Crash when I try to render a triangle mesh (c++)

Question

I'm trying to render a triangle mesh with Phong shading using GLSL, here is my method to assign normals.

void renderWireframe(Mesh *mesh) 
{
    glDepthMask(GL_TRUE);
    glBegin(GL_TRIANGLES);
    for(int i=0; i<mesh->nt; i++) { //nv is the mesh's number of triangles

    int i0 = mesh->triangles[i].vInds[0];
    int i1 = mesh->triangles[i].vInds[1];
    int i2 = mesh->triangles[i].vInds[2];

    //Calculate normals for each vertex
    Vector fv0 = getvertexnormal(mesh, i0);
    Vector fv1 = getvertexnormal(mesh, i1);
    Vector fv2 = getvertexnormal(mesh, i2);

    glNormal3dv((double *)&fv0);
    glVertex3dv((double *)&mesh->vertices[i0]);
    glNormal3dv((double *)&fv1);
    glVertex3dv((double *)&mesh->vertices[i1]);
    glNormal3dv((double *)&fv2);
    glVertex3dv((double *)&mesh->vertices[i2]);
    }
glEnd();
}

The getvertexnormal code looks like this:

Vector getvertexnormal(Mesh *mesh, int vertex){
    int i = mesh->nt; //nt is the mesh's number of triangles
    int *adjface;
    adjface = new int[i]; //array to store adjacent faces

    //Store each triangle which has an intersection with the vertex'th vertex
    int nadjface = 0; 
    Triangle *t = mesh->triangles;
    for (int ix = 0; ix < mesh->nt; ix++){
        if(t[ix].vInds[0] == vertex){
            adjface[nadjface++] = ix;
        }
        else
            if (t[ix].vInds[1] == vertex)
                adjface[nadjface++] = ix;
            else
                if (t[ix].vInds[2] == vertex)
                    adjface[nadjface++] = ix;
    }

    // Average all adjacent triangles normals to get the vertex normal
    Vector norm = {0.0, 0.0, 0.0};
    for (int jx = 0; jx < nadjface; jx++){
        int ixFace = adjface[jx];
        norm.x += mesh->triangles[ixFace].vInds[0];
        norm.y += mesh->triangles[ixFace].vInds[1];
        norm.z += mesh->triangles[ixFace].vInds[2];
    }
    norm.x /= nadjface;
    norm.y /= nadjface;
    norm.z /= nadjface;
    return Normalize(norm);
}

Everytime I run this it looks like it starts rendering and then after one second it crashes and gives me an exception:

"Unhandled exception at at 0x7562B727 in glutglsl.exe: Microsoft C++ exception: std::bad_alloc at memory location 0x0028F1C8."

The program works fine if I comment out the getvertexnomral() parts and instead of

glNormal3dv((double *)&fv0);
glVertex3dv((double *)&mesh->vertices[i0]);
glNormal3dv((double *)&fv1);
glVertex3dv((double *)&mesh->vertices[i1]);
glNormal3dv((double *)&fv2);
glVertex3dv((double *)&mesh->vertices[i2]);

I write

glNormal3dv((double *)&Normalize(mesh->vertices[i0]));
glVertex3dv((double *)&mesh->vertices[i2]);
glNormal3dv((double *)&Normalize(mesh->vertices[i1]));
glVertex3dv((double *)&mesh->vertices[i1]);
glNormal3dv((double *)&Normalize(mesh->vertices[i2]));
glVertex3dv((double *)&mesh->vertices[i2]);

but then it doesn't look right (https://i.stack.imgur.com/eJthY.jpg)

so I'm thinking there's a problem with getvertexnormal().

By the way I'm a complete novice at this stuff. I have all my phong calculation in my fragment shader (GLSL). To achieve phong shading on a large triangle mesh this is the way to go right?

`std::bad_alloc` means you are out of memory. what is the value of `mesh->nt` ? — Elazar, Jun 27 '13 at 13:09

Elazar · Answer 1 · 2013-06-27T14:12:12.640

Your problem is a memory leak.

You are allocating memory

adjface = new int[i];

But you never delete it. The value returned from new is stored in a local variable, and never copied anywhere, nor being returned from the function. So what you have is a memory leak, which lead to memory exhaustion and allocation error - so new throws std::bad_alloc.

This is C++. Don't use arrays; use std::vector instead. Or delete[] it.

But I think you don't really need an array here:

Vector getvertexnormal(Mesh *mesh, int vertex) {
    int nadjface = 0; 
    Triangle *t = mesh->triangles;
    Triangle *last = t + (mesh->nt - 1);
    Vector norm = {0.0, 0.0, 0.0};
    for (; t <= last; t++) {
        for (int i = 0; i < 3; i++) {
            if (t->vInds[i] == vertex) {
                nadjface++;
                norm.x += t->vInds[0];
                norm.y += t->vInds[1];
                norm.z += t->vInds[2];
                break;
            }
        }
    }
    return Normalize(norm / nadjface);
}

And if I am not mistaken, you can simply do

norm += t->vInds;

or domething like that. It can make you code shorter, more readable, and probably even faster.

Thanks a lot, been a long time C# user and fairly new to C++ so that's probably the reason. — user2527567, Jun 27 '13 at 15:18

Crash when I try to render a triangle mesh (c++)

1 Answers1