optix_prime_baking

This sample shows how to precompute ambient occlusion with OptiX Prime, and store it on the vertices of a mesh for use during final shading with OpenGL. Also see the accompanying Gameworks blog article.

Requirements

• A recent version of Visual Studio (tested with VS 2013 on Windows 7) or gcc (tested with gcc 4.8.4 on Ubuntu 14.04)
• CUDA 7.5+ and matching driver with supported GPU.
• A recent version of CMake (tested with 3.11.0).
• OptiX 3.9.0 from the shared_optix git repo (see below). If you have a Pascal or newer gpu, you will need to install a more recent OptiX SDK separately.
• On Linux, GLFW (tested with 3.2.0).

How to Build & Run

Quick build instructions:

Optional: Download and install the latest version of the OptiX SDK

1. Clone the following nvpro-samples repositories:

• //github.com/nvpro-samples/build_all.git
• //github.com/nvpro-samples/shared_optix.git (skip this if you already installed the OptiX SDK separately)
• //github.com/nvpro-samples/shared_sources.git
• //github.com/nvpro-samples/shared_external.git
• //github.com/nvpro-samples/optix_prime_baking.git

2. Download and install a recent version of CMake

3. Linux only: download and install GLFW.

4. Open CMake-gui (Windows) or ccmake (Linux):

• Source code to: /nvpro_ samples/build_all
• Build folder: /nvpro_samples/build_all/build
• Optional: set OPTIX_LOCATION to an external install of the OptiX SDK. Remove or hide any existing "shared_optix" directory.
• Optional: toggle MODELS_DOWNLOAD_DISABLED to download extra scenes during the configure step.
• Configure and select a compiler if prompted.
• Generate

5. Open the nvpro_samples.sln into Visual Studio, and Build All. On Linux, 'make' in the build directory.

6. Select the optix_prime_baking sample as the Startup project in VS.

7. Click Run in VS, or run the 'nvpro_samples/bin_x64/optix_prime_baking' binary in Linux.

The sample is configured on the command line; use the "-h" flag to list options or check main.cpp. The options at the time the sample was created are shown below:

App options:
  -h  | --help                          Print this usage message
  -f  | --file <scene_file>             Specify model to be rendered (obj, bk3d, bk3d.gz, csf, csf.gz).
  -o  | --outfile <vertex_ao_file>      Specify raw file where per-instance ao vertices are stored (very basic fileformat).
  -i  | --instances <n>                 Number of instances per mesh (default 1).  For testing.
  -r  | --rays    <n>                   Number of rays per sample point for gather (default 64)
  -s  | --samples <n>                   Number of sample points on mesh (default 3 per face; any extra samples are based on area)
  -t  | --samples_per_face <n>          Minimum number of samples per face (default 3)
  -d  | --ray_distance_scale <s>        Distance offset scale for ray from face: ray offset = maximum scene extent * s. (default 0.01)
        --ray_distance <s>              Distance offset scale for ray from face: ray offset = s. (overrides scale-based version, used if non zero)
  -m  | --hit_distance_scale <s>        Maximum hit distance to contribute: max distance = maximum scene extent * s. (default 10)
        --hit_distance <s>              Maximum hit distance to contribute: max distance = s. (overrides scale-based version, used if non zero)
  -g  | --ground_setup <axis> <s> <o>   Ground plane setup: axis(int 0,1,2,3,4,5 = +x,+y,+z,-x,-y,-z) scale(float) offset(float).  (default 1 100 0.03)
        --no_ground_plane               Disable virtual ground plane
  -w  | --regularization_weight <w>     Regularization weight for least squares, positive range. (default 0.1)
        --no_least_squares              Disable least squares filtering
        --no_viewer                     Disable OpenGL viewer
        --no_gpu                        Disable GPU usage in raytracer
        --conserve_memory               Triggers some internal settings in optix to save memory
        
Viewer keys:
   e                                    Draw mesh edges on/off
   f                                    Frame scene
   q                                    Quit

Supported scene formats

Loaders are provided for OBJ, Bak3d and CSF (basic cad scene file format used in various nvpro-samples). The OBJ loader flattens all groups into a single mesh. The bk3d/csf loaders preserve separate meshes, as shown in the teaser image above of a rocket sled with 109 meshes. Use the utilities in the Bak3d repo to convert other formats, or write a new loader for your favorite format and add it to the "loaders" subdirectory.

The rocket sled .bk3d file is automatically downloaded depending on MODELS_DOWNLOAD_DISABLED in the cmake config.

Output format

The sample uses a very basic format, that allows storage of the per-instance vertex-AO values in a binary file.

{
  uint64_t num_instances;
  uint64_t num_vertices;
  
  struct Instance {
    uint64_t storage_identifier;  // set by loader
    uint64_t offset_vertices;     // at which index to start in vertex array
    uint64_t num_vertices;        // how many ao vertex values used by instance
  } instances[num_instances];
  
  float ao_values[num_vertices];  // one value per vertex
}

Support

For general OptiX help, please join the NVIDIA Developer Program and download the full OptiX SDK, then post on the OptiX forums or mailing list.