CRT-Royale

CRT-Royale, with default settings at 1080p (view original for full details)

CRT-Royale is a highly advanced multi-pass CRT shader that simulates almost every aspect of the CRT screen. There are tons of parameters to configure, such as phosphor type (aperture grille, slot mask, and EDP shadow mask) and size (i.e. dot pitch), convergence offsets, scanline blooming and many others. Higher resolution is better for this shader, especially with EDP shadow mask phosphor layout and with smaller phosphor dot pitch values. This shader is really complicated compared to most other CRT shaders, reading the README and the documentation in the user-settings.h is a must.

Customization

Since CRT-Royale has a large number of different settings for customization, this article will only cover those that have the most noticeable effect on the overall image.

CRT-Royale can be customized one of two ways: using the runtime shader parameters from inside RetroArch or editing the user-setting.h file. In order for the settings in user-settings.h that are marked with _static to take effect, runtime parameters must be disabled by commenting out #define RUNTIME_SHADER_PARAMS_ENABLE in user-settings.h. Doing this will make the runtime parameters non-functional so you will need to reload the shader to apply changes, but it will result in a performance boost since there is less need for expensive branching in the shader code when the settings are static.

There are some settings in user-settings.h that are static only and do not have a runtime parameter, and therefore do not require runtime parameters to be disabled to have an effect.

The settings listed below are taken from the runtime parameters with their default values.

Gamma and Contrast

crt_gamma = 2.500000
lcd_gamma = 2.200000
levels_contrast = 1.000000

Gamma and contrast controls. CRT gamma is the output gamma of the shader, while LCD gamma is the input gamma, which should be 2.2 in most cases.

Halation and Diffusion

halation_weight = 0.000000
diffusion_weight = 0.075000

Weights for halation and diffusion of the simulated CRT. Halation is the light being reflected on the phosphors, while diffusion is the light causing a glow when passing through the glass. Some may find these effects to be annoying, so they can be turned off by setting them to 0.0.

Bloom

bloom_underestimate_levels = 0.800000
bloom_excess = 0.000000

These settings control the level of blooming in the shader. Higher bloom_underestimate will cause the bloom to be more intense. bloom_excess causes extra blurring of all colors to soften the bloom effect, which is disabled by default.

Beam

beam_min_sigma = 0.020000
beam_max_sigma = 0.300000
beam_spot_power = 0.330000
beam_min_shape = 2.000000
beam_max_shape = 4.000000
beam_shape_power = 0.250000
beam_horiz_filter = 0.000000
beam_horiz_sigma = 0.350000
beam_horiz_linear_rgb_weight = 1.000000

These settings determine the shape and size of the lit scanlines of the simulated CRT.

Min and max sigma settings affect the size of each scanline relative to the brightness of the image. A large range of beam sigmas causes the scanlines to vary in width depending on brightness, while small ranges result in less variable width of scanlines. Higher sigmas increase the size of the scanlines, resulting in smaller gaps and more vertical blurring.

Min and max shape settings affect the Gaussian profile of the scanlines. Higher values for these make the scanline plateaus flatter and have steeper drop offs. These effects are really only noticeable at higher screen resolutions.

beam_horiz_filter specifies how the beam is filtered horizontally. The options are 0.0 (Quilez, sharp and fast), 1.0 (Gaussian, configurable sharpness), and 2.0 (Lanczos2, sharp and higher quality). beam_horiz_sigma is used to set the level of blur when using Gaussian horizontal filtering.

External Links

• CRT-Royale on GitHub
• CRT-Royale and 3dfx Shaders - hunterk's blog post about CRT-Royale's different phosphor mask layouts.