wgpu-renderer/src/core/instance.rs

use super::model::Vertex;

pub struct Instance {
    pub position: cgmath::Vector3<f32>,
    pub rotation: cgmath::Quaternion<f32>,
}

#[repr(C)]
#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
pub struct InstanceRaw {
    pub model: [[f32; 4]; 4],
}

impl Instance {
    pub fn to_raw(&self) -> InstanceRaw {
        return InstanceRaw {
            model: (cgmath::Matrix4::from_translation(self.position)
                * cgmath::Matrix4::from(self.rotation))
            .into(),
        };
    }
}

impl Vertex for InstanceRaw {
    fn desc<'a>() -> wgpu::VertexBufferLayout<'a> {
        use std::mem;
        wgpu::VertexBufferLayout {
            array_stride: mem::size_of::<InstanceRaw>() as wgpu::BufferAddress,
            // We need to switch from using a step mode of Vertex to Instance
            // This means that our shaders will only change to use the next
            // instance when the shader starts processing a new instance
            step_mode: wgpu::VertexStepMode::Instance,
            attributes: &[
                wgpu::VertexAttribute {
                    offset: 0,
                    shader_location: 5,
                    format: wgpu::VertexFormat::Float32x4,
                },
                wgpu::VertexAttribute {
                    offset: mem::size_of::<[f32; 4]>() as wgpu::BufferAddress,
                    shader_location: 6,
                    format: wgpu::VertexFormat::Float32x4,
                },
                wgpu::VertexAttribute {
                    offset: mem::size_of::<[f32; 8]>() as wgpu::BufferAddress,
                    shader_location: 7,
                    format: wgpu::VertexFormat::Float32x4,
                },
                wgpu::VertexAttribute {
                    offset: mem::size_of::<[f32; 12]>() as wgpu::BufferAddress,
                    shader_location: 8,
                    format: wgpu::VertexFormat::Float32x4,
                },
            ],
        }
    }
}