Possible bug in glow-trails0.slang

[omx5o]

It appears to me that there is a bug in the vector-glow shader.

In the file glow-trails0.slang is the line:

float luma   = (frame.rrr * yiq_mat).r;

I believe that frame.rrr should be frame.rgb to calculate the correct luminance based on the rgb values.

This certainly improves the shader for me.

[hizzlekizzle]

It's been a loooong time since I worked on that, but I think my reasoning was that only the red phosphors have long enough decay times to be perceptible. Blue and green are both on the order of a few ms.

You like it better with RGB, though? what does that get you? If it looks better, I'm receptive to changing it.

[omx5o]

Ah, I see. That makes sense. I just tried comparing both again and you're right, it is better as it is.

Just out of interest, I also tried changing the second blur pass in vector-glow to a 43 size instead of 9 and that looked really good when playing Star Wars in particular. It's obviously more expensive but modern hardware like the Pi 5 can cope really well with it.

And along with that change I use the following parameter settings to get some really good results.

#reference "slang/crt/crt-effects/vector-glow.slangp"
mixfactor = "0.12"
threshold = "0.20"
trail_bright = "0.05"
screen_combine = "0.00"
haze_strength = "0.50"
ia_monitor_gamma = "2.40"
ia_saturation = "1.30"
ia_luminance = "2.00"

Thanks!