glfract

This is an experimental program to explore Mandelbrot fractal set images.

The fractals are computed on the GPU using one of the following precisions:

• single precision
• extended precision based on 2x single precision
• double precision
• extended precision based on 2x double precision

The main feature are the 2x single or double precision modes, but unfortunately these do not work with many OpenGL implementations.

• Known to work:
  • Mesa 11.0 i965 on Sandybridge Mobile
  • Mesa 11.0 llvmpipe (LIBGL_ALWAYS_SOFTWARE=1)
  • Mesa 18.1.3 llvmpipe (LIBGL_ALWAYS_SOFTWARE=1)
  • Mesa 18.1.3 softpipe (LIBGL_ALWAYS_SOFTWARE=1 GALLIUM_DRIVER=softpipe)
• Known not to work:
  • Mesa 11.0 i965 on Bay Trail (strange artifacts)
  • Mesa 18.1.3 i965 on Kaby Lake U (strange artifacts, same as above)
  • NVIDIA proprietary drivers, any version (no additional precision; apparently the driver ignores the precise keyword from GL_ARB_gpu_shader5)

Coloring is based on user-defined color maps (e.g. created with gencolormap) and can be animated.