Additional glsl shaders for cnc-ddraw ported from libretro slang repository
RetroArch moved from glsl to slang as their format of choice for shaders. Many new shaders were introduced into slang repository and some were updated compared to glsl repository. In order to use those shaders with cnc-ddraw, they must be converted to glsl format by hand.
Additionally some shaders can be tuned, cnc-ddraw currently can't change those parameters directly, files must be edited by hand. For example if you look at cubic/bicubic.glsl shader, you will notice at top of the file:
#pragma parameter B "Bicubic Coeff B" 0.33 0.0 1.0 0.01
#pragma parameter C "Bicubic Coeff C" 0.33 0.0 1.0 0.01
Those four numeric values beside parameters correspond to: default value, min value, max value, increments/precision. To actually change those values, look further down the file.
#ifdef PARAMETER_UNIFORM
uniform COMPAT_PRECISION float B, C;
#else
#define B 0.3333
#define C 0.3333
#endif
Adjusting those values will impact how shaders behaves. Provided cubic/bicubic-tuned.glsl has B/C values changed to 0.0/1.0 resulting in much sharper image at cost of potential ringing artifacts.