[Simh] PDP-11 Spacewar?

[Johnny Billquist]

On 2018-11-09 15:59, Paul Koning wrote:
> 
> 
>> On Nov 9, 2018, at 5:24 AM, Johnny Billquist <bqt at softjar.se> wrote:
>>
>> On 2018-11-09 10:18, Lars Brinkhoff wrote:
>>> Hello,
>>> This seems to be a Spacewar for PDP-11.  Written using the PALX cross
>>> assembler.  But what kind of display is it using?
>>> https://github.com/PDP-10/its-vault/blob/master/files/rjl/war11.3
>>
>> Suspect it might be this: http://www.computerhistory.org/visiblestorage/1970s-1990s/games-and-robots/arcade/
>>
>> CHM have one. Not sure exactly what display it used, but it's obviously a vector display.
> 
> I don't think so.  Look at function LINE, it's a typical "step through the dots that make up a vector" algorithm.  Not Bresenham I think but something along those lines.

It don't look so much like stepping through dots, as small sections of 
line. It has a step value, which is 200, and it finds which is the 
smaller of delta x and delta y, and apply the 200 to that one, and 
figures out how much the other axle should change for each step, and 
then it loops through setting the CSR X and Y to these discrete values.

But maybe the resolution in the screen is so high that 200 really is 
just one pixel?

The code is written in a little cryptic fashion, by the way. It takes 
some reading. Not to mention the lack of comments...

   Johnny


-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol