第四节：游戏引擎中的渲染实现

渲染概述

Challenges on Game Rendering

1. Complex render objects

2. Deal with architecture of modern computer with a complex combination of CPU and GPU

3. Commit a bullet-proof framerate,

   1. 30 or 60 or 120 fps

   2. HD, 1080p, 4k, 8k

4. CPU memory

Rendering on Game Engine

A heavily optimized parctical software framework to fulfill the critical rendering requirements of games on modern hadware

Outline of Rendering

1. Basics of Game Rendering

   • Hardware architecture

   • Render data organization

   • Visibility

2. Materials, Shaders and Lighting

   • PBR

   • Shader permutation

   • Lighting

   • Point / Directional lighting

   • IBL / Simple GI

3. Special Rendering

   • Terrain

   • Sky / Fog

   • Postprocess

4. Pipeline

   • Forward, deferred rendering forward plus

   • Real pipeline with mixed effects

   • Ring buffer and V-Sync

   • Tiled-based rendering

渲染系统的对象

Building Block of Rendering

image-20220413212212448

image-20220413212321697

image-20220413212331478

Computation - Texture Sampling

昂贵的三线性滤波，采样 8 个像素点，7 次滤波

1. Use tow nearest mipmap levels

2. Perform bilinear inerpolation in both mip-maps

3. Linear interpolate between the results

GPU 架构

The dedicated hardware to solve massive jobs

SIMD and SIMT

• SIMD 单指令多数据

image.png

• SIMT 单指令多线程

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GPU Architecture

架构和不同核心

image-20220413212419569

数据流动

cpu 到 gpu 的高延迟

image-20220413212434311

多级缓存，数据尽量要放在一起

image-20220413212513383

GPU Bounds and Performance

• Memory Bounds 内存瓶颈

• ALU Bounds 计算瓶颈

• TMU (Texture Mapping Unit) Bound 纹理采样瓶颈

• BW (Bandwidth) Bound 数据传输瓶颈

image-20220413212550528

image-20220413212555358

Renderable

可绘制的东西

• Mesh Render Component

• Building Blocks of Renderable

• Mesh Primitive

  • struct Vertex

    • position

    • color

    • normal

  • struct Triangle

    • Vertex[3]

• Vertex and Index Buffer

  • Vertex Datda

  • Index Data

  

  image-20220413212626112
• We Need Per-Vertex Normal

• Materials
• Material Model
• Various Textures in Materials

• Variety of Shaders

Render Objects on Engine

• Coordinate System and Transformation

• Object with Many Materials

• Resource Pool

  • Use Handle to Reuse Resources

    

    image-20220413213129463

    

    image-20220413213209476
• Instancing 实例化，前边的都是物体绘制的定义，实际上绘制到屏幕上才是实例

• Sort by Material

• GPU Batch Rendering

  

  image-20220413213223322

Visibility Culling 可见性裁剪

• Culling One Object

  • View Frustum

  • Bounding Box

  • Hierarchial View Frustum Culling

  • Construction and Insertion of BVH in GameEngine

    • BVH 在动态物体多的情况下构建成本低

    • PVS (Potential Visibility Set) 对于空间上的一点关于其他物体的潜在可见性，即是否不会被其他物体遮挡

    • The Idea of Using PVS in Stand-alone Games

  • GPU Culling

    • Depth pre pass / early z 提前渲染深度到 z buffer，防止重复像素点着色

Texture Compression

纹理压缩

• Traditional image compression like JPG and PNG

• In game texture compression

  • 需要支持随机访问

• Block Compressions

  • Common block-based compression format

  • On PC BC7 or DXTC

  • On mobile, ASTC or ETC

Authoring Tools of Modeling

• Modeling

  • Polymodeling : MAX, MAYA, Blender 网格建模

  • Sculptiong : 雕刻

  • Scanning : 扫描

  • Procedural Modeling : 程序化生成

Cluster-Based Mesh Pipeline

• Sculpting Tools Create Infinite Details 无数的细节

• GPU-Driven Rendering Pipeline

• Geometry Rendering Pipeline Architecture

• Programmable Mesh Pipeline

• Mesh shader, cluster base mesh

  

  image-20220413213322563
• GPU Driven

  • 把越来越多 CPU 上的计算放到 GPU 上做

PILOT

小引擎项目 https://github.com/BoomingTech/Pilot