Medusa Slockbower
ff27caab4f
- Added boost-atomic and boost-thread as dependencies for concurrency support
219 lines
7.9 KiB
Markdown
219 lines
7.9 KiB
Markdown
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# 3D Graphics (`gfx3d`)
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## Table of Contents
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<!-- TOC -->
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* [Home](./CONTENTS.md#planning-documentation-for-fennec)
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* [3D Graphics (`gfx3d`)](#3d-graphics-gfx3d)
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* [Table of Contents](#table-of-contents)
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* [Introduction](#introduction)
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* [Structures](#structures)
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* [Stages](#stages)
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<!-- TOC -->
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## Introduction
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  This system handles the rendering of 3D meshes, materials, lights, and post-processing
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effects.
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**DirectX will never have official support.**
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If you would like to make a fork, have at it, but know that I will hold a deep disdain for you.
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The graphics pipeline will have a buffer with a list of objects and their rendering data.
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This will be referred to as the Object Buffer. There will be two, for both the Deferred and Forward Passes.
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The buffers will be optimized by scene prediction.
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This involves tracking the meshes and textures directly and indirectly used by a scene.
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A callback function in the graphics system for scene loading can do this.
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Materials and Lighting models will be run via a shader metaprogram to make the pipeline independent of this aspect.
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This allows the GPU to draw every single deferred rendered mesh in a single draw call for each stage of the renderer.
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Specifications for debugging views via early breaks are included in the stages.
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Links:
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- https://en.wikipedia.org/wiki/Octree
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- https://www.adriancourreges.com/blog/2015/11/02/gta-v-graphics-study/
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- https://learnopengl.com/PBR/Lighting
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- https://learnopengl.com/PBR/IBL/Diffuse-irradiance
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- https://en.wikipedia.org/wiki/Schlick%27s_approximation
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- https://pixelandpoly.com/ior.html
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- https://developer.download.nvidia.com/SDK/10/opengl/screenshots/samples/dual_depth_peeling.html
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## Structures
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Object Structure. The mesh is implicit data.
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```c++
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struct Object
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{
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vec3 location, scale; // A matrix would be 64 bytes, this is instead 28 bytes
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quat rotation;
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uint32 material, lighting;
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}
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```
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Objects are identified with a manually provided type and ID. Object types include:
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- Static (transform does not change after creation)
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- Dynamic (transform changes after creation)
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- Forward Static (object is forward rendered and its transform does not change after creation)
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A user should never have to specify these and should be automatically generated by the respective components.
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Textures for 3D rendering are stored in various buffers with sizes of powers of 2. Ratios of `1:1`
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and `2:1` are allowed. The `2:1` ratio is specifically for spherical and cylindrical projection. UVs
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may be transformed to use a `2:1` as if it were `1:2`.
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Cubemaps and 3D textures may only be `1:1`.
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- 8-Bit R Texture `4096, 2048, 1024, 512` (8)
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- 8-Bit RG Texture `4096, 2048, 1024, 512` (8)
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- 8-Bit RGB Texture `4096, 2048, 1024, 512` (8)
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- 8-Bit RGBA Texture `4096, 2048, 1024, 512` (8)
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- 8-Bit R Cubemap `1024, 512, 256, 128` (4)
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- 8-Bit RGB Cubemap `1024, 512, 256, 128` (4)
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* 16-Bit HDR R Texture `4096, 2048, 1024, 512` (8)
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* 16-Bit HDR RGB Texture `4096, 2048, 1024, 512` (8)
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* 16-Bit HDR RGBA Texture `4096, 2048, 1024, 512` (8)
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* 16-Bit HDR R Cubemap `1024, 512, 256, 128` (4)
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* 16-Bit HDR RGB Cubemap `1024, 512, 256, 128` (4)
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- 16-Bit Shadow Texture `4096, 2048, 1024, 512` (8)
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- 16-Bit Shadow Cubemap `2048, 1024, 512, 256` (4)
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* 8-Bit 3D R Texture `256, 128, 64, 32` (4)
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* 8-Bit 3D RGB Texture `256, 128, 64, 32` (4)
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* 16-Bit 3D HDR R Texture `256, 128, 64, 32` (4)
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* 16-Bit 3D HDR RGB Texture `256, 128, 64, 32` (4)
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Documentation should provide guidelines on categories of Art Assets and the resolution of textures to use.
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Textures are identified by a 32-bit integer.
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- `8 bits` → the texture buffer
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- `24 bits` → the layer in the buffer
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Artists should be informed on the texture structure of the engine and its limitations.
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However, these principles should be followed in other game engines as these are
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guided by what is most efficient for typical GPU hardware.
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Materials are, for the most part, user-defined. Documentation should make the user aware of this.
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Material buffers will be a sequence of the Material Struct instances.
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They will at the very least contain the id of their shader.
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Types of materials:
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- Surface (Vertex & Fragment)
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- Opaque / Masked
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- Translucent (Forward)
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- Volume (Path Traced Volumetrics / Forward)
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- Light (Lighting Model)
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- Post-Process
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## Stages
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This is the set of stages for the graphics pipeline that runs every frame:
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Unless otherwise specified, each stage will be run on the GPU.
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- BVH
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- Octree `(8 Bpn, 64 bpn) [6-Layers ≈ 2.1MB]`
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- Leaf Size and Tree Depth should be calculated by the scene, constraints are as follows:
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- Min Object Size
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- Max Object Size
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- Scene Center
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- Scene Edge
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- Buffer has implicit locations due to the tree having 8 children.
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- Insertions and Updates are done on the CPU
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- Nodes
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- Start Index `int32`
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- Object Count `int32`
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- Objects
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- Buffer of Object IDs grouped by Octree Node
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- Leaf Culling
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- Starting at each Octree Leaf, traverse upwards.
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- Insert Visible Leaf IDs
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- Track using atomic buffer
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- Generate the Command Buffer for Culled Mesh LODs from the Visible Leaf Buffer
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- Track counts using atomic buffers
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- To avoid double counting due to the construction of the Octree output, we have some options
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- Ignore Leaf Instances based on occurrences of the mesh in the surrounding 8 Quadtree Leaves. This would require
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a bias towards a specific corner of the filter.
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- Perform a preprocessing step on the CPU to erase duplicate elements and fix the buffer continuity.
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- Let the duplicates be rendered.
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- Generate the Culled Object Buffer with the respective object IDs
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- Adjust Buffer Size using the counts
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- Insert by reusing the count buffer, clipped to only contain used meshes
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Debug View: Object ID, Mesh ID, LOD
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- Visibility
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- Buffer `(15 Bpp, 120 bpp) [1920x1080] ≈ 39.4MB`
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- Depth Buffer → `D24`
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- Visibility Info → `RGB32I`
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- R = Object ID
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- G = Mesh ID
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- B = Material ID
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- Regenerate the Command Buffer for Visible Mesh LODs
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- Regenerate the Culled Object Buffer
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Debug View: Visibility Buffer
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* G-Buffer Pass `(17 Bpp, 136 bpp) [1920x1080] ≈ 35.3MB`
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* Depth - Stencil → `D24_S8`
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* S → used to represent the lighting model.
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* Diffuse → `RGBA8`
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* A → Ambient Occlusion
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* Emission → `RGB8`
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* Normal → `RGB8`
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* Specular → `RGB8`
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* R → Roughness
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* G → Specularity (sometimes called the Metallicness)
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* B → Index of Refraction (IOR)
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Debug View: Depth, Stencil, Diffuse, Emission, Normal, Specularity
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- Generate Dynamic Shadows
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- Generate Dynamic Reflections (Optional)
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- SSAO (Optional)
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- Deferred Lighting Pass `(10 Bpp, 80 bpp) [1920x1080] ≈ 2 x 16.3MB + 8.3MB ≈ 24.6MB`
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- Depth Buffer → `D24`
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- Lighting Buffer → `RGB16` w/ Mipmapping
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- Stencil Buffer $rarr; `S8`
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- Apply Lighting Model
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Debug View: Shadows, Reflections, SSAO, Deferred Lighting
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We can combine all of these into one framebuffer:
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- Depth - Stencil → `D24_S8`
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- Visibility Info → `RGB32I`
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- Diffuse → `RGBA8`
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- Emission → `RGB8`
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- Normal → `RGB8`
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- Specular → `RGB8`
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- Lighting Buffer → `RGB16` w/ Mipmapping
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- One more slot left open for another
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* Forward Pass
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* BVH, Same as Above
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* LOD Selection, Same as Above
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* Translucent Materials
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* Dual Depth Peeling
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Debug View: Forward Mask
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- Post Processing
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- Depth of Field (Optional)
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- When enabled, the Visiblity Buffer, G-Buffer, and Deferred Lighting Pass will be double layered.
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- At this point the Lighting Buffers will be Flattened
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- Bloom (Optional) → Mipmap Blurring `(6Bpp, 48bpp) [1920x1080] ≈ 16.3MB`
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- Tonemapping (Optional)
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- HDR Correction
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