Fix move_and_slide wall slide acceleration (3D)

[rburing]

When travel is high enough, keep the global position resulting from the move_and_collide call, and set the motion to the remainder from the move_and_collide call. This ensures travel is taken into account once, rather than twice.

This is also consistent with the other branch:

godot/scene/3d/physics/character_body_3d.cpp

Lines 241 to 242 in 2efbc6b

	// If the movement is not canceled we only keep the remaining.
	motion = result.remainder;

Thanks to @Calinou for extra testing.

• Fixes CharacterBody3D gains extra speed proportional to physics FPS when walking along walls with floor_block_on_wall = true #66249
• Fixes CharacterBody3D's real velocity is inaccurate when colliding #74553
• Fixes CharacterBody3D sliding along a wall with move_and_slide() has unexpected speed at certain angles #90410

[rburing]

For ease of reviewing: the travel is taken into account in the call

godot/scene/3d/physics/character_body_3d.cpp

Line 159 in 2efbc6b

bool collided = move_and_collide(parameters, result, false, !sliding_enabled);

which passes p_test_only = false into move_and_collide:

godot/scene/3d/physics/physics_body_3d.cpp

Lines 155 to 159 in 80c600d

	if (!p_test_only) {
	Transform3D gt = p_parameters.from;
	gt.origin += r_result.travel;
	set_global_transform(gt);
	}

[fabriceci]

Great job!

I had a bit of free time and I was looking to fix this problem, I found the PR while looking for the issues :)

To add a bit of context, this line belongs to a block of code that cancels a movement when you run against a surface considered to be a wall.

If the speed is too fast, the movement cannot be reversed as this would create a gap between the wall and the body.

(Prepare yourself for a very high quality graphic)

It was a case I hadn't anticipated!

I tested the reproduction project of the bug as well as the scenario I illustrated to see if it still works properly, and everything is perfect!

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 4.2.3.