SSAO isn't working with model without normals

[Meakk]

Describe the bug
When there's no normals on the model, SSAO is not working properly

To Reproduce
Steps to reproduce the behavior:

1. Open a file without normals
2. Enable SSAO

Expected behavior
SSAO should work with generated flat normals

[Meakk]

Shader G-buffer output (last image is black but it should contain the normals)

Fragment output is set with:

fragOutput2 = vec4(normalVCVSOutput, 1.0);

But without normal, the shader contains:

    // Generate the normal if we are not passed in one
    vec3 primitiveNormal;
    if (primitiveSize == 1) {
        primitiveNormal = vec3(0.0, 0.0, 1.0);
    }
    else if (primitiveSize == 2) {
        float addOrSubtract = (dot(fdx, fdy) >= 0.0) ? 1.0 : -1.0;
        vec3 lineVec = addOrSubtract*fdy + fdx;
        primitiveNormal = normalize(cross(vec3(lineVec.y, -lineVec.x, 0.0), lineVec));
    }
    else {
        primitiveNormal = normalize(cross(fdx, fdy));
        if (cameraParallel == 1 && primitiveNormal.z < 0.0) {
            primitiveNormal = -1.0*primitiveNormal;
        }
        if (cameraParallel == 0 && dot(primitiveNormal, vertexVC.xyz) > 0.0) {
            primitiveNormal = -1.0*primitiveNormal;
        }

    }
    vec3 vertexNormalVCVS = primitiveNormal;
    vec3 normalizedNormalVCVSOutput = normalize(vertexNormalVCVS);

So I'd say we should do something like:

fragOutput2 = vec4(normalizedNormalVCVSOutput, 1.0);

[Meakk]

Fix in VTK: https://gitlab.kitware.com/vtk/vtk/-/merge_requests/11417

[Meakk]

Fixed by updating VTK in f3d-app/f3d-docker-images#18

[mwestphal]

So this was F3DWeb specific right ?