Forward Shading Pipeline前向渲染管线

Pipeline Overview管线概览

NeoX's primary rendering path is forward shading — every visible pixel evaluates its material and all affecting lights in a single pass. This is configured by forward_shading.render (the pipeline declaration XML). The new engine's shader grew from 285 to 502 lines with major new feature additions.

NeoX 的主要渲染路径是前向着色——每个可见像素在单次 Pass 中计算其材质和所有影响光源。这由 forward_shading.render（管线声明 XML）配置。新引擎着色器从 285 行增长到 502 行，新增了大量特性。

Vertex Shader Stage顶点着色器阶段

The vertex shader performs geometry transformation with support for GPU skinning (up to 90 bones with 4 weights, or 8 weights with GPU_SKIN_8_ENABLE), vertex animation, foliage imposter rendering, and special projection modes. Two new parameters were added: SV_VertexID and SV_InstanceID:

顶点着色器执行几何变换，支持 GPU 蒙皮（4 权重最多 90 根骨骼，或通过 GPU_SKIN_8_ENABLE 支持 8 权重）、顶点动画、植被 Imposter 渲染和特殊投影模式。新增了两个参数 SV_VertexID 和 SV_InstanceID：

01Transform Chain (New Engine)变换链（新引擎）

Fragment vs_main(Vertex input,
                  uint vertex_id   : SV_VertexID,    // NEW
                  uint instanceID  : SV_InstanceID) { // NEW
  #if IMPORT_FROM_UE4
    ApplyUE4Scale();  // scale compensation for UE4-exported assets
  #endif
  #if FOLIAGEIMPOSTER_ENABLED
    CommonVertex vert = TransformCommonVertexImposter(input, vertex_id, vert_inter);
  #else
    CommonVertex vert = TransformCommonVertex(input, vert_inter);
  #endif
  ApplyVertexOffsetLocal(vert, vert.position);
  SetupFragmentAfterLocalOffset(...);     // NEW intermediate setup step

  #if GPU_SKIN_ENABLE
    DoSkin(vert.blendWeights, vert.blendIndices, ...);
  #elif GPU_SKIN_8_ENABLE
    DoSkin(..., texcoord5, texcoord6, ...);  // NEW 8-bone skinning
  #endif

  float4 world_position = Transform(vert.world_mat, vert.position);
  ApplyCustomizedUV(frag, vert);           // NEW custom UV transform
  ApplyVertexOffsetWorld(...);
  SetupFragment(...);
}

02Special Projection Modes特殊投影模式

Pixel Shader Stage像素着色器阶段

The pixel shader is where all material evaluation and lighting happens. The flow follows a strict order:

像素着色器是所有材质计算和光照发生的地方。流程遵循严格顺序：

float4 ps_main(Fragment input, bool is_front_face : SV_IsFrontFace) : SV_Target0 {
  // 1. Setup
  Material mtl = (Material)0;
  View v;
  v.position = CameraPosition;
  v.direction = normalize(input.position_world - CameraPosition);
  v.distance = length(input.position_world - CameraPosition);

  // 2. Material setup (calls into material_*.hlsl)
  RawData raw_data = GetRawData(input);   // texture sampling
  SetupMaterial(input, raw_data, mtl);    // decode --> Material struct

  // 3. Lighting (calls into lighting.hlsl --> shading model)
  LightingResult result = Lighting(input, mtl, v);

  // 4. Compose final color
  float3 color = result.direct_diff + result.direct_spec
              + result.env_diff + result.env_spec
              + mtl.emissive;

  // 5. Tone mapping
  color = get_ACES_tone_mapping(color);

  return float4(color, opacity);
}

Lighting Loop — How Lights Are Evaluated光照循环 — 光源如何计算

Inside lighting.hlsl (1447 lines, new engine), the main lighting function iterates over all active lights. Point and spot lights are now unified under a single PunctualLighting() function with PunctualLightParams structs. Each light calls the active shading model's DirectLighting():

在 lighting.hlsl（新引擎 1447 行）中，主光照函数遍历所有活动光源。点光和聚光灯现在通过 PunctualLightParams 结构体统一到单个 PunctualLighting() 函数。每个光源调用当前着色模型的 DirectLighting()：

Special Modes特殊模式

Source Files源码文件

• built_in/forward_shading.hlslMain forward shader (502 lines, new engine) — vs_main + ps_main主前向着色器（502 行，新引擎）— vs_main + ps_main
• built_in/forward_shading.renderPipeline declaration XML — ~280 macros, 16 shading models, 9 new VF models管线声明 XML — 约 280 个宏，16 种光照模型，9 个新 VF 模型
• built_in/common/lighting.hlslLighting core (1447 lines) — light loop + shading dispatch (unified PunctualLighting)光照核心（1447 行）— 光源循环 + 着色分发（统一 PunctualLighting）
• built_in/common/rect_lighting.hlslNEW: Extracted area/rect light functions新增：提取的区域/矩形光函数
• built_in/common/ssss.hlslNEW: Extracted SSS transmittance functions新增：提取的 SSS 透射函数
• built_in/common/spherical_gaussian.hlslNEW: Bent normal SG math for AO occlusion新增：用于 AO 遮挡的弯曲法线 SG 数学
• built_in/shadow/shadow.hlslShadow map sampling — Render 3.0 CSM with sphere-cull cascade selection阴影贴图采样 — Render 3.0 CSM 带包围球 Cascade 选择
• built_in/common/decal.hlslDeferred decal application延迟贴花应用