DPC+ bB 1.1 Still flickers virtual sprites on same scanline?

[+Gemintronic]

My copy of bB 1.1 with VisualbB may be broke as it never compiles the msdpc.bas example. Regardless, I wondered if anyone could clarify if virtual sprites still flicker or dissappear when on the same scanline?

 

If so, what is real the advantage of having all those virtual sprites if they can't exist nicely on the same horizontal row?

 

What are some techniques to mitigate this issue?

Edited June 19, 2012 by theloon

[+RevEng]

The virtual sprites flicker when they're on the same row. While there are tricks to allow for a player to be repeated on a line - like player copies and RESP tricks - they don't allow for completely independent positioning, so they aren't suitable for a general purpose multisprite kernel.

 

The real advantage of the multisprite/DPC+ kernels is that the virtual sprites don't flicker when they have enough vertical separation.

 

Think of pacman 2600, which was coded with a constant flicker routine for the ghosts, with each ghost being displayed 1/4 of the time.

 

Most of the time all 4 of the ghosts don't share the same horizontal slice. If pacman 2600 had been coded with a multisprite routine, often the ghosts would be displayed 1/2 or 1/3 of the time, and sometimes they wouldn't flicker at all. You could even go a step further and modify the AI for the ghosts so they prefer to be on different horizontal sections of the maze, which would reduce flicker even more.

 

It should be mentioned that you can design vertical separation into your game. Jrok's Santa's Scabs game (part of "The Byte Before Christmas" multicart) uses the bB multisprite kernel and a clever design to achieve a game with lots of moving elements and no flicker...

 

 

Virtual players are used for the marching elves, the boss elf, and the timer light on the house.

[+Gemintronic]

One thing I haven't noticed (at least in bB games) is combining multiple vertical sprites into one. This could work for, say, Final Fantasy type games where you have four characters.

 

All these dudes could be Sprite0:

 

\(^_^)/

 

/(o_o)\

 

-('_')-

 

_(x_x)_

 

Thus, you could have multiple virtual sprites facing your party vertically without flicker. In theory

 

Oh! And, I think I remember the old bB multi-sprite kernel needing at least 2 lines of separation to avoid flicker. Is 2 lines the rule?

 

Clever use or should I say making the illusion of no vertical flicker limitation seems to be the key. I've attached a screenshot of my Project26/Sensational Santucci Sisters smooth horizontal scrolling demo. The player is sprite0. Notice the grey vertical "chip" object doesn't quite reach the floor. It's long enough to register as a wall or blockage but short enough for the red enemy to pass freely (and without flicker.)

Edited June 19, 2012 by theloon