forte_engine 0.2.3

A core for a basic render/game engine designed to have little overhead.
Documentation 
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use wgpu::util::DeviceExt;

use crate::primitives::vertices::Vertex;

/// A simple struct that contains the information of mesh in a way that can be used by WGPU.
#[derive(Debug)]
pub struct Mesh {
    pub(crate) vertex_buf: wgpu::Buffer,
    pub(crate) index_buf: wgpu::Buffer,
    pub(crate) num_indices: u32,
    pub(crate) num_vertices: u32
}

impl Mesh {
    /// Create a new mesh from a WGPU device with vertices and indices arrays.
    /// 
    /// Arguments:
    /// * device: &wgpu::Device - The WGPU device to be used to create the buffers for this mesh.
    /// * vertices: &[Vertex] - The array of vertices for this mesh.
    /// * indices: &[u16] - The indices of this mesh.
    pub fn from_raw(device: &wgpu::Device, vertices: &[Vertex], indices: &[u16]) -> Self {
        Self {
            vertex_buf: device.create_buffer_init(
                &wgpu::util::BufferInitDescriptor {
                    label: Some("Vertex Buffer"),
                    contents: bytemuck::cast_slice(vertices),
                    usage: wgpu::BufferUsages::VERTEX
                }
            ),
            index_buf: device.create_buffer_init(
                &wgpu::util::BufferInitDescriptor {
                    label: Some("Index Buffer"),
                    contents: bytemuck::cast_slice(indices),
                    usage: wgpu::BufferUsages::INDEX
                }
            ),
            num_indices: indices.len() as u32,
            num_vertices: vertices.len() as u32
        }
    }

    /// Draws a mesh to this render pass.
    /// 
    /// Arguments:
    /// * self: &self - The mesh to be rendered
    /// * pass: &mut wgpu::RenderPass - The render pass to render too.
    /// * instance_buf: &wgpu::Buffer - The instances buffer to draw the mesh with.
    /// * instance_count: u32 - The number of instances in the above buffer.
    pub fn draw<'rpass>(
        &'rpass self,
        pass: &mut wgpu::RenderPass<'rpass>,
        instance_buffer: &'rpass wgpu::Buffer,
        instance_count: u32
    ) {
        pass.set_vertex_buffer(0, self.vertex_buf.slice(..));
        pass.set_vertex_buffer(1, instance_buffer.slice(..));
        pass.set_index_buffer(self.index_buf.slice(..), wgpu::IndexFormat::Uint16);
        pass.draw_indexed(0..self.num_indices, 0, 0..instance_count);
    }

    /// Draws a mesh to this render pass only using its vertices buffer.
    /// 
    /// Arguments:
    /// * self: &self - The mesh to be rendered
    /// * pass: &mut wgpu::RenderPass - The render pass to render too.
    /// * instance_buf: &wgpu::Buffer - The instances buffer to draw the mesh with.
    /// * instance_count: u32 - The number of instances in the above buffer.
    pub fn draw_list<'rpass>(
        &'rpass self,
        pass: &mut wgpu::RenderPass<'rpass>,
        instance_buffer: &'rpass wgpu::Buffer,
        instance_count: u32
    ) {
        pass.set_vertex_buffer(0, self.vertex_buf.slice(..));
        pass.set_vertex_buffer(1, instance_buffer.slice(..));
        pass.set_index_buffer(self.index_buf.slice(..), wgpu::IndexFormat::Uint16);
        pass.draw(0 .. self.num_vertices, 0..instance_count);
    }
}