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RoboticRocketeer

Wondering Why Id Monsters Double Each Walk Frame

Question

While exploring the DECORATE definitions for monsters, I noticed each walk frame occurs twice consecutively, in nearly every monster. For DoomImp:

 

Quote

TROO AABBCCDD 3

 

My first reaction was to wonder why not use something cleaner like:

Quote

TROO ABCD 6

 

Then I theorized that Id did this to split each frame into two half-length segments, to allow a monster to change direction more rapidly... so it won't be as locked into a particular course.

 

Is that true, or am I ignorant?

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In the original game, monster movement wasn't interpolated. Traveling more often, but at less distance = less jerky. Also better maneuverability in tight spaces.

 

If they had twice as many sprites for walking, they'd make it so that each movement is accompanied by a change of sprite, but that would require more work and more memory to store the graphics.

 

Monster aggression also depends on how often you call the movement codepointer. I'd say it's all tied together, but the smooth movement was probably the main reason.

 

Edited by Da Werecat

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2 hours ago, bzzrak said:

Just a little (DEH) question, if I combine all of the "split" frames, will I get any side effects? Sounds like a good way of getting a few extra states.

If all frames in the animation loop have the same duration and call the same function (which is not the case with monsters like Arachnotron / Cyberdemon / Mastermind, who call a different function on certain frames to play stomping sounds), then you can combine the frames while keeping the duration the same (so for example, "AABBCCDD 3" will be changed into "ABCD 3", and NOT "ABCD 6"), and the resulting change will be purely cosmetic (faster animation, seemingly jankier movement), whereas all gameplay-related characteristics of the monster will remain the same (movement speed, aggressivity, exact walking pattern, RNG-dependent actions, everything).

 

You could even change the loop "AABBCCDD 3" into just "A 3", or "YXOIKBNSDHFUQN 3", and there would still be no gameplay change, only appearance change.

Edited by scifista42

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Probably also a remnant from a time when Doom was meant to run at 70 fps #inb4Blastfrog

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16 minutes ago, Da Werecat said:

In the original game, monster movement wasn't interpolated. Traveling more often, but at less distance = less jerky. Also better maneuverability in tight spaces.

 

...

 

Monster aggression also depends on how often you call the movement codepointer. I'd say it's all tied together, but the smooth movement was probably the main reason.

 

Thanks. This answer also let me infer what interpolation means in reference to monster sprites, too. Now it all makes sense.

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Just a little (DEH) question, if I combine all of the "split" frames, will I get any side effects? Sounds like a good way of getting a few extra states.

 

edit: scifista42 is the best, thanks pal.

Edited by bzzrak

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Coffee or excitement for human blood.

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