Setting up OpenGL shaders with QGLWidget

The title isn't really the question, but it's the best I could do to summarize my problem.

I have a Qt program with a child of QGLWidget and everything is working just fine with OpenGL 3.3. The one problem I'm getting is that all the meshes I create are transparent even though their alpha values are set to 1 (remembering that OpenGL works on 0-1, not 0-255). I've played around with the OpenGL commands but can't get it to work. This all sounds and feels like its more of an OpenGL problem than a Qt problem, but I'm not being able to get much help from the people at the opengl.org forums and so, thinking that maybe I was missing something Qt-related, I returned to the documentation and found the following.

In the QGLWidget docs, there's a little example of how a child should look like, and it contains:

Code:

---

glEnable(GL_DEPTH_TEST);

---

However, the QGLFormat::depth() docs say that depth-testing is active by default. So why does QGLWidget enable it?

In any case, here is my code attempting to set these things up.

Code:

---

//fragment shader
#version 330
precision highp float;
 
uniform vec3 EyeAxis = vec3(0.0,0.0,1.0);
uniform mat4 Modelview;
uniform mat4 Projection;
in vec3 ex_Color;
in vec4 ex_Normal;
out vec4 FragColor;
 
void main(void)
{
	vec4 Normal = Projection*Modelview*ex_Normal;
	vec4 Eye = vec4(EyeAxis,1.0);
	float c = abs(dot(normalize(Eye.xyz),normalize(Normal.xyz)));
	FragColor = vec4((0.2+0.8*c)*ex_Color,1.0);
}

---

Code:

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void MyNGLWidget::Initialize()
{
	//only called after drawing data (coordinates, colors, normals, etc) have been loaded
	GenBuffers();
	GenShaders();
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
	glEnable(GL_DEPTH_TEST);
 
	Initialized = true;
	updateGL();
}
void MyNGLWidget::initializeGL()
{
	glewInit();
	format().setDepth(true); //even though its true by default
	format().setDepthBufferSize(32); //even though Qt tends to reject this value and stick to 24X8
}

---

Any hints and tips?

Isn't it the fault of GL_BLEND? What if you disable it?

Unfortunately, I started playing (and thus enabled) with glBlend precisely because of this problem...

Ah, and yeah, I forgot to add that I also have

Code:

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glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

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in every paint call.

This seems to be purely OpenGL issue. Start disabling things until everything starts working. At least you'll know where to look.

Quote:

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(...) thinking that maybe I was missing something Qt-related

---

So create an OpenGL app without Qt, this way you will know if this issue is related to Qt.
What does it look like if you disable shaders (and GL_BLEND, as wysota mentioned) ?

I actually started with an OpenGL app without Qt (using glut and such things) and then transferred it into Qt. I didn't notice the transparency before, but it's quite possible I simply didn't notice it. Hell, I've been working on this Qt version for a while and only noticed it now (I'm currently only working with one object, so I have to get just the right angles to be able to see the object through itself).

And I can't disable the shaders since I would then have to rewrite the entire code to work with glBegin()/glEnd() instead of the method I'm using now, but without GL_BLEND, it doesn't really change much. But I'm also pretty sure this is OpenGL related, so I'll just go ask on their forums.

Thanks for the help.

I think the orientation of the faces might be wrong. Just use: glFrontFace(GL_CW);

setDepth(true) enables the *depth buffer* in the context and does nothing for depth testing.
try add glDepthFunc(GL_LEQUAL); somewhere in your initialization.

also, the QGLFormat need to be setup before you create the context, and then sent in to the constructor as the second parameter.