I'm having a weird problem with alpha: I have a tree model with a PNG texture that has transparency between its leafs and a floor (just GL_QUADS) with a JPG grass texture. I can see the floor through the tree, but I can't see a tree through another, it's just black instead of transparency. Here is my init code:

glEnable(GL_TEXTURE_2D);
glShadeModel(GL_SMOOTH);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClearDepth(1.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

And here is the loop:

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();

glPushMatrix();
glBindTexture(GL_TEXTURE_2D, m_tex_grass);
for (int x = 0; x < 6; x++) {
    for (int y = 0; y < 20; y++) {
	glPushMatrix();

	glTranslatef(-9.0f + (x * 4.0f), -10.0f + (y * 4.0f), 0.0f);

	glBegin(GL_QUADS);
	glTexCoord2f(0.0f, 0.0f);
	glVertex3f(-2.0f, -2.0f, 0.0f);
	glTexCoord2f(0.0f, 1.0f);
	glVertex3f(-2.0f, 2.0f, 0.0f);
	glTexCoord2f(1.0f, 1.0f);
	glVertex3f(2.0f, 2.0f, 0.0f);
	glTexCoord2f(1.0f, 0.0f);
	glVertex3f(2.0f, -2.0f, 0.0f);
	glEnd();

	glPopMatrix();
    }
}
glPopMatrix();

for (int i = 0; i < 10; i++) {
    glBindTexture(GL_TEXTURE_2D, m_tex_tree);
    glPushMatrix();
    glTranslatef(-5.0f - ((i % 2) * 2), 10.0f + (i * 2), 0.0f);
    m_cgm_tree.draw();
    glPopMatrix();
}

for (int i = 0; i < 10; i++) {
    glBindTexture(GL_TEXTURE_2D, m_tex_tree);
    glPushMatrix();
    glTranslatef(5.0f + ((i % 2) * 2), 10.0f + (i * 2), 0.0f);
    m_cgm_tree.draw();
    glPopMatrix();
}

this code: m_cgm_tree.draw(); call this code:

if (m_vertIDs.size() == 4) {
    glBegin(GL_QUADS);
} else {
    glBegin(GL_TRIANGLES);
}
for (int i = 0; i < m_vertIDs.size(); i++) {
    if (hasUVTex())
	glTexCoord2f(m_vertUVs.x(), m_vertUVs.y());
    Vert vert = vertList[m_vertIDs];
    glNormal3f(vert.no().x(), vert.no().y(), vert.no().z());
    glVertex3f(vert.co().x(), vert.co().y(), vert.co().z());
}
glEnd();

For every face on the model. The only difference between the model and the floor, is I'm adding glNormal3f to the model. Please help me with this one. Thanks! PS: The leafs of the tree model are like thin blocks instead of planes, I did that to get correct light shading (So the leafs have 2 normals, one for every face). In case it matters. PS2: [Edited by - wagner_fsoares on December 27, 2009 3:28:25 PM]

I can't believe it was just the order!
Thanks man!
As for sorting, it won't be a problem because I'm using Qt and it has great List classes and Sorting methods.