add ui part one

Author: hazard-10

README.md

@@ -3,21 +3,75 @@ CUDA Path Tracer
 
 **University of Pennsylvania, CIS 565: GPU Programming and Architecture, Project 3**
 
-* (TODO) YOUR NAME HERE
-* Tested on: (TODO) Windows 22, i7-2222 @ 2.22GHz 22GB, GTX 222 222MB (Moore 2222 Lab)
+* Jiahang Mao
+  * [LinkedIn](https://www.linkedin.com/in/jay-jiahang-m-b05608192/)
+* Tested on: Windows 11, i5-13600kf @ 5.0GHz 64GB, RTX 4090 24GB, Personal Computer
 
-### (TODO: Your README)
+## 1. Key feature implemented
 
-1. Obj loading 2 / GLTF 4
-2. depth of field 2
-3. refraction 2
-4. direct lighting 2
-5. Russian roulette 1
+Part 1
+1. Cuda path tracing with lambertian and specular shading kernel
+2. Unhit path termination using Stream Compaction
+3. Sort ray-scene intersection by material type
+4. Stochastic sampled antialiasing
 
-1. GLTF 4
-2. BVH 6
+Part 2
+1. Obj mesh import.
+2. BVH. Tree construction done on CPU, traversal with GPU. Configurable with either max depth or max leaf size.
+3. Refraction. Support transmissive-only and glass-like material.
 
-### Build 
+## 2. Build 
 
-Use c++ 17 instead of 14, since I added < filesystem.h > to support importing files using windows file system.
+Use C++ 17 or later instead of default C++ 14 with VS2022. Reason is because I added `<filesystem.h>` to support importing files using windows file system.
+
+Change under property -> C/C++ -> Language -> C++ Language Standard
+
+![How to](img/clang_update.png)
+
+
+## 3. Navigating UI
+
+I made some updates to the UI, building on top of the imgui.
+
+![UI](img/UI.png)
+
+#### Mesh Options
+* `Centralize mesh` When loading loading arbitrary obj mesh, this option automatically compute the center and scale, then apply a transformation to the center of camera's front pov.
+* `Mesh transformation` Post-import transformation also customizable.
+#### Acceleration Structure
+A single choice between three options
+* `None` No accleration structure will be applied. For each render pass the intersection checks each ray against all geometry in the scene.
+* `Basic Bounding Volume Culling` Conceptually equivalent to a depth-equals-to-one BVH. Construct a single bounding box surrounding the mesh. 
+* `Bounding Volume Hierarchy` Construct a tree-like structure to organize the geometry. The tree is built on CPU and traversed on GPU.
+  ![UI](img/bvh_ui.png)
+  * `Bins to Split Per Axis` Controls the number of bins used when determining the best split plane during BVH construction.
+  * `BVH Constraint` Choose between using a maximum leaf size or maximum depth as the stopping criterion for BVH construction.
+    * `Max Leaf Size` The maximum number of primitives allowed in a leaf node.
+    * `Max Depth` The maximum depth allowed for the BVH tree.
+#### Render Options
+* `Use Path Tracing` Toggle between path tracing and basic shading. Latter suited for quick view of geometry.
+* `Sort by Material` Enable/disable sorting of ray-scene intersections by material type.
+#### Loading file
+* Support either .json or .obj file. When importing an obj file, automatically load a display room scene under ./scenes/display_room.json
+
+    ![UI](img/file_UI.png)
+#### Program output
+* Command prompt will have useful info about the mesh and bvh for debugging.
+    ```console
+    --- Mesh Info ---
+    Loaded 5664 vertices, 11272 faces, and 1 face materials.
+    Auto-centering object...
+    Geometric Center: vec3(0.108734, 0.431662, 0.382079)
+    Average Distance to center : 1.03667
+    --- BVH Info ---
+    Building BVH...
+    Validating BVH...
+    BVH is valid. Max depth: 50, largest leaf size: 69
+    ```
+## 4. Performance benchmark
+
+
+### 3rd-party code used
+
+* https://github.com/tinyobjloader/tinyobjloader/