This time i talk a bit retro. This is nothing you want to use in actual games. At Egosoft we’ve an Arcade Machine with titles like 1943 (not Battlefield 1943 ;) ) and i really like how they faked their transparent shadows.
What do you do, if you can’t use “real” transparency? Stunts just didn’t render every 2nd pixel:
Source: Dakksters Blog
1943 used another approach. They rendered the solid shadow of the airplane only every 2nd frame. I’m sorry for the low FPS of the Gif, it looks better at the Arcade Machine. Because there you’ve a higher frame rate and the illusion works better. But the video i recorded didn’t work so well, this is why i faked the fake in Photoshop.
Airplane by Chris Ensell
I didn’t embed the video directly to avoid any tracking from Google and complications with the DSGVO.
the stunts apporach is almost the same thing we call apha to coverage now
When we started working with DirectX some graphics chips had the ability of “stippled alpha”, which basically was rendering only each second pixel, exactly what you showed in the “Stunts” screenshot. This had the advantage that the destination pixel didn’t have to be read to do a true alpha blend.
The 1942 effect is enhanced because of interlacing (ie every other line is render every other frame), since it get “mixed” by the CRT. This is only possible if it runs on 50/60Hz, but hardware could easily aid sprites to only be shown on eg odd frames. So if you did everything right you wouldn’t just get “free temporal smoothing” but also twice the vertical resolution with “super-sampled anti-aliasing”.
Thanks for your comment and sharing those information with us :) Yes these old analog displays have you also free motion blur because the surface had a slight after-glow-effect :D