Deferred Shading Pipeline延迟渲染管线

GBuffer LayoutGBuffer 布局

NeoX's deferred path uses a compact 3-RT GBuffer for the standard mode, or a 5-RT Single-Pass Deferred for mobile (TBDR) optimization. This is significantly simpler than UE5's 5+ RT layout.

NeoX 的延迟路径标准模式使用紧凑的 3-RT GBuffer，或为移动端（TBDR）优化使用 5-RT 单 Pass 延迟。这比 UE5 的 5+ RT 布局简单得多。

GBuffer Write — ps_main()GBuffer 写入 — ps_main()

The GBuffer pixel shader is remarkably simple — it just fills the Material struct and packs it into render targets:

GBuffer 像素着色器非常简洁——只需填充 Material 结构体并打包到渲染目标：

struct GBuffer {
  float4 AlbedoAO               : SV_Target0;
  float4 NormalRoughness         : SV_Target1;
  float4 MetallicShadingModelFlags : SV_Target2;
};

GBuffer ps_main(Fragment input, bool is_front_face : SV_IsFrontFace) {
  RawData raw_data = GetRawData(input);
  Material mtl = (Material)0;
  SetupMaterial(input, raw_data, mtl);
  DeferredApplyNewDecal(input, mtl);  // apply decals

  GBuffer gbuffer;
  gbuffer.AlbedoAO = float4(mtl.albedo, mtl.occlusion);
  gbuffer.NormalRoughness = float4(0.5 * (mtl.normal + 1.0), mtl.roughness);

  // Encode flags into single byte
  uint flags = 0;
  flags = EncodeShadingModel(flags, mtl.shading_model);
  flags = EncodeReceiveShadow(flags);          // if SHADOW_MAP_ENABLE
  flags = EncodeClusteredShadingLightProbeVolumeEnable(flags);

  gbuffer.MetallicShadingModelFlags = float4(
    mtl.metalness,
    float(flags) / 255.0,
    0, 0
  );
  return gbuffer;
}

Single-Pass Deferred — Mobile Optimization单 Pass 延迟 — 移动端优化

On tile-based deferred rendering (TBDR) GPUs (iOS/Android), NeoX supports Single-Pass Deferred Shading. This writes both GBuffer data AND lighting result in one pass, avoiding the costly off-chip GBuffer readback that destroys TBDR benefits.

在基于 Tile 的延迟渲染（TBDR）GPU 上（iOS/Android），NeoX 支持单 Pass 延迟着色。在一个 Pass 中同时写入 GBuffer 数据和光照结果，避免了破坏 TBDR 优势的昂贵离片 GBuffer 回读。

// Single-pass mode: output emissive directly + manual depth
#if SINGLE_PASS_DEFERRED_SHADING_ENABLE
  gbuffer.FinalResult = float4(mtl.emissive, 1);
  #ifdef NEOX_GLSL
    gbuffer.Depth = input.position.z;           // single float
  #else
    gbuffer.Depth = float4(input.position.z);   // packed
  #endif
#endif

Flag Encoding System标志位编码系统

The G channel of MetallicShadingModelFlags packs multiple boolean flags into a single byte (0-255). Defined in flags.hlsl:

MetallicShadingModelFlags 的 G 通道将多个布尔标志打包到单个字节（0-255）中。定义在 flags.hlsl：

NeoX vs UE5 GBuffer ComparisonNeoX vs UE5 GBuffer 对比