Overview

Our I3D 2015 paper targets real-time subpixel accurate hard shadows. Highlights include:

• Avoids spatial and temporal aliasing common in shadow maps.
• Only needs a single world-space epsilon, equivalent to the epsilon used in ray tracing to avoid self-shadows.
• Under 20 ms for 32 sample per pixel shadows (and < 10 ms for 1 sample per pixel) on multi-million polygon game-quality scenes.
• Based on a fast formulation of irregular z-buffers.
• Finds a duality between shadow map aliasing and irregular z-buffer performance (i.e., cascades improve performance, not quality).
• No assumptions on input geometry. (Performance reported on triangle soup, with no frustum culling or any geometric annotation.)

Our project explicitly targets only hard shadows. We expect screen-space blurs or PCSS style soft shadow approximations could be used with our improved input signal rather than a shadow map. Future work will explicitly explore more accurate soft shadows.

Demo

Currently, we provide only a binary demo. Source code may follow at a future date. The executable download should have everything you need to run the demo on a number of fairly simple scenes. Additional, more complex models are available as separate downloads:

• Windows executable (28.2 MB)
  • Note: Early Windows 10 drivers had issues running this demo. See requirements, below.
• Additional scenes:
  • The 2.9 million polygon hairball model (37.1 MB)
  • The 12.3 million polygon UNC powerplant model (66.3 MB)
  • The 0.8 million polygon LordGood model (10.2 MB) (from Martin Mittring's shadow demo)
  • The 6.7 million polygon Rungholt model (71.7 MB)
  • The 3.8 million polygon tentacles model (63.1 MB)

Requirements

Our algorithm has been tested on NVIDIA and AMD hardware. However due to focusing optimization efforts on our hardware, this demo requires an NVIDIA GPU. More explicit requirements:

• A Maxwell or newer GPU for full hardware acceleration (i.e., a Titan X or GeForce GTX 9xx)
  • NVIDIA Kepler GPUs (GeForce GTX 7xx and many 6xx) are supported via only slower software conservative rasterization
• NVIDIA driver version:
  • On Windows 10, earlier drivers did not work. Working versions include 391.xx and later.
  • On Windows 7 or 8.1, you can use driver 352.86 or higher
  • For Kepler GPUs, drivers later than 350.xx should work; we still recommend 352.86.
• A 64-bit version of Windows. We've tested on Windows 7, 8.1, and 10.
• Full GPU acceleration requires driver support for the following OpenGL extensions:
  1. NV_conservative_raster
  2. NV_geometry_shader_passthrough
  3. NV_shader_buffer_store
  4. NV_viewport_array2
  5. NV_conservative_raster_dilate

Running the Demo

Details for controls and caveats are in the demo's README file.