glDrawArray is not working - ios

Question

I want to make some changes to an image using OpenGL.
So after loading the image, I prepare the texture and I put the following code.But The image didn't change to a triangle.
What am I doing wrong ?
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
static const Vertex3D vertices[] = {
{-1.0, 1.0, -0.0},
{ 1.0, 1.0, -0.0},
{ 0.0, -1.0, -0.0},
};
static const Vector3D normals[] = {
{0.0, 0.0, 1.0},
{0.0, 0.0, 1.0},
{0.0, 0.0, 1.0},
};
static const GLfloat texCoords[] = {
0.0, 1.0,
1.0, 0.0,
0.0, 0.0,
};
glLoadIdentity();
glTranslatef(0.0, 0.0, -3.0);
glBindTexture(GL_TEXTURE_2D, texture[0]);
glVertexPointer(3, GL_FLOAT, 3, vertices);
glNormalPointer(GL_FLOAT, 0, normals);
glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
//initiate the drawing process, we want a triangle, start at index 0 and draw 3 vertices
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_NORMAL_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);`

Answer 1

I am surprised by your glVertexPointer(3, GL_FLOAT, 3, vertices); the second 3 indicates the stride (a kind of spacing between the numbers)... I think it should be 0 instead of 3.
glVertexPointer(3, GL_FLOAT, 0, vertices);
Actually, do you see a triangle or nothing at all ?
Good luck!
Pierre
Ok: I tried your code, so I can say :
1) you shall put glVertexPointer(3, GL_FLOAT, 0, vertices); stride of 0 instead of 3, does clearly not work with 3 (even useless to check it) : there is no gap between your values.
2) it may come from your initialisation of the view (common problem): how do you setup the projection and modelview matrices? For instance, to see the triangle, I have to put
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0, 1.0, 1.0, 10.0); // field of view=45°, zNear..zFar = 1 to 10
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0, 0, -3.0);
i.e. don't forget to tell which matrix you wish to set before doing it, and setup the pojection properly: zNear <= min(your vertices.z), zFar >= max(your vertices.z) (Oooo it is over now, with OpenGL 4, no more implicit matrices)
I wish you find the bug.
Cheers