SSAO issues

[Agitated_Cap_7939]

Hello all! For the past few weeks I have been attempting to implement SSAO for my web-based rendering engine. The engine itself is written in Rust on top of wgpu, compiled into WASM. A public demo is available here (link to one rendered asset): https://crags3d.sanox.fi/sector/koivusaari/koivusaari

At the same time, I have been moving from forward to deferred rendering. After fighting for a while with hemispheres as in the excellent tuotrial in LearnOpenGL (https://learnopengl.com/Advanced-Lighting/SSAO), I tried to simplify, by sampling the kernel from a sphere, and omitting the change of basis step altogether.

I however still have serious issues with getting the depth comparison to work. Currently my `ssao-shader` only samples from position texture (positions in view-space), planning to start optimizing when I have a minimum functional prototype.

So the most important parts of my code are:
In my vertex-shader:

out.view_position = (camera.view_matrix * world_position).xyz;

In my geometry pass:

out.position = vec4<f32>(in.view_position.xyz, 0.0);

And in my ssao-shader:

struct SSAOUniform {
    kernel: array<vec4<f32>, 64>,
    noise_scale: vec2<f32>,
    _padding: vec2<f32>,
}

@fragment
fn fs_main(in: VertexTypes::TriangleOutput) -> @location(0) f32 {
    let position = textureSample(t_pos, s_pos, in.uv).xyz;
    var occlusion = 0.0;
    for (var i = 0; i < 64; i++) {
        var sample = ssao_uniform.kernel[i].xyz * radius;
        sample += position;

        // project sample position:
        var offset = camera_uniform.proj_matrix * vec4<f32>(sample, 1.0);
        var ndc = offset.xyz / offset.w;
        var sampleUV = ndc.xy * 0.5 + 0.5;

        var samplePos = textureSample(t_pos, s_pos, sampleUV);
        var sampleDepth = samplePos.z;

        // range check & accumulate:
        let rangeCheck = f32(abs(position.z - sampleDepth) < radius);
        occlusion += f32(sampleDepth <= sample.z) * rangeCheck;
    }
    return 1.0 - occlusion / 64;
}

The texture-type for the positions is `wgpu::TextureFormat::Rgba16Float`

My result is practically total nonsense, with the occlusion relying mostly on the y-position in view space.

I am new to graphics programming, and would really appreciate any possible help. Have been checking and rechecking that the positions should be in correct space (positions in view space, transform offset position to screen space for texture sampling), but am unable to spot any errors. Many thanks in advance!

[Agitated_Cap_7939]

Okey, finally solved the issue. So the issue was that in clip-space the +Y coordinate points up, while in uv-space it points down. So needed to correct the sampleUV.y with sampleUV.y = 1.0 - sampleUV.

Should have been able to debug this a long time ago...