comet/crates/comet_renderer/src/batch.rs

use comet_resources::Vertex;
use wgpu::util::DeviceExt;
use wgpu::{BufferUsages, Device};

pub struct Batch {
    label: String,
    vertex_data: Vec<Vertex>,
    index_data: Vec<u16>,
    vertex_buffer: wgpu::Buffer,
    index_buffer: wgpu::Buffer,
    num_indices: u32,
}

impl Batch {
    pub fn new(
        label: String,
        device: &Device,
        vertex_data: Vec<Vertex>,
        index_data: Vec<u16>,
    ) -> Self {
        let vertex_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some(format!("{} Vertex Buffer", &label).as_str()),
            contents: bytemuck::cast_slice(&vertex_data),
            usage: BufferUsages::VERTEX | BufferUsages::COPY_DST,
        });

        let num_indices = index_data.len() as u32;

        let index_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some(format!("{} Index Buffer", &label).as_str()),
            contents: bytemuck::cast_slice(&index_data),
            usage: BufferUsages::INDEX | BufferUsages::COPY_DST,
        });

        Self {
            label,
            vertex_data,
            index_data,
            vertex_buffer,
            index_buffer,
            num_indices,
        }
    }

    pub fn vertex_buffer(&self) -> &wgpu::Buffer {
        &self.vertex_buffer
    }

    pub fn vertex_data(&self) -> &Vec<Vertex> {
        &self.vertex_data
    }

    pub fn index_buffer(&self) -> &wgpu::Buffer {
        &self.index_buffer
    }

    pub fn index_data(&self) -> &Vec<u16> {
        &self.index_data
    }

    pub fn num_indices(&self) -> u32 {
        self.num_indices
    }

    pub fn update_vertex_buffer(
        &mut self,
        device: &Device,
        queue: &wgpu::Queue,
        vertex_data: Vec<Vertex>,
    ) {
        let new_vertex_size = vertex_data.len() as u64 * size_of::<Vertex>() as u64;
        match vertex_data == self.vertex_data {
            true => {}
            false => {
                match new_vertex_size > self.vertex_buffer.size() {
                    false => queue.write_buffer(
                        &self.vertex_buffer,
                        0,
                        bytemuck::cast_slice(&vertex_data),
                    ),
                    true => {
                        self.vertex_buffer =
                            device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
                                label: Some(format!("{} Vertex Buffer", self.label).as_str()),
                                contents: bytemuck::cast_slice(&vertex_data),
                                usage: BufferUsages::VERTEX | BufferUsages::COPY_DST,
                            });
                    }
                }
                self.vertex_data = vertex_data;
            }
        }
    }

    pub fn update_index_buffer(
        &mut self,
        device: &Device,
        queue: &wgpu::Queue,
        index_data: Vec<u16>,
    ) {
        let new_index_size = index_data.len() as u64 * size_of::<u16>() as u64;
        match index_data == self.index_data {
            true => {}
            false => {
                match new_index_size > self.index_buffer.size() {
                    false => {
                        queue.write_buffer(&self.index_buffer, 0, bytemuck::cast_slice(&index_data))
                    }
                    true => {
                        self.index_buffer =
                            device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
                                label: Some(format!("{} Index Buffer", self.label).as_str()),
                                contents: bytemuck::cast_slice(&index_data),
                                usage: BufferUsages::INDEX | BufferUsages::COPY_DST,
                            });
                    }
                }
                self.num_indices = index_data.len() as u32;
                self.index_data = index_data;
            }
        }
    }
}