Collision model

[Try]

Gothic 2 collision are pretty tricky - need to investigate.

Proposed model

Collision shape of Npc:

• core - symmetrical "popsicle"
  • Y-aligned (symmetrical around character rotation axi) cylinder
  • Responsible, for conservative collision part and makes sure, that player wont go thru wall
  • Ray from center of cylinder to ground
  • Sample ground to estimate slide/fall
  • Object oriented bonding shape(probably ellipsoid)
  • Should not be violated (unless npc is spawned inside wall)
• extend - asymmetrical ellipse
  • might be slightly violated by rotation
  • relaxed collision check: report collision is collision depth increases

Special cases to test:

• Bloodfly (fly over water)
• Golem (can walk under water)
• Lurker (semi-broken animation)
• Sheep (can't enter water - no animations)
• Sheep (drown, if forced into water)
• Dragon (no water animation, takes a while to drown)
• Khorinis shipyard (too high)
• Khorinis shipyard (combat ai)
• Jarkentar underwater cave (no water plane in middle part)
• Scaled models (shrink monster; Mdl_SetModelScale)
• Transform spells
• Interaction with "movable-immovables": fake-walls or even doors
• Jump into water (npc should switch state to diving)
• Elevators (!)

Collision npc(human) vs landscape

1. Frontal
   
2. Side
   
3. Rotate after side collision
   

Collision npc(snapper) vs landscape

1. Frontal
   
2. Side
   

[Try]

From #575:

Game had some issues with npc-origin point and it interaction with collision. Probably it's time to get rid of translateY and related hacks and make OpenGothic more like vanilla on this aspect.

[Try]

Some testing of collisions:

Running asymmetrical npc, wolf in that case, into a wall resulting at one type of collision.
Side-walk and then rotation - allows to dip into a wall.

After dip into a wall: no way to move forward, but side-move will push npc back from the wall.
Makes me think, that this can be not a 'real' collider proxy, but just a set of six rays to estimate distances.