Newbie`s question with using lib3ds in OpenGL programs.

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Hi there!

I am currently using lib3ds draw models in my opengl program.

After drawing vertex reading from the 3ds file, it appears a vehicle model on screen, but while I assign the light onto the surface I found there is some fragment displayed incorrectly.

Some far pixel appeared on the nearer surface (matter fact I enabled the depth buffer facility) that I can`t figure what`s wrong with the code.

Attached is my code:

C#

#include <windows.h>
#include <gl/gl.h>
#include <gl/glu.h>
#include <gl/glut.h>
#include <lib3ds.h>
#include <iostream>
typedef float Lib3dsVector[3];
typedef float Lib3dsTexel[2];
using namespace std;
Lib3dsFile* model;
Lib3dsMesh** mesh;
Lib3dsCamera** camera;
Lib3dsFace* face;
Lib3dsLight** light;
Lib3dsMaterial** material;
GLuint vertexVBO,normalVBO,textureVBO;
unsigned long total_face;
void lightup()
{
    glShadeModel(GL_SMOOTH);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);
    glFrontFace(GL_CCW);
    float gambient[]={0.2,0.2,0.2,1.0};
    float lightpos[]={1.0,1.0,1.0,0.0};
    float lambient[]={1.0,1.0,1.0,1.0};
    float ldiffuse[]={0.8,0.8,0.8,1.0};
    float lspecular[]={0.3,0.3,0.3,1.0};
    glLightfv(GL_LIGHT0,GL_DIFFUSE,ldiffuse);
    glLightfv(GL_LIGHT0,GL_AMBIENT,lambient);
    glLightfv(GL_LIGHT0,GL_SPECULAR,lspecular);
    glLightfv(GL_LIGHT0,GL_POSITION,lightpos);
    glLightModelfv(GL_LIGHT_MODEL_AMBIENT,gambient);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
}
void getfaces()
{
    total_face=0;
    for(long meshcount=0;meshcount<model->nmeshes;meshcount++)
        total_face+=mesh[meshcount]->nfaces;
}
void display()
{
    glEnable(GL_DEPTH_TEST);
    glClearDepth(1.0);
    glDepthFunc(GL_LEQUAL);
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BITS);
    glLoadIdentity();
    gluLookAt(camera[0]->position[0]+1000,camera[0]->position[1],camera[0]->position[2],camera[0]->target[0],camera[0]->target[1],camera[0]->target[2],0.0,0.0,1.0);
    glColor3f(1.0,0.0,0.0);
    glPushMatrix();
    lightup();
    glScalef(0.5,0.5,0.5);
    glTranslatef(0.0,0.0,-1000.0);
    long meshcount;
    for(meshcount=0;meshcount<model->nmeshes;meshcount++)
    {
        face=mesh[meshcount]->faces;
        for(long i=0;i<mesh[meshcount]->nfaces;i++)
        {
            glMaterialfv(GL_FRONT,GL_DIFFUSE,material[face[i].material]->diffuse);
            glMaterialfv(GL_FRONT,GL_AMBIENT,material[face[i].material]->ambient);
            glMaterialfv(GL_FRONT,GL_SPECULAR,material[face[i].material]->specular);
            glBegin(GL_TRIANGLES);
            glVertex3fv(mesh[meshcount]->vertices[face[i].index[0]]);
            glVertex3fv(mesh[meshcount]->vertices[face[i].index[1]]);
            glVertex3fv(mesh[meshcount]->vertices[face[i].index[2]]);
            glEnd();
        }
    }
    glPopMatrix();
/*
    glPushMatrix();
    glTranslatef(0.0,0.0,-2000.0);
    glColor3f(1.0,1.0,1.0);
    glBegin(GL_QUADS);
    glVertex3f(-10000.0f,-10000.0f,0.0f);
    glVertex3f(10000.0f,-10000.0f,0.0f);
    glVertex3f(10000.0f,10000.0f,0.0f);
    glVertex3f(-10000.0f,10000.0f,0.0f);
    glEnd();
    glPopMatrix();
*/
    glutSwapBuffers();
}
void keypress(unsigned char key,int x,int y)
{
    switch(key)
    {
    case 27:
        exit(0);
        break;
    }
}
void reshape(int w,int h)
{
    if(h==0) h=1;
    glViewport(0,0,w,h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0,w/h,0.0,1000.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}
int main(int argc,char* argv[])
{
    glutInit(&argc,argv);
    model=lib3ds_file_open("vehicle.3DS");
    if(model==NULL) cout<<"Error"<<endl; else cout<<model->nmaterials<<endl;
    mesh=model->meshes;
    material=model->materials;
    camera=model->cameras;
    light=model->lights;
    cout<<"Light Num:"<<model->nlights<<endl;

    glutInitDisplayMode(GLUT_RGB|GLUT_DOUBLE|GLUT_DEPTH);
    glutInitWindowSize(800,800);
    glutInitWindowPosition(100,100);
    glutCreateWindow("VC 2008 Glut");
    //glutFullScreen();
    glShadeModel(GL_FLAT);
    glutKeyboardFunc(keypress);
    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutMainLoop();
    return 0;
}

Thank you for reading, any answer would be appreciated.

Posted 19-Jan-11 20:32pm

JerryLin88

Updated 19-Jan-11 21:38pm

Dalek Dave

v2

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Dalek Dave 20-Jan-11 3:39am

Edited for Grammar, Syntax and Readability.

GPUToaster™ 20-Jan-11 3:56am

Provide a screen shot so that it will help members to identify problem and reply promptly.

revaldo666 20-Jul-12 10:18am

how load 2 or more models to scene

2 solutions

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GPUToaster™ · Answer 1 · 2011-01-19T22:32:00

Solution 1

Try to use glDisable(GL_CULL_FACE), if it renders properly then some problem with the model itself, hopefully the normals.

If that is the case use glNormals*(). Let me know if you hit anything.

Posted 19-Jan-11 22:32pm

GPUToaster™

v2

Comments

JerryLin88 20-Jan-11 7:53am

thanx for your answer but glDisable(GL_CULL_FACE) doesn`t work,i guess as you mentioned perhaps the problem is caused by undefined normals of each face.after i defined the vertex normal it looks much better than before but some fragments are still broken,when i refer to the normal calculation i read some lines of the lib3ds header files.and i got 2 method for normal calculation.1 for vertex and another for face.i just used vertex normal but i have no idea how to use face normal.anyway your advise helps me alot.thank you

GPUToaster™ 20-Jan-11 8:28am

I never used lib3ds. I can only say probable causes. So i guess you have answered your own query, thats remarkable!
And i'l try to follow what you have here.

JerryLin88 20-Jan-11 9:40am

i am just not sure whether it will render properly after applying face normals as titled i am just a newbie to opengl and i ve no idea dealing with face normal combined with vertex normals and the normalize operation costs too much resource withing slow down my program extremely so do u have any optimization suggestion? thanx for your time looking forwards to your reply.

GPUToaster™ 20-Jan-11 13:00pm

I'm not an optimization master...but you might want to refer to some common OpenGL pitfalls.
Here you go: http://www.opengl.org/resources/features/KilgardTechniques/oglpitfall/

Hope it helps! Best luck.

JerryLin88 · Answer 2 · 2011-01-20T01:56:00

C#

for(meshcount=0;meshcount<model->nmeshes;meshcount++)
{
    face=mesh[meshcount]->faces;
    Lib3dsVector* vertex_normal=new Lib3dsVector[mesh[meshcount]->nfaces*3];
    lib3ds_mesh_calculate_vertex_normals(mesh[meshcount],vertex_normal);
    for(long i=0;i<mesh[meshcount]->nfaces;i++)
    {
        glMaterialfv(GL_FRONT,GL_DIFFUSE,material[face[i].material]->diffuse);
        glMaterialfv(GL_FRONT,GL_AMBIENT,material[face[i].material]->ambient);
        glMaterialfv(GL_FRONT,GL_SPECULAR,material[face[i].material]->specular);
        glBegin(GL_TRIANGLES);
        glNormal3fv(vertex_normal[i*3]);
        glVertex3fv(mesh[meshcount]->vertices[face[i].index[0]]);
        glNormal3fv(vertex_normal[i*3+1]);
        glVertex3fv(mesh[meshcount]->vertices[face[i].index[1]]);
        glNormal3fv(vertex_normal[i*3+2]);
        glVertex3fv(mesh[meshcount]->vertices[face[i].index[2]]);
        glEnd();
    }
}

here is my modified source code.as u can see lib3ds_mesh_calculate_vertex_normals for vertex and lib3ds_mesh_calculate_face_normals for face.