pt2;
int AssoMod3 = nomModel->tabAsso.ptModele.pt3;
int AssoTex1 = nomModel->tabAsso.ptTexture.pt1;
int AssoTex2 = nomModel->tabAsso.ptTexture.pt2;
int AssoTex3 = nomModel->tabAsso.ptTexture.pt3;

glTexCoord2f( nomModel->tabPointsTexture[AssoTex1-1].X,
nomModel->tabPointsTexture[AssoTex1-1].Y);
glVertex3f( nomModel->tabPointsModele[AssoMod1-1].X,
nomModel->tabPointsModele[AssoMod1-1].Y,
nomModel->tabPointsModele[AssoMod1-1].Z);

glTexCoord2f( nomModel->tabPointsTexture[AssoTex2-1].X,
nomModel->tabPointsTexture[AssoTex2-1].Y);
glVertex3f( nomModel->tabPointsModele[AssoMod2-1].X,
nomModel->tabPointsModele[AssoMod2-1].Y,
nomModel->tabPointsModele[AssoMod2-1].Z);

glTexCoord2f( nomModel->tabPointsTexture[AssoTex3-1].X,
nomModel->tabPointsTexture[AssoTex3-1].Y);
glVertex3f( nomModel->tabPointsModele[AssoMod3-1].X,
nomModel->tabPointsModele[AssoMod3-1].Y,
nomModel->tabPointsModele[AssoMod3-1].Z);
}
glEnd();
glPopMatrix(); //Remet l'ancienne matrice
}
[/source] Edited by Dunge

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I've been using this guy's source code for it for literally years:
http://www.dhpoware.com/demos/glObjViewer.html
Have run it on various OpenGL and GL ES versions, and D3D versions, depending on the project. It's very flexible.

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