ZDoom 2.8.1 Partial Invisibility

[Xerge]

Hello everyone, I've got a question. I've noticed that when being Invisible in ZDoom every weapon sprite is animated like in the originals except for the Plasma Rifle which is static for some reason, does anyone know why this happens? Does it happen to anyone else or does anyone know how to fix it?

[scifista42]

It's actually animating normally, it's just hard to notice with invisibility on, because the outlines of plasmagun's firing frames are very similar to each other.

[Xerge]

Hi scifista, actually I am refering to the partial insivibility effect animation on the weapons, not to the firing frames of the weapons. You know what I mean? By the way, I recently played some wads you recommended to me on a thread I started a few months ago, really digged 'Lunatic'.

[Edward850]

Xerge said:

Hello everyone, I've got a question. I've noticed that when being Invisible in ZDoom every weapon sprite is animated like in the originals except for the Plasma Rifle which is static for some reason, does anyone know why this happens? Does it happen to anyone else or does anyone know how to fix it?

This actually isn't a bug (not in the way you're thinking, anyway), but requires understanding the semantics of the invisibility effect. Its animation isn't directly intended, rather it occurs because there's a global offset used for each pixel shifting set. How much onscreen uses the partial invisibility effect actually changes where this offset is at the start of each frame, thus creating an "animation effect" as each frame will shift the pixels starting at a different position.

Sans one edge case, where if the exact number of pixels on screen puts the offset into the same position each draw, and no animation is perceived. It's shifting the pixels the exact same way each time the scene draws. This is also why some sprites will appear to animate faster than others; it's all based on that static offset. If you were to throw a specter into the scene the effect will change again, as it'll also change the offset.

This effect is also resolution dependent, as it's a per pixel effect. Hence why the plasma rifle exhibits the issue. If you were to change the screen size, the effect changes with it.