Fix Ogre2DepthCamera on macOS (Fortress)

[darksylinc]

🦟 Bug fix

Fixes #332 (again) for macOS and possibly any OS/HW/Driver combination.
Fixes #369

Summary

For a very long time macOS (and possibly other OS/HW/Driver combination) would fail the tests because the shader code was doing (simplified, in C to convey the explanation):

uint32_t valueToStore = r << 24 | g << 16 | b << 8 | a;
float output;
output = (float*)&valueToStore;
return output;

In ticket #332 I made a deep analysis and found out that given the wrong conditions, the bit pattern would result in either a denormal or a NaN in floating point; which risks being flushed to 0 (or set all types of NaN to the same type bit pattern of NaN).

Although the ticket was closed and tagged as "fixed", on some OS/HW/Driver combinations (e.g. macOS + Metal) this error would reappear.

This isn't just a mere test failure. This is an actual bug. Running DepthCamera in macOS could result in wrong readings.

This PR fixes the problem for good by using RGBA32_UINT instead of RGBA32_FLOAT; and having uints be reinterpreted to floats and back when needed; which is well-defined and much more stable as far as GPU shader compilers go.

The same fix is also part of PR #785 which targets Garden and includes other changes.

This PR is a backport specific for Fortress.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

Merging #797 (1bf08df) into ign-rendering6 (ceec441) will not change coverage.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           ign-rendering6     #797   +/-   ##
===============================================
  Coverage           77.83%   77.83%           
===============================================
  Files                 146      146           
  Lines               13416    13416           
===============================================
  Hits                10442    10442           
  Misses               2974     2974           

Impacted Files	Coverage Δ
ogre2/src/Ogre2DepthCamera.cc	88.37% <ø> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.