Controls

Setting Up egui

We want to be able to control the playback of the point cloud data. By pausing or by manually selecting a frame to display.

We will use egui for this application as it has a rich widget library and is easy to use.

It has a plugin for Bevy, bevy_egui. We can add the EguiPlugin to our app.

As we have multiple cameras, we need to help egui know to which camera it should render to. We will need to set the auto_create_primary_context field to false on the EguiGlobalSettings resource, and add the PrimaryEguiContext component to the camera we choose.

Rendering the UI

bevy_egui is rendering in immediate mode. We will need a system in the EguiPrimaryContextPass schedule to draw the UI.

#![allow(unused)]
fn main() {
extern crate bevy;
extern crate bevy_ecs;
extern crate bevy_egui;
use bevy::{
    camera::{Viewport, visibility::RenderLayers},
    prelude::*,
    render::view::NoIndirectDrawing,
    window::WindowResized,
};
use bevy_egui::{
    EguiContexts, EguiGlobalSettings, EguiPlugin, EguiPrimaryContextPass, PrimaryEguiContext, egui,
};
#[derive(Resource)]
struct Play {
    current_frame: u32,
    frame_count: u32,
    playing: bool,
}

fn controls(
    mut contexts: EguiContexts,
    mut play: ResMut<Play>,
) -> Result {
    egui::TopBottomPanel::top("Controls").show(contexts.ctx_mut()?, |ui| {
        ui.horizontal(|ui| {
            let frame_count = play.frame_count;
            ui.add(egui::Slider::new(&mut play.current_frame, 0..=frame_count).text("Frame"));
            if ui
                .button(if play.playing { "Pause" } else { "Play" })
                .clicked()
            {
                play.playing = !play.playing;
            }
        });
    });
    Ok(())
}
}