Guided Visibility Sampling++

Paper link

This repository contains the reference implementation of our GVS++ visibility algorithm. The main parts of the algorithm are implemented in the shaders raytrace.rgen (random sampling), raytrace_abs.rgen (adaptive border sampling), and reverse_sampling_new.rgen (reverse sampling).

Requirements

The application was developed using the following libraries (note that the code may also compile wither newer library versions):

• Vulkan SDK 1.2.135.0
• GLFW 3.3.2
• GLM 0.9.9.7
• tinyobjloader 1.0.7

The library paths are set in CMakeLists.txt.

Usage

Parameters

The settings file (--- SETTINGS --- section in the file) contains various parameters that control the behavior of the algorithm. Various parameters that control the number of samples that are used can be set. These parameters can be used to fine-tune the algorithm for specific scenes, if necessary. We found that a standard set of parameters performs well for all tested scenes and view cell placements.

Random Sampling

• RANDOM_RAYS_PER_ITERATION, the number of random rays/samples used during one iteration of random sampling, e.g. 10000000.

Adaptive Border Sampling (ABS)

• ABS_DELTA, the distance of the enlarged polygon to the original triangle, e.g. 0.001.
• ABS_NUM_SAMPLES_PER_EDGE, the number of samples along each edge of the enlarged polygon, e.g. 40.

Reverse Sampling (RS)

• REVERSE_SAMPLING_NUM_SAMPLES_ALONG_EDGE, the number of samples along each edge of the view cell for the reverse sampling, e.g. 40.
• REVERSE_SAMPLING_HALTON_NUM_HALTON_SAMPLES, the number of samples on the view cell for the reverse sampling, e.g. 40.

Termination

The termination of the PVS search can be controlled via two parameters: GVS++ terminates if less than NEW_TRIANGLE_TERMINATION_THRESHOLD new triangles have been found during the last NEW_TRIANGLE_TERMINATION_THRESHOLD_COUNT iterations.

View Cell

• USE_3D_VIEW_CELL true/false
  • true: Use 3D view cells.
  • false: Use 2D view cells.

Visualization

• COMPUTE_ERROR true/false
  • true: Calculate and print pixel error, and render the whole scene in red and the PVS in green.
  • false: Only render the PVS.
• FIRST_RAY_HIT_VISUALIZATION true/false
  • true: Visualize rays that discovered new triangles (toggle with T).

Scene Specification

The scene and the file in which the resulting PVS is stored is also specified in the settings file (--- SCENE --- section in the file).

Example:

--- SCENE ---
CALCPVS pvs.txt
CITY
SPECIFY_VIEW_CELL_CENTER false

• CALCPVS specifies that the PVS is calculated and stored in pvs.txt. Alternative are CALCPVS_NOSTORE, where the PVS is only calculated, and LOADPVS, where the PVS is loaded from the specified file.
• CITY is the name of the scene for which GVS++ is executed.
• SPECIFY_VIEW_CELL_CENTER specifies whether the position of the view cell (see below) defines the center or bottom left corner of the view cell.

Scenes and view cells are specified in the scenes file. Example:

CITY models/city.obj
30 3 150
40 50 150
0 0
-135 3 40
40 50 165
0 90

• CITY is the name of the scene followed by the location of the obj file.
• The view cell specification contains the position (30 3 150), size (40 50 150) and rotation around the x- and y-axis (0 0). Multiple view cells can be specified as in the example above. In this example, 3D view cells are used, therefore USE_3D_VIEW_CELL = true has to be set.

Key bindings

View Cells

• C switch to the next view cell.
• F cycle through the corners of the current view cell.

Visualization

• G toggle rendering of a mesh that represents the current view cell.
• V toggle model shading.
• T toggle ray visualization (only if FIRST_RAY_HIT_VISUALIZATION true is set).

Camera and Mouse

• Esc release the mouse.
• Q print camera position.
• 1/2 decrease/increase camera movement speed.
• W, A, S, D, Space, Shift move camera.

Miscellaneous

Vulkan validation layers can be enabled in GLFWVulkanWindow.h.