ambient_gpu 0.2.1

Ambient GPU functionality. Host-only.
Documentation 
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use std::sync::Arc;

use ambient_std::asset_cache::{AssetCache, SyncAssetKey, SyncAssetKeyExt};
use wgpu::{BindGroupLayoutDescriptor, BindGroupLayoutEntry, FilterMode, PipelineLayoutDescriptor, ShaderStages, TextureSampleType};

use crate::shader_module::{Shader, ShaderIdent, ShaderModule};

use super::gpu::{Gpu, GpuKey};

#[derive(Debug, Clone)]
pub struct BlitterKey {
    pub format: wgpu::ColorTargetState,
    pub min_filter: FilterMode,
    pub gamma_correction: Option<f32>,
}

impl SyncAssetKey<Arc<Blitter>> for BlitterKey {
    fn load(&self, assets: AssetCache) -> Arc<Blitter> {
        Arc::new(Blitter::new(&assets, self))
    }
}

pub struct Blitter {
    pipeline: wgpu::RenderPipeline,
    sampler: wgpu::Sampler,
    gpu: Arc<Gpu>,
}
impl Blitter {
    pub fn new(assets: &AssetCache, conf: &BlitterKey) -> Self {
        let gpu = GpuKey.get(assets);

        log::debug!("Creating blitter: {conf:#?}");
        let colorspace = if let Some(gamma) = conf.gamma_correction {
            let inv_gamma = 1.0 / gamma;
            format!("vec4<f32>(pow(color.xyz, vec3<f32>({inv_gamma})), color.w)")
        } else {
            "color".to_string()
        };

        let shader = Shader::new(
            assets,
            "blitter",
            &[],
            &ShaderModule::new("blitter", include_str!("blit.wgsl")).with_ident(ShaderIdent::raw("COLORSPACE_EXPR", colorspace)),
        )
        .unwrap();

        let bind_group_layout = gpu.device.create_bind_group_layout(&BindGroupLayoutDescriptor {
            label: Some("blitter.bind_group_layout"),
            entries: &[
                BindGroupLayoutEntry {
                    binding: 0,
                    visibility: ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Texture {
                        sample_type: TextureSampleType::Float { filterable: true },
                        view_dimension: wgpu::TextureViewDimension::D2,
                        multisampled: false,
                    },
                    count: None,
                },
                BindGroupLayoutEntry {
                    binding: 1,
                    visibility: ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
                    count: None,
                },
            ],
        });

        let layout = gpu.device.create_pipeline_layout(&PipelineLayoutDescriptor {
            label: Some("blitter.layout"),
            bind_group_layouts: &[&bind_group_layout],
            push_constant_ranges: &[],
        });

        log::debug!("Setting up blitter");
        let pipeline = gpu.device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("Blitter.pipeline"),
            layout: Some(&layout),
            vertex: wgpu::VertexState { module: &shader, entry_point: "vs_main", buffers: &[] },
            fragment: Some(wgpu::FragmentState { module: &shader, entry_point: "fs_main", targets: &[Some(conf.format.clone())] }),
            primitive: wgpu::PrimitiveState { topology: wgpu::PrimitiveTopology::TriangleStrip, ..Default::default() },
            depth_stencil: None,
            multisample: wgpu::MultisampleState::default(),
            multiview: None,
        });

        let sampler = gpu.device.create_sampler(&wgpu::SamplerDescriptor {
            label: Some("Blitter.sampler"),
            address_mode_u: wgpu::AddressMode::ClampToEdge,
            address_mode_v: wgpu::AddressMode::ClampToEdge,
            address_mode_w: wgpu::AddressMode::ClampToEdge,
            mag_filter: wgpu::FilterMode::Linear,
            min_filter: conf.min_filter,
            mipmap_filter: wgpu::FilterMode::Nearest,
            ..Default::default()
        });

        Self { pipeline, sampler, gpu }
    }

    pub fn run(&self, encoder: &mut wgpu::CommandEncoder, source: &wgpu::TextureView, target: &wgpu::TextureView) {
        let bind_group_layout = self.pipeline.get_bind_group_layout(0);

        let bind_group = self.gpu.device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry { binding: 0, resource: wgpu::BindingResource::TextureView(source) },
                wgpu::BindGroupEntry { binding: 1, resource: wgpu::BindingResource::Sampler(&self.sampler) },
            ],
            label: None,
        });

        let mut rpass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
            label: None,
            color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                view: target,
                resolve_target: None,
                ops: wgpu::Operations { load: wgpu::LoadOp::Clear(wgpu::Color::WHITE), store: true },
            })],
            depth_stencil_attachment: None,
        });

        rpass.set_pipeline(&self.pipeline);
        rpass.set_bind_group(0, &bind_group, &[]);
        rpass.draw(0..4, 0..1);
    }
}