projectile patterns - NESdev BBS

projectile patterns
by psycopathicteen on 2016-08-04 (#176675)

I can't believe I haven't thought about this before, but projectile patterns can be programmed using data tables. The data tables can have information like, how many projectiles to throw at once, the x/y offset from the enemy, the speed and angle, the amount of time between projectile throws, and the looping information. This is probably old news to some people, but I've been so caught up with graphical trickery, that I haven't thought much about this.

Re: projectile patterns
by Myask on 2016-08-04 (#176683)

psycopathicteen wrote:

I can't believe I haven't thought about this before, but projectile patterns can be programmed using data tables. The data tables can have information like, how many projectiles to throw at once, the x/y offset from the enemy, the speed and angle, the amount of time between projectile throws, and the looping information. This is probably old news to some people, but I've been so caught up with graphical trickery, that I haven't thought much about this.

Angles should have option of being "absolute" or "relative to 'toward-player'".
Offsets should likewise be able to be able to be relative, as in "X pixels in direction-fired" with possible "Y pixels perpendicular to direction fired"
Projectile graphic/type
- And hitbox, if separate.

Re: projectile patterns
by psycopathicteen on 2016-08-09 (#177086)

Here is a code I just whipped up right now. It's for the 65816 though.

Code:

projectile_patterns:
ldy {projectile_data}
lda $0000,y
bpl +
sta {projectile_data}
tay
lda $0000,y
+;
inc {projectile_timer}
cmp {projectile_timer}
beq +
rts
+;
lda $0002,y
sta {temp}

iny #4

-;

jsr look_for_open_slot
cpx #{last_object_slot}
beq dont_spawn_projectile
lda $0000,y
sta.w {object_id},x

lda {direction}
sta.w {direction},x
bne +

lda {x_position}
clc
adc $00002,y
sta.w {x_position},x
bra ++
+;
lda {x_position}
sec
sbc $0002,y
sta.w {x_position},x
+;

lda {y_position}
clc
adc $0004,y
sta.w {y_position},x

lda $0006,y
sta.w {x_speed},x
lda $0008,y
sta.w {y_velocity},x

dont_spawn_projectile:

tya
clc
adc #$000a
tay

dec {temp}
bne -

sty {projectile_data}
stz {projectile_timer}
rts