Transition to TGS Soft impulse solver

[fallenatlas]

Description

Oh boy...

Transition from XPBD solver to TGS solver.

Much of the solver for the penetration constraints was changed, we now make corrections based on impulses, based mainly on the equations for conservation of momentum with some bias proportional to the penetration which will work to separate the particles.

Collisions also work as soft constraints now, the values might need some tweaking in the future but they seem ok for now.

The integration also had to be changed and is now under the solver, because it just makes more sense.

The new loop is as follows:

• fixed step
  • collision stuff (unchanged)
  • prepare constraints (for now just create the penetration constraint for colliding pairs)
  • fixed substep
  • integrate velocity
  • solve velocity with bias
  • integrate position
  • solve velocity without bias (relax)
  • finalize position (apply position correction)

Currently the impulses are enough only to separate the particles, this means that some collisions may not look as expected because everything is perfectly inelastic. Elastic and inelastic collisions will come with restitution which should be the next PR.

Also of note that stacks of more than 2 particles aren't very good yet, so the complex physics sample won't look the best.

Checklist

• [x] Self-review changes.
• [x] Evaluate impact on the documentation.
• [x] Add entry to the changelog's unreleased section.

[github-actions[bot]]

PR Preview Action v1.4.7 :---: :rocket: Deployed preview to https://GameDevTecnico.github.io/cubos/docs-preview/pr-1273/ on branch gh-pages at 2024-06-30 13:49 UTC

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 145 lines in your changes missing coverage. Please review.

Project coverage is 40.54%. Comparing base (8627172) to head (2bf3064).

Files	Patch %	Lines
...c/physics/solver/penetration_constraint/plugin.cpp	0.00%	66 Missing :warning:
engine/src/physics/solver/integration/plugin.cpp	0.00%	54 Missing :warning:
engine/src/physics/solver/plugin.cpp	0.00%	16 Missing :warning:
...src/physics/constraints/penetration_constraint.cpp	0.00%	4 Missing :warning:
engine/src/physics/plugin.cpp	0.00%	3 Missing :warning:
engine/src/defaults/plugin.cpp	0.00%	1 Missing :warning:
engine/src/physics/fixed_substep/plugin.cpp	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1273 +/- ## ========================================== - Coverage 40.58% 40.54% -0.04% ========================================== Files 359 359 Lines 26354 26379 +25 ========================================== Hits 10695 10695 - Misses 15659 15684 +25 ```

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