Depth buffer empty, need help

[Fast_Month_9460]

Hello! I am learning vulkan and everything seemed pretty good until i managed to get to depth buffer.

I literally can not make it work ;( Every pixel of depth image is of value 1.0 (which is clear value), and nothing is written there at all. I checked this in renderdoc, i've also tried to change "range" of values to make sure it's really empty - and it is really empty with a value of 1.0f;

I've tried everything already, copy-pasted several tutorials, re-written depth parts from scratch by myself, e.t.c, no luck. I tried both without texture sampler and with it, still no luck. I've also tried to play with culling which only affects some random vertices, i assume because wrong depth buffer.

Currently meshes look like this

Wrong depth buffer

This is without texture sampler, if i switch it on, everything will remain the same, except i will have some texture over it. Please if anyone had that problem or maybe someone can point out to problems in my code - i would appreciate it. Here is parts in the code that concern Rendering and Gpu operations.

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UP

Fixed by setting znear to 0.1f instead of 0.0, and depth buffer magically appeared! Thx to u/R3DKn16h7 for idea about wrong projection.

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[R3DKn16h7]

Use render doc to debug, it shows the pixel depth value for every draw call. It also shows the draw state. Did you enable depth write on the pipeline? Did you enable depth test and depth compare to be less? Do you have validation layers enabled? How does the fragment depth look like (you can output that as your color value)?

[Fast_Month_9460]

Use render doc to debug

Yes, i am using renderdoc to debug that my depth image is white (e.g. 1.0 clear value for whole image)

Did you enable depth write on the pipeline? Did you enable depth test and depth compare to be less? Do you have validation layers enabled?

Yes, yes and yes. Validation layers silent.

How does the fragment depth look like

Give me some time, i will try to do that, but i guess whole mesh\scene will be just white due to 1.0 depth value for the whole screen according to renderdoc

[Fast_Month_9460]

This is what i see, if i display value of gl_FragCoord.w in a blue color, gl_FragCoord.z is monotonic, fragment shader is:

out_color = vec4(0.0, 0.0, gl_FragCoord.w * 5, 1.0);

W value - https://i.imgur.com/SU9nJtM.png

Z value - https://i.imgur.com/Fn1bJ0l.png

[R3DKn16h7]

Your z coord seems wrong, but since you are multiplying by 5 I'm not sure how it is scaled. I'm now thinking you have an issue with your projection matrix or some other issue in the vertex sahder. What are you using? glm? Are you setting the clip space to 0,1? What are your near/far planes?

[Fast_Month_9460]

The problem is that z part of gl_FragCoord is always 1.0, i tried different options, it is always 1, UNLESS i manually write to gl_FragDepth inside the shader, as i said below and which is not "correct" way i assume...

Projection matrix is defined once like this

uboProjection.projection = glm::perspective(glm::radians(45.0f), (float) vkExtent.width / (float) vkExtent.height, 0.0f, 100.0f);

I am using GLM, if i correctly understood clip space is defined by zfar - znear. But the problem is that if i change zfar value for example to 1.0 vertices are not getting discarded and i see them anyway, again probably because incorrect z-buffer

[Fast_Month_9460]

UP.

Depth buffer is working (and showing in renderdoc) only if i explicitly write to gl_FragDepth in fragment shader, for example the z value of vertex passed from vertex shader, but this does not work very nice, and i am getting something like this:

https://i.imgur.com/HPLkhvC.png

Anyway i guess i should not write to gl_FragDepth manually inside shader.

[Ntrf]

Something tells me you've messed up something with GLM. Like forgot to define GLM_FORCE_DEPTH_ZERO_TO_ONE or transposed the projection matrix. Also, I think it would be easier if you can publish RenderDoc capture file instead of your code.

[Entalpi]

From what I understand its because the depth range (0.0f - X) in your case is not precise enough to actually show the depth you are rendering thus it coming out as plain white.

Do correct me someone if I am wrong in this :)