NVIDIA RTX and DirectX Ray Tracing

转自：https://developer.nvidia.com/blog/introduction-nvidia-rtx-directx-ray-tracing/?utm_source=wechat_session&utm_medium=social&utm_oi=982728699078164480

rtx raytracing 

加速结构：

API: BuildRaytracingAccelerationStructure().

分两种加速结构

1.底层加速结构

如三角形

 Bottom-level acceleration structures are built from geometric primitives, such as triangles. The input primitives for these builds are specified through one or more geometry descriptors. A geometry descriptor includes a vertex and an index buffer, making its granularity roughly comparable to a draw call in rasterization.

2.高层加速结构

索引节点，包含transform matrix 和 material索引

Top-level acceleration structures in turn are built from references to bottom-level structures. We call these references instance descriptors. Each instance descriptor also includes a transformation matrix to position it in the scene, and an offset into the shader table to locate material information (see below). Notice that in our ray generation shader example earlier, the ‘scene’ parameter to TraceRay() was a top-level acceleration structure — it represents the “entry point” of the intersection search.

Shader table

每个object 属性有一个shader record 表示，Shader table 存储场景中所有物体的shader record