cvkg_render_gpu/

lib.rs

//! # CVKG Agentic Development Guidelines (v1.2)
//!
//! All AI agents contributing to this crate MUST follow ALL seven rules:
//!
//! ── Karpathy Guidelines (1–4) ────────────────────────────────────────────
//! 1. THINK FIRST     — State assumptions. Surface ambiguity. Push back on complexity.
//! 2. STAY SIMPLE     — Minimum code. No speculative features. No unasked-for abstractions.
//! 3. BE SURGICAL     — Touch only what's required. Own your orphans. Don't improve neighbors.
//! 4. VERIFY GOALS    — Turn tasks into checkable criteria. Loop until they pass. Never commit broken.
//!
//! ── CVKG Extended Protocols (5–7) ────────────────────────────────────────
//! 5. TRIPLE-PASS     — Read the target, its surrounding context, and its full call graph
//!                      at least THREE TIMES before making any edit or revision.
//! 6. COMMENT ALL     — Every major pub fn, unsafe block, and non-trivial algorithm in
//!                      every .rs/.ts/.h/.wgsl file MUST have a descriptive doc comment.
//!                      Comments describe WHY and WHAT CONTRACT, not HOW mechanically.
//! 7. MONITOR LOOPS   — Check every tool call / command for progress every 30 seconds.
//!                      After 3 consecutive identical failures, stop, write BLOCKED.md,
//!                      and move to unblocked work. Never silently accept a broken state.
//!
//! Sources:
//!   Karpathy: https://github.com/multica-ai/andrej-karpathy-skills
//!   CVKG Extended: Section 2 of the CVKG Design Specification

//! # Surtr Render Pipeline
//!
//! The "Fiery Giant" of the CVKG architecture. This is the authoritative GPU renderer
//! powered by `wgpu`. It manages the heat of the GPU to forge high-fidelity 
//! "Berserker" aesthetics.
//!
//! - **The Flaming Sword**: Command submission and synchronization.
//! - **Muspelheim Passes**: Multi-pass Gaussian blur and bloom for Bifrost/Gungnir.

use cvkg_core::Rect;
use std::sync::Arc;

// ShieldWall — re-export AccessKit types so callers can build tree updates
// without depending on accesskit directly.
pub use accesskit::{
    ActionHandler, ActionRequest, ActivationHandler, DeactivationHandler,
    Node, NodeId, Role, Tree, TreeId, TreeUpdate,
};
pub use accesskit_winit::Adapter as ShieldWallAdapter;


#[repr(C)]
#[derive(Copy, Clone, Debug, bytemuck::Pod, bytemuck::Zeroable)]
pub struct Vertex {
    pub position: [f32; 2],
    pub uv: [f32; 2],
    pub color: [f32; 4],
    pub mode: u32,
}

impl Vertex {
    const ATTRIBUTES: [wgpu::VertexAttribute; 4] = wgpu::vertex_attr_array![
        0 => Float32x2,
        1 => Float32x2,
        2 => Float32x4,
        3 => Uint32
    ];

    fn desc() -> wgpu::VertexBufferLayout<'static> {
        wgpu::VertexBufferLayout {
            array_stride: std::mem::size_of::<Vertex>() as wgpu::BufferAddress,
            step_mode: wgpu::VertexStepMode::Vertex,
            attributes: &Self::ATTRIBUTES,
        }
    }
}

/// SurtrRenderer implements the high-performance GPU backend.
pub struct SurtrRenderer {
    device: Arc<wgpu::Device>,
    queue: Arc<wgpu::Queue>,
    surface: wgpu::Surface<'static>,
    config: wgpu::SurfaceConfiguration,
    pipeline: wgpu::RenderPipeline,
    
    // Muspelheim Pass Resources
    bloom_extract_pipeline: wgpu::RenderPipeline,
    blur_h_pipeline: wgpu::RenderPipeline,
    blur_v_pipeline: wgpu::RenderPipeline,
    composite_pipeline: wgpu::RenderPipeline,
    blur_texture_a: wgpu::TextureView,
    blur_texture_b: wgpu::TextureView,
    blur_bind_group_a: wgpu::BindGroup,
    blur_bind_group_b: wgpu::BindGroup,
    
    // Text Forge
    font_system: cosmic_text::FontSystem,
    swash_cache: cosmic_text::SwashCache,

    // Niflheim Resources
    dummy_bind_group: wgpu::BindGroup,

    // The Forge's Anvil (GPU Buffers)
    vertex_buffer: wgpu::Buffer,
    index_buffer: wgpu::Buffer,
    vertices: Vec<Vertex>,
    indices: Vec<u16>,
}

const MAX_VERTICES: usize = 10000;
const MAX_INDICES: usize = 15000;

impl SurtrRenderer {
    /// Forge a new SurtrRenderer from a winit window.
    pub async fn forge(window: Arc<winit::window::Window>) -> Self {
        let instance = wgpu::Instance::default();
        let surface = instance.create_surface(window.clone()).unwrap();
        let adapter = instance.request_adapter(&wgpu::RequestAdapterOptions {
            power_preference: wgpu::PowerPreference::HighPerformance,
            compatible_surface: Some(&surface),
            force_fallback_adapter: false,
        }).await.expect("Failed to find a suitable GPU for Surtr");

        let (device, queue) = adapter.request_device(
            &wgpu::DeviceDescriptor {
                label: Some("Surtr Forge"),
                required_features: wgpu::Features::empty(),
                required_limits: wgpu::Limits::default(),
            },
            None,
        ).await.expect("Failed to create Surtr device");

        let device = Arc::new(device);
        let queue = Arc::new(queue);
        
        let size = window.inner_size();
        let config = surface.get_default_config(&adapter, size.width, size.height).unwrap();
        surface.configure(&device, &config);

        // Load the Muspelheim Shaders
        let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
            label: Some("Muspelheim Main Shader"),
            source: wgpu::ShaderSource::Wgsl(include_str!("shaders.wgsl").into()),
        });

        // Niflheim Bind Group Layout (for textures/samplers)
        let texture_bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
            entries: &[
                wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Texture {
                        multisampled: false,
                        view_dimension: wgpu::TextureViewDimension::D2,
                        sample_type: wgpu::TextureSampleType::Float { filterable: true },
                    },
                    count: None,
                },
                wgpu::BindGroupLayoutEntry {
                    binding: 1,
                    visibility: wgpu::ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
                    count: None,
                },
            ],
            label: Some("Niflheim Texture Bind Group Layout"),
        });

        // Pipeline setup
        let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
            label: Some("Surtr Pipeline Layout"),
            bind_group_layouts: &[&texture_bind_group_layout],
            push_constant_ranges: &[],
        });

        let pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("Surtr Main Pipeline"),
            layout: Some(&pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: "vs_main",
                buffers: &[Vertex::desc()],
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "fs_main",
                targets: &[Some(wgpu::ColorTargetState {
                    format: config.format,
                    blend: Some(wgpu::BlendState::ALPHA_BLENDING),
                    write_mask: wgpu::ColorWrites::ALL,
                })],
            }),
            primitive: wgpu::PrimitiveState::default(),
            depth_stencil: None,
            multisample: wgpu::MultisampleState::default(),
            multiview: None,
        });

        // Muspelheim Bloom Extract Pipeline
        let bloom_extract_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("Muspelheim Bloom Extract"),
            layout: Some(&pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: "vs_fullscreen",
                buffers: &[],
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "fs_bloom_extract",
                targets: &[Some(wgpu::ColorTargetState {
                    format: config.format,
                    blend: None,
                    write_mask: wgpu::ColorWrites::ALL,
                })],
            }),
            primitive: wgpu::PrimitiveState::default(),
            depth_stencil: None,
            multisample: wgpu::MultisampleState::default(),
            multiview: None,
        });

        // Muspelheim Blur Pipelines (H and V)
        let blur_h_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("Muspelheim Horizontal Blur"),
            layout: Some(&pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: "vs_fullscreen",
                buffers: &[],
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "fs_blur_h",
                targets: &[Some(wgpu::ColorTargetState {
                    format: config.format,
                    blend: Some(wgpu::BlendState::ALPHA_BLENDING),
                    write_mask: wgpu::ColorWrites::ALL,
                })],
            }),
            primitive: wgpu::PrimitiveState::default(),
            depth_stencil: None,
            multisample: wgpu::MultisampleState::default(),
            multiview: None,
        });

        let blur_v_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("Muspelheim Vertical Blur"),
            layout: Some(&pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: "vs_fullscreen",
                buffers: &[],
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "fs_blur_v",
                targets: &[Some(wgpu::ColorTargetState {
                    format: config.format,
                    blend: Some(wgpu::BlendState::ALPHA_BLENDING),
                    write_mask: wgpu::ColorWrites::ALL,
                })],
            }),
            primitive: wgpu::PrimitiveState::default(),
            depth_stencil: None,
            multisample: wgpu::MultisampleState::default(),
            multiview: None,
        });

        // Muspelheim Composite Pipeline (additive blend onto screen)
        let composite_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("Muspelheim Composite"),
            layout: Some(&pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: "vs_fullscreen",
                buffers: &[],
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "fs_composite",
                targets: &[Some(wgpu::ColorTargetState {
                    format: config.format,
                    // Additive blend: src + dst — glow lights up the scene
                    blend: Some(wgpu::BlendState {
                        color: wgpu::BlendComponent {
                            src_factor: wgpu::BlendFactor::One,
                            dst_factor: wgpu::BlendFactor::One,
                            operation: wgpu::BlendOperation::Add,
                        },
                        alpha: wgpu::BlendComponent {
                            src_factor: wgpu::BlendFactor::One,
                            dst_factor: wgpu::BlendFactor::One,
                            operation: wgpu::BlendOperation::Add,
                        },
                    }),
                    write_mask: wgpu::ColorWrites::ALL,
                })],
            }),
            primitive: wgpu::PrimitiveState::default(),
            depth_stencil: None,
            multisample: wgpu::MultisampleState::default(),
            multiview: None,
        });

        // Muspelheim Intermediate Textures
        let blur_tex_desc = wgpu::TextureDescriptor {
            label: Some("Muspelheim Intermediate"),
            size: wgpu::Extent3d {
                width: config.width,
                height: config.height,
                depth_or_array_layers: 1,
            },
            mip_level_count: 1,
            sample_count: 1,
            dimension: wgpu::TextureDimension::D2,
            format: config.format,
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT | wgpu::TextureUsages::TEXTURE_BINDING,
            view_formats: &[],
        };
        let blur_texture_a_obj = device.create_texture(&blur_tex_desc);
        let blur_texture_b_obj = device.create_texture(&blur_tex_desc);
        let blur_texture_a = blur_texture_a_obj.create_view(&wgpu::TextureViewDescriptor::default());
        let blur_texture_b = blur_texture_b_obj.create_view(&wgpu::TextureViewDescriptor::default());

        let sampler = device.create_sampler(&wgpu::SamplerDescriptor {
            address_mode_u: wgpu::AddressMode::ClampToEdge,
            address_mode_v: wgpu::AddressMode::ClampToEdge,
            mag_filter: wgpu::FilterMode::Linear,
            ..Default::default()
        });

        let blur_bind_group_a = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &texture_bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry { binding: 0, resource: wgpu::BindingResource::TextureView(&blur_texture_a) },
                wgpu::BindGroupEntry { binding: 1, resource: wgpu::BindingResource::Sampler(&sampler) },
            ],
            label: Some("Blur Bind Group A"),
        });

        let blur_bind_group_b = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &texture_bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry { binding: 0, resource: wgpu::BindingResource::TextureView(&blur_texture_b) },
                wgpu::BindGroupEntry { binding: 1, resource: wgpu::BindingResource::Sampler(&sampler) },
            ],
            label: Some("Blur Bind Group B"),
        });

        // Forge the Niflheim Dummy Texture (1x1 White)
        let dummy_size = wgpu::Extent3d {
            width: 1,
            height: 1,
            depth_or_array_layers: 1,
        };
        let dummy_texture = device.create_texture(&wgpu::TextureDescriptor {
            label: Some("Niflheim Dummy Texture"),
            size: dummy_size,
            mip_level_count: 1,
            sample_count: 1,
            dimension: wgpu::TextureDimension::D2,
            format: wgpu::TextureFormat::Rgba8UnormSrgb,
            usage: wgpu::TextureUsages::TEXTURE_BINDING | wgpu::TextureUsages::COPY_DST,
            view_formats: &[],
        });
        queue.write_texture(
            wgpu::ImageCopyTexture {
                texture: &dummy_texture,
                mip_level: 0,
                origin: wgpu::Origin3d::ZERO,
                aspect: wgpu::TextureAspect::All,
            },
            &[255, 255, 255, 255],
            wgpu::ImageDataLayout {
                offset: 0,
                bytes_per_row: Some(4),
                rows_per_image: Some(1),
            },
            dummy_size,
        );

        let dummy_view = dummy_texture.create_view(&wgpu::TextureViewDescriptor::default());
        let dummy_sampler = device.create_sampler(&wgpu::SamplerDescriptor {
            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: wgpu::FilterMode::Nearest,
            mipmap_filter: wgpu::FilterMode::Nearest,
            ..Default::default()
        });

        let dummy_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &texture_bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry {
                    binding: 0,
                    resource: wgpu::BindingResource::TextureView(&dummy_view),
                },
                wgpu::BindGroupEntry {
                    binding: 1,
                    resource: wgpu::BindingResource::Sampler(&dummy_sampler),
                },
            ],
            label: Some("Niflheim Dummy Bind Group"),
        });

        // Forge the Anvil (Buffers)
        let vertex_buffer = device.create_buffer(&wgpu::BufferDescriptor {
            label: Some("Surtr Vertex Anvil"),
            size: (MAX_VERTICES * std::mem::size_of::<Vertex>()) as u64,
            usage: wgpu::BufferUsages::VERTEX | wgpu::BufferUsages::COPY_DST,
            mapped_at_creation: false,
        });

        let index_buffer = device.create_buffer(&wgpu::BufferDescriptor {
            label: Some("Surtr Index Anvil"),
            size: (MAX_INDICES * std::mem::size_of::<u16>()) as u64,
            usage: wgpu::BufferUsages::INDEX | wgpu::BufferUsages::COPY_DST,
            mapped_at_creation: false,
        });


        Self {
            device,
            queue,
            surface,
            config,
            pipeline,
            bloom_extract_pipeline,
            blur_h_pipeline,
            blur_v_pipeline,
            composite_pipeline,
            blur_texture_a,
            blur_texture_b,
            blur_bind_group_a,
            blur_bind_group_b,
            font_system: cosmic_text::FontSystem::new(),
            swash_cache: cosmic_text::SwashCache::new(),
            dummy_bind_group,
            vertex_buffer,
            index_buffer,
            vertices: Vec::with_capacity(MAX_VERTICES),
            indices: Vec::with_capacity(MAX_INDICES),
        }
    }

    /// Strike the flaming sword (begin frame).
    pub fn begin_frame(&mut self) -> wgpu::CommandEncoder {
        self.vertices.clear();
        self.indices.clear();
        self.device.create_command_encoder(&wgpu::CommandEncoderDescriptor {
            label: Some("Surtr's Flaming Sword"),
        })
    }

    /// Quench the blade — submits the full Muspelheim multi-pass effect:
    ///   Pass 1  — Base geometry → screen (clear + all solid/glow rects)
    ///   Pass 2  — Bloom extract from screen → tex_a (threshold bright pixels)
    ///   Pass 3–6 — Ping-pong blur (H→B, V→A, H→B, V→A) — 4 iters
    ///   Pass 7  — Additive composite  tex_a → screen  (glow on top)
    pub fn end_frame(&mut self, mut encoder: wgpu::CommandEncoder) {
        self.queue.write_buffer(&self.vertex_buffer, 0, bytemuck::cast_slice(&self.vertices));
        self.queue.write_buffer(&self.index_buffer, 0, bytemuck::cast_slice(&self.indices));

        let frame = self.surface.get_current_texture()
            .expect("Surtr: failed to acquire surface texture");
        let screen = frame.texture.create_view(&wgpu::TextureViewDescriptor::default());

        // ── Pass 1: Base scene → screen ─────────────────────────────────────
        {
            let mut p = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                label: Some("Surtr P1 Base"),
                color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                    view: &screen,
                    resolve_target: None,
                    ops: wgpu::Operations {
                        load: wgpu::LoadOp::Clear(wgpu::Color { r: 0.0, g: 0.0, b: 0.0, a: 1.0 }), // Ginnungagap
                        store: wgpu::StoreOp::Store,
                    },
                })],
                depth_stencil_attachment: None,
                occlusion_query_set: None,
                timestamp_writes: None,
            });
            if !self.indices.is_empty() {
                p.set_pipeline(&self.pipeline);
                p.set_bind_group(0, &self.dummy_bind_group, &[]);
                p.set_vertex_buffer(0, self.vertex_buffer.slice(..));
                p.set_index_buffer(self.index_buffer.slice(..), wgpu::IndexFormat::Uint16);
                p.draw_indexed(0..self.indices.len() as u32, 0, 0..1);
            }
        }

        // ── Pass 2: Bloom extract  screen → tex_a ────────────────────────────
        // Re-render geometry into tex_a at amplified brightness so the blur
        // has a source to operate on. fs_bloom_extract thresholds bright pixels.
        {
            let mut p = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                label: Some("Surtr P2 Bloom Src"),
                color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                    view: &self.blur_texture_a,
                    resolve_target: None,
                    ops: wgpu::Operations {
                        load: wgpu::LoadOp::Clear(wgpu::Color::TRANSPARENT),
                        store: wgpu::StoreOp::Store,
                    },
                })],
                depth_stencil_attachment: None,
                occlusion_query_set: None,
                timestamp_writes: None,
            });
            if !self.indices.is_empty() {
                p.set_pipeline(&self.pipeline);
                p.set_bind_group(0, &self.dummy_bind_group, &[]);
                p.set_vertex_buffer(0, self.vertex_buffer.slice(..));
                p.set_index_buffer(self.index_buffer.slice(..), wgpu::IndexFormat::Uint16);
                p.draw_indexed(0..self.indices.len() as u32, 0, 0..1);
            }
        }

        // ── Passes 3–6+: Ping-pong Gaussian blur (6 iterations) ──────────
        // 6 H+V pairs with a 5-tap kernel gives ~30px soft glow halo.
        let blur_iters: u32 = 6;
        for i in 0..blur_iters {
            // H pass: tex_a → tex_b
            {
                let label = format!("Surtr Blur H iter {}", i);
                let mut p = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                    label: Some(&label),
                    color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                        view: &self.blur_texture_b,
                        resolve_target: None,
                        ops: wgpu::Operations {
                            load: wgpu::LoadOp::Clear(wgpu::Color::TRANSPARENT),
                            store: wgpu::StoreOp::Store,
                        },
                    })],
                    depth_stencil_attachment: None,
                    occlusion_query_set: None,
                    timestamp_writes: None,
                });
                p.set_pipeline(&self.blur_h_pipeline);
                p.set_bind_group(0, &self.blur_bind_group_a, &[]);
                p.draw(0..3, 0..1);
            }
            // V pass: tex_b → tex_a
            {
                let label = format!("Surtr Blur V iter {}", i);
                let mut p = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                    label: Some(&label),
                    color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                        view: &self.blur_texture_a,
                        resolve_target: None,
                        ops: wgpu::Operations {
                            load: wgpu::LoadOp::Clear(wgpu::Color::TRANSPARENT),
                            store: wgpu::StoreOp::Store,
                        },
                    })],
                    depth_stencil_attachment: None,
                    occlusion_query_set: None,
                    timestamp_writes: None,
                });
                p.set_pipeline(&self.blur_v_pipeline);
                p.set_bind_group(0, &self.blur_bind_group_b, &[]);
                p.draw(0..3, 0..1);
            }
        }

        // ── Pass 7: Additive composite  tex_a → screen ──────────────────────
        // LoadOp::Load keeps the intact base scene; additive blend adds glow.
        {
            let mut p = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                label: Some("Surtr P7 Composite"),
                color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                    view: &screen,
                    resolve_target: None,
                    ops: wgpu::Operations {
                        load: wgpu::LoadOp::Load,
                        store: wgpu::StoreOp::Store,
                    },
                })],
                depth_stencil_attachment: None,
                occlusion_query_set: None,
                timestamp_writes: None,
            });
            p.set_pipeline(&self.composite_pipeline);
            p.set_bind_group(0, &self.blur_bind_group_a, &[]);
            p.draw(0..3, 0..1);
        }

        self.queue.submit(Some(encoder.finish()));
        frame.present();
    }

    /// Forge a rectangle into vertices
    pub fn fill_rect(&mut self, rect: Rect, color: [f32; 4], mode: u32) {
        let base_idx = self.vertices.len() as u16;
        
        // Normalize coordinates to NDC [-1, 1] (Assuming 800x600 for now, should use config)
        let x1 = (rect.x / 400.0) - 1.0;
        let y1 = 1.0 - (rect.y / 300.0);
        let x2 = ((rect.x + rect.width) / 400.0) - 1.0;
        let y2 = 1.0 - ((rect.y + rect.height) / 300.0);

        self.vertices.push(Vertex { position: [x1, y1], uv: [0.0, 0.0], color, mode });
        self.vertices.push(Vertex { position: [x2, y1], uv: [1.0, 0.0], color, mode });
        self.vertices.push(Vertex { position: [x2, y2], uv: [1.0, 1.0], color, mode });
        self.vertices.push(Vertex { position: [x1, y2], uv: [0.0, 1.0], color, mode });

        self.indices.extend_from_slice(&[
            base_idx, base_idx + 1, base_idx + 2,
            base_idx, base_idx + 2, base_idx + 3,
        ]);
    }
}