From BlenderWiki
Source Code Layout
The source code is organized into folders as follows:
| app/ | Standalone session and network rendering server applications. |
| blender/ | Python module and C++ extension to integrate with Blender. |
| blender/addon | Python scripts for the Blender addon. |
| cmake/ | Build and release files. |
| bvh/ | Bounding volume hierarchy constructions for raytracing. |
| device/ | Device abstraction for CPU, CUDA, OpenCL and network. |
| doc/ | Documentation, mostly in html code that is generated. |
| doc/license/ | Licenses. |
| kernel/ | Rendering kernel. |
| kernel/svm/ | Shader virtual machine to execute shader graphs on the CPU and GPU. |
| kernel/osl/ | OSL render services and shading engine, only runs on the CPU. |
| kernel/osl/nodes/ | OSL shaders used in the shader graph. |
| render/ | Main render engine data structures and control flow. |
| subd/ | Tesselation and subdivision surfaces. |
| test/ | Test suite. |
| util/ | Utility code. |
