Godot 4.1.3, Dodge the Creeps 2D mobs stop moving

Question

Hey all, just built the DtC2D game. I was playing around with some parameters and decided to lower the mob velocity range:

`# Choose the velocity for the mob.
var velocity = Vector2(randf_range(50.0, 60.0), 0.0)
mob.linear_velocity = velocity.rotated(direction)`

(I believe tutorial had 150.0, 250.0 as the range). Anyway, slower mobs seem to spawn in an move as intended, but as they move across the screen, slow down gradually until become immobile...they are still animated, just not moving with any velocity. I'm not sure if mobs that are traveling faster are doing this too, but just happen to move through the screen and despawn before it becomes noticeable. Any ideas why this is happening?

Acriflavine

Answer 1

Seems to work fine for me from what I can tell. Can you show a video of what is happening or some other code that might be related?

Isodimorphism

Answer 2

but as they move across the screen, slow down gradually until become immobile...

Seems to work fine for me from what I can tell.

I checked. I confirm the problem. In G4.2, it's the same situation.

Iridis

Answer 3

Really? I did not notice but maybe it took too long to slow down.

Isodimorphism

Answer 4

Really?

Uh-huh. 😃 I've set the same parameters as TS.

Iridis

Answer 5

How long did it take for the effect to become noticeable?

Isodimorphism

Answer 6

Immediately. The very first mobs start slowing down.

Iridis

Answer 7

Ah I see. Because that wasn't happening for me at all.

Isodimorphism

Answer 8

I just tried making that change in a Godot 3 version of Dodge the Creeps. In that case, the creeps (RigidBody2D's) slow down because they start filling up the screen and colliding with each other.

I ran into a similar problem in a game I'm developing. To solve it, I placed a limit on the number of enemies that can exist at a time, and also apply random forces to keep them moving.

Verbose

Answer 9

In that case, the creeps (RigidBody2D's) slow down because they start filling up the screen and colliding with each other.

Well, are they supposed to affect each other? 😕

Iridis

Answer 10

They're RigidBody2D's. You can give them an initial velocity. After that, their behavior is controlled by physics.

Verbose

Answer 11

After that, their behavior is controlled by the physics engine.

They have disabled physical interaction with each other in the layers:

In addition, under the CollisionObject2D section just beneath the RigidBody2D section, expand the Collision group and uncheck the 1 inside the Mask property. This will ensure the mobs do not collide with each other.

What's slowing them down?

Iridis

Answer 12

I must have missed that instruction. If I uncheck the 1 inside the Mask property, then the creeps don't collide, but they do slow down.

So I can confirm the problem, and apparently it's not new to Godot 4.

Verbose

Answer 13

If I change the property RigidBody2D.linear_damp from -1 to 0, then the slowdown does not occur. That's in Godot 3.5.3.

Verbose

Answer 14

Thanks for the confirmation everyone.

If I change the property RigidBody2D.linear_damp from -1 to 0, then the slowdown does not occur. That's in Godot 3.5.3.

Interesting...but it looks like it was already set to 0 in the version of the tutorial I built from.

Acriflavine

Answer 15

Is linear_damp_mode also 0? If so, try changing it to 1.

Verbose

Answer 16

I played around with RigidBody2D.linear_damp. When I set it to -1, the speed gets "negatively damped" (the mobs noticably accelerate as they cross the screen). Setting it to roughly -0.1 seemed to counterbalance the deceleration that I was noticing from before, allowing the mobs to maintain approximately a constant speed before they exit and despawn.

So, that'll work around the issue temporarily, but I assume having any slowdown when linear damp is set to 0 wasn't the intended behavior.

Acriflavine

Answer 17

linear_damp_mode is also a factor.

Verbose

Answer 18

Is linear_damp_mode also 0? If so, try changing it to 1.

Thanks! damp_mode was set to 0 (combine)...setting it to 1 (replace) seemed to fix it. Mobs now seem to maintain their initial speed when damp is set to 0.

Huh, I wonder if there is a reason for the discrepancy in behavior between modes when damping is set to 0 anyway.

Acriflavine

Answer 19

damp_mode was set to 0 (combine)...setting it to 1 (replace) seemed to fix it.

It might be reasonable to add this to the documentation.

Iridis