P61

Image-Based Lighting (IBL)

P62

Basic Idea of IBL

对真实的环境光照做预处理，快速地计算环境光照与材质之间的卷积。
SH 的局限性：SH 的表达比较粗糙，只能有明暗的感觉，达不到场景细节感和凹凸感的效果。

P64

Diffuse Irradiance Map

根据上文可知，\(L_o（x，W_o）\) 可以分为 diffuse 项和 specular 项。 Diffuse 须提前把卷积结果算好存下来。实时渲染时查表即可。

P65

Specular Approximation

Specular 项的推导比较复杂，且做了大量假设和近似。
但 specular 结果与参数 roughness 有关。因此将不同 roughness 的结果存到了不同的 mipmap 中。因为，roughness 越大，对光的敏感度越低，可以放到 mipmap 的最低级。
方法详见 GAMES 201。

P66

Approximation: part (1/2)

P67

Approximation: part (2/2)

P68

Quick Shading with Precomputation

P69

Shading PBR with IBL

P70

Classic Shadow Solution

P75

Hard Shadow vs Realistic Shadow

P76

PCF - Percentage Closer Filter

  • Target problem
    • The shadows that result from shadow mapping aliasing is serious
  • Basic idea
    • Sample from the shadow map around the current pixel and compare its depth to all the samples
    • By averaging out the results we get a smoother line between light and shadow

用滤波的法做软阴影。

P77

PCSS - Percentage Closer Soft Shadow

  • Target problem
    • Suffers from aliasing and under sampling artifacts
  • Basic idea
    • Search the shadow map and average the depths that are closer to the light source
    • Using a parallel planes approximation

P78

Variance Soft Shadow Map

  • Target problem
    • Rendering plausible soft shadow in real-time
  • Basic idea
    • Based on Chebyshev‘s inequality, using the average and variance of depth, we can approximate the percentage of depth distribution directly instead of comparing a single depth to a particular region(PCSS)

P79

光：Lightmap + Light probe
材质： PBR + IBL(环境光)
阴影：Cascade shadow + VSSM

P80

Moving Wave of High Quality

P81

Quick Evolving of GPU

  • More flexible new shader model
    • Compute shader
    • Mesh shader
    • Ray-tracing shader
  • High performance parallel architecture
    • Warp or wave architecture
  • Fully opened graphics API
    • DirectX 12 and Vulkan

P82

Real-Time Ray-Tracing on GPU

P83

Real-Time Global Illumination

Screen-space GI
SDF Based GI
Voxel-Based GI（SVOGI/VXGI）
RSM / RTX GI

P86

Shader Management

P90

Uber Shader and Variants

A combination of shader for all possible light types, render passes and material types

  • Shared many state and codes
  • Compile to many variant short shaders by pre-defined macro

利用 uber 写好少量 shader 模版，然后自动生成大量 shader.

P92

Cross Platform Shader Compile