Difference between revisions of "CRT shaders"

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(Tweaking CRT Geom)
(CRT Monitor variant)
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vec3 dotMaskWeights = mix(<br />vec3(1.0, 0.7, 1.0),<br />vec3(0.7, 1.0, 0.7),<br />floor(mod(mod_factor, 2.0))<br />);<br />mul_res *= dotMaskWeights;
 
vec3 dotMaskWeights = mix(<br />vec3(1.0, 0.7, 1.0),<br />vec3(0.7, 1.0, 0.7),<br />floor(mod(mod_factor, 2.0))<br />);<br />mul_res *= dotMaskWeights;
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=====Variants=====
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===CRT Geom===
 +
  
 
===CRT Monitor variant===
 
===CRT Monitor variant===

Revision as of 19:36, 22 July 2013

crt-geom-flat

Download

https://github.com/libretro/common-shaders/tree/master/crt

Overview

These replicate aperture grille CRTs, which have sharp images and strong scanlines. If you find that this doesn't look a damn thing like your old TV, it's probably because you owned a shadow-mask style CRT, which has less noticeable scanlines (the easiest way to tell the difference is to feel the curve of the screen; aperture grilles only curve horizontally if at all). Unfortunately, shadow masks require resolutions of upwards of 3000x4000 to emulate accurately, so all we have for the time being are aperture grille shaders.

Use integer scaling. This means either using windowed mode (x2,x3,x4) or setting an integer scaling option in the video options. The reason is that non-integer scaled scanlines will result in uneven lines with artifacts.

CRT Geom

One of the more popular CRT shaders.

Tweaking CRT Geom

You can open up CRT Geom in notepad and edit it.

Scanlines

vec4 weights = vec4(distance / 0.3); Raise the 0.3 to a higher value to make the scanlines brighter. I do not recommend going past 0.4, as at that point on bright colors scanlines completely disappear, and going further makes them appear again, but on the wrong field in said bright colors, which is inaccurate. Try 0.35.

Curvature

To make it flat, just set cornersize (line 107) to something small, like 0.001 and cornersmooth (line 110) to something large, like 8000.0. Then, comment out (i.e., put two slashes in front of it, like this: // ) line 141, #define CURVATURE.

Define Curvature. Something like that Comment it out. That means adding "//" in front of it. It should look like this when you're done:
//#Define Curavture

Interlacing

For the original, to disable interlacing, change this line:
ilfac = vec2(1.0,floor(rubyInputSize.y/200.0));
to the following:
ilfac = vec2(1.0,1.0);

Phosphor

To disable phosphor emulation (which alternately tints pixels green and magenta), comment out the following lines, found at the bottom of the shader code:

vec3 dotMaskWeights = mix(
vec3(1.0, 0.7, 1.0),
vec3(0.7, 1.0, 0.7),
floor(mod(mod_factor, 2.0))
);
mul_res *= dotMaskWeights;

Variants

CRT Geom

CRT Monitor variant

If you're using a CRT monitor, you can use these variants of CRT-Geom at 1280x960 full screen for an authentic 240p look. These variants are based on the flat variant with phosphor code commented out and the gamma correction disabled. There are three main variants (Normal, Sharp, Sharper), and each have different scanline brightness presets and interlacing enabled/disabled. As above, use integer scaling and force 4:3 aspect ratio. Some games may have black borders due to the full overscan area being visible, use your monitor's zoom function to zoom in and hide overscan. Also works with handheld games if you use the non-interlaced variant and force a 4x scale in RGUI.