How do I avoid a 1-frame delay between cursor and something moving with cursor? | Bevy | Page 1

sullen flint Oct 31, 2022, 6:28 PM

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When the player drags an item with the cursor, the item is one frame behind. I used to just kind of put up with this, but I am pretty sure on a recent build/launch, this didn't happen. So now that I am pretty sure it's possible for it to not happen, how do I make it consistently not happen?

cunning tapir Oct 31, 2022, 8:27 PM

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I think this should mostly be a matter of figuring out when input polling happens and queueing your movement system right after

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But you also need the constraint that this should still happen before rendering

sullen flint Oct 31, 2022, 8:44 PM

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I had assumed input polling would happen before the main stage

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or the update stage or whatever

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but maybe rendering happens in postupdate, I am moving my mesh there currently 🤔

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Maybe I should just make my own stage

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OK that changed nothing

cobalt gust Oct 31, 2022, 9:13 PM

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sullen flint or the update stage or whatever

Have you checked that it does? Not to sound pedantic but I recently found Rapier polls on the Update stage. Which was unexpected to say the least.

sullen flint Oct 31, 2022, 9:35 PM

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I don't know how I would check

cobalt gust Oct 31, 2022, 10:17 PM

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So if you're using the default plugins it's not that hard to track it down.
https://github.com/bevyengine/bevy/blob/main/crates/bevy_internal/src/default_plugins.rs#L37
https://github.com/bevyengine/bevy/blob/main/crates/bevy_input/src/lib.rs#L59

sullen flint Oct 31, 2022, 10:19 PM

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Think you meant this line https://github.com/bevyengine/bevy/blob/main/crates/bevy_input/src/lib.rs#L69

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hmm

cobalt gust Oct 31, 2022, 10:19 PM

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So it looks like all the input is handled in PreUpdate

sullen flint Oct 31, 2022, 10:19 PM

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Can you like... click through to things like in IDE

cobalt gust Oct 31, 2022, 10:19 PM

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Are you not using Rust Analyser?

sullen flint Oct 31, 2022, 10:20 PM

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I mean can you do that in github?

cobalt gust Oct 31, 2022, 10:20 PM

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Oh no... I just searched for it.

sullen flint Oct 31, 2022, 10:20 PM

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damn, would've been nice

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Trying to do the same with the render plug-in is maybe not as enlightening

cobalt gust Oct 31, 2022, 10:22 PM

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So how are you adding your movement code? Just adding a single system without specifying a stage?

sullen flint Oct 31, 2022, 10:22 PM

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Not specifying a stage explicitly means CoreStage::Update doesn't it?

cobalt gust Oct 31, 2022, 10:22 PM

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Yeah exactly.

sullen flint Oct 31, 2022, 10:23 PM

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Everything is in CoreStage::Update, except my mesh change, which is in CoreStage::PostUpdate

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but when I tried to add a stage in between the two, for the mesh change, it didn't change outcome noticeably

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I am not sure rendering happens in any particular core stage

cunning tapir Oct 31, 2022, 10:42 PM

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I forgot about this earlier, but rendering always runs essentially one frame later. see this section of the 0.6 release for more detail https://bevyengine.org/news/bevy-0-6/#pipelined-rendering-extract-prepare-queue-render

Bevy - Bevy 0.6

Bevy is a refreshingly simple data-driven game engine built in Rust. It is free and open-source forever!

sullen flint Oct 31, 2022, 10:44 PM

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Could've sworn it was smooth just once, I remember taking note of it

cunning tapir Oct 31, 2022, 10:45 PM

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In other words exactly one frame delay is inevitable, but if it's noticeable it probably means either low fps, something is wrong or you are unfortunately very sensitive to input delay

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You might want to give https://github.com/aevyrie/bevy_framepace a try

sullen flint Oct 31, 2022, 10:49 PM

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I remember being surprised

sullen flint Oct 31, 2022, 11:05 PM

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cunning tapir In other words exactly one frame delay is inevitable, but if it's noticeable it ...

Don't need to be very sensitive when using OS cursor to move in-game meshes

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I'm in the process of making a game cursor there

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which will hide the problem somewhat

cunning tapir Oct 31, 2022, 11:07 PM

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sullen flint Don't need to be very sensitive when using OS cursor to move in-game meshes

I just know I've heard people talk about noticeable input delays in things where I personally didn't notice anything. So it's always hard for me to have an opinion on this.

sullen flint Oct 31, 2022, 11:08 PM

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Same, supposedly Dota 2 did it worse than HoN

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but HoN is dead now, soo

cunning tapir Oct 31, 2022, 11:08 PM

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Damn, HoN, haven't seen that name in a long time lol

sullen flint Oct 31, 2022, 11:09 PM

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pub fn cursor_mesh() -> Mesh {
    let mut mesh = Mesh::new(PrimitiveTopology::TriangleList);
    mesh.insert_vertices([Vec3::ZERO, Vec3::NEG_Y, Vec3::X]);
    mesh.compute_flat_normals();
    mesh
}

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I was thinking how I would make a placeholder cursor mesh

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trying to like... reason out the triangles it would consist of

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then after one triangle I was like wait I can stop here

cunning tapir Oct 31, 2022, 11:12 PM

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I'd just use a quad with an image personally

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that way you can have fancy cursors without any unnecessary triangles

sullen flint Oct 31, 2022, 11:13 PM

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well it's just a placeholder, I am mostly trying to get the networking down

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You know, unrelatedly, I am getting really sick of that garish orange background

#How do I avoid a 1-frame delay between cursor and something moving with cursor?