Real-time Rendering of Pre-integrated Neural Emitters

CV NeRF 3DGS
由具有遮挡结构的非平凡发光体、高面数自发光网格、空间变化的辐射特性,或可变形组件所引发的直接光照,一直是实时渲染中长期存在的性能瓶颈。当前的实时渲染方案要么依赖于简化的解析模型,要么退而采用运行时采样方法:解析方法仅适用于几何结构简单的发光体;纯基于采样的估计器则需极高的采样预算才能消除噪声;而代理表示法(proxy representations)仍需在运行时对发光体周围的出射辐射度进行积分计算。本文提出“神经发射场”(Neural Emission Fields, NEF),该表示法通过预先计算发光体周围空间中的光照信息,彻底消除了运行时积分开销。该神经场以空间位置、表面法线、观察方向及材质参数为输入变量进行参数化建模;借助一种双分支结构(分别处理漫反射与镜面反射),它仅需对每个着色点执行一次网络前向推理,即可输出无噪声、无遮挡的直接光照结果。由于训练过程在发光体自身的局部坐标系下完成,因此训练所得的NEF可作为便携式光照资产,在不同场景中经刚性变换后重复使用。内部多次反射、自遮挡、空间变化的辐射特性以及几何形变等复杂现象,均被隐式编码进学习所得的表示之中,且不带来任何额外的运行时开销。
Direct illumination from non-trivial emitters with occluding housing, high-polygon emissive meshes, spatially varying emission, or deformable assemblies is a persistent bottleneck in real-time rendering. Current real-time solutions either rely on simplified analytical representations or fall back to runtime sampling. Analytical methods are restricted to simple emitter geometry, pure sampling-based estimators need high sampling budgets to be noise-free, and proxy representations still require runtime integration over outgoing radiance around the emitter. We present Neural Emission Fields (NEF), a representation that eliminates runtime integration by precomputing the illumination in the volume around the emitter. This neural field is parameterized by position, normal, view direction, and material parameters. Using a two-headed diffuse/glossy architecture, it yields noise-free unoccluded direct illumination from a single network evaluation per shading point. Because training is performed in the emitter's local frame, a trained NEF acts as a portable lighting asset reusable across scenes under rigid transforms. Internal interreflections, self-occlusion, spatially varying emission, and deformations are absorbed into the learned representation at zero additional runtime cost.
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