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Trip2018

Pfpixel used as missile?

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Posted (edited)

I kinda got to thinking, what if you could use pfpixel as a sort of fake missile. It would flip every frame and motion would be on the second frame.

Edited by Trip2018

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Activision's Chopper Command uses the playfield as the shots from the chopper. You can see that by using a Developer Key to turn on Stella's Fixed Debug Colors mode.

 

By referencing the color key on the TIA Tab of Stella's Integrated Debugger you can see that anything purple is drawn using the playfield.

 

post-3056-0-34775000-1559652369.png

 

post-3056-0-85491400-1559652754.png

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This sounds interesting. Doesn't the pfpixel have different kind of coordinates versus a missile x y coordinate?

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Posted (edited)

I was curious if I understand this correctly. Looking at the Activision logo, I see it is made from player0 and player1. I assume that is because of pixel width limitations for the Sprite. I was wondering about how they alternate. Is that deal with how the image is drawn on the screen so as to not flicker?

 

And as for using the pfpixel or playfield as a missile, would performing such an action provide a certain benefit, apart from freeing up a missile?

Edited by KevKelley

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I was curious if I understand this correctly. Looking at the Activision logo, I see it is made from player0 and player1. I assume that is because of pixel width limitations for the Sprite. I was wondering about how they alternate. Is that deal with how the image is drawn on the screen so as to not flicker?

That's the standard 48 pixel display that's normally used for drawing 6 digit scores. In this case it's used to draw the radar and logo.

 

And as for using the pfpixel or playfield as a missile, would performing such an action provide a certain benefit, apart from freeing up a missile?

The playfield is not used for anything else in that section of the screen, so using it for the player's shots allows it to have a color distinct from everything else. Also allows it to be significantly longer than the 8 pixel limit of a standard missile - this is what caused me to investigate how Activision did this game.

 

post-3056-0-18937600-1559657229.png

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I was thinking more along the lines of kicking shells in sprybug's princess rescue.

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The main issue I've had is using too much CPU time with the pfread command to check for projectile <-> player collisions. At times I've gone over cycle with just 4 pfread commands in one game loop.

 

Probably can mitigate this by checking only every other frame or more.

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The main issue I've had is using too much CPU time with the pfread command to check for projectile <-> player collisions. At times I've gone over cycle with just 4 pfread commands in one game loop.

 

Probably can mitigate this by checking only every other frame or more.

Agreed. I had the same problem with my 3d tennis game.

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It might be worth it to figure out a technique that determines which screen var the player is sitting on for a non 0 value. If it is greater than 0 do a pfread.

 

But, this is all theory and probably easier said than done :)

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