Basic Questions and Answers Thread

It is replacing unused Level 9.

 

I guess the music can be heard, looks like something isn't loading then.


It could be stopped at several points. I think you should first check the PLCs, then the level size data, and third the deformation routines. Make sure they all exist and are in the right format, the error is probably one of those.

 

Where are the deformation routines?

 

Under DeformBgLayer: there's an index (SwScrl_Index) which should send to "swscrl_minimal" for level 9. Since you didn't know, I assume you didn't modify it, so that one shouldn't be the problem.

 

I have a question. I'm trying to understand how the horizontal interrupt is working, and use it to load water palettes like s3 does.


So, in the "vectors", vector 29, is related to this. In s1, the content of the 29th vector is PalToCRAM, and in s3, it's $FFFFFFF6.


S1 sends directly to the right routine, while s3 stores "4EF9" in $FFFFFFF6 and the address of the routine to process in $FFFFFFF8 (a part of the program changes the content of those addresses). 4EF9 is "jmp" in hex. So, what's really in that vector (through the address) is, for example "jmp HInt4". So far, I think I'm not completely wrong yet. But, the question is...


When is it being processed? There should be an exception, but I can't find where/how it happens (ie how to tell the processor the right line has been reached).

 

The VDP has a register (8A) that deals with what number of lines should run until interruption is allowed, if we set it to 01, then every 1 line the interrupt will run, if we set it to 02, then every 2 lines the interrupt will run. The interrupt will run on the set lines when the beam is off and is moving back during what is known as a "Blanking Interval". Sonic games tend to set the line number based on the Y position of water, the problem here though is that if it's set to 03 (meaning 3 pixels from the top of the screen to display water), the next 3 lines after that the interrupt will run again, and the next 3 lines after that, etc. So they would presumably have a check to see if it's already been run once during the frame, and if so, skip the palette swapping (to make sure it only happens once).


That's the basic idea behind it anyway, no doubt different games (different Sonic games too probably) may go about programming it slightly differently, but the same method is there anyway.

 

Thanks.


The way I'd have done it, I'd have set the interruption line to the water level on screen, and on interruption, loaded the palette line, added 1 to the interruption line number, etc. But I can't find anything that simple in s3, so it looks like I'm still missing an important part of the program xD

 

Is it possible to edit the interrupts to make curved water? Like, a pool of water.


Or maybe the best way is to make a sprite to act as an "overlay" for the curved area and make that sprite animate in a way it looks transparent (and apply water physics too)


(read: various levels from project MD used this method)


What I mean is, lets say I want a level with water but only in one part of the level. First I would need to edit the water height object to also use X positions, but the main problem is the VDP stuff, can it allow specific pixels on the screen to palette switch, or maybe its only for lines/coloumns?


Theoretically, if I only move one pixel forward, only one pixel of water is supposed to show up, so all of the knewly drawn coloumn creates itself, while one specific pixel sets itself to palette switch. The main question is, how do you do it? Have other genesis/MD games done it before?

 

Maybe do it like the lava in mz. You have your blank tiles made up in soned2, and then include the art in sonic1.asm and then create the animation routine to load it etc. That way, whether you put those blank tiles in soned2, techinaly that should produce the desired sprite(s). Dunno if this would definatly work but think its one way of doing it.

 

Check the obj34_config subroutine. I noticed that the guide follows a 3-act configuration, but the game has originally 4. Try expanding this for 4 configs per zone.

 

Hi. How I can check into the object's code, what subtype is defined?


I don't know how to do these things the other objects, such as Obj2E, and Its not explained in the Work With Objects guide.


How I can do these checks?

 

$28(a-) is the space where the sub-type is loaded to.

 

Ok, and how to call a object with a subtype, with SingleObjLoad?

 

Load object, load object type in a0, load object subtype in $28(a0).

 

Ok, it worked perfecty ^^


I needed it, because my object table is complete (?)

 

I have a problem, when I compile my ROM, after making some edits to the code (I'm following a guide)


I see errors, but the compiler goes away before I can read them. Do you know what to type in the


command prompt to allow me to see the errors?

 

Pause


You write it at the bottom of your build.bat file and it will pause, forcing the window to stay opened.

 

I lol'd


add the "pause" command at the end of build.bat, and if you read some branch or out of range error, change the bsr by jsr, bra.X by jmp, or bne.b to bne.w... Something like this

 

So basically what I was trying is to do a health bar for my hack's bosses...

Code:

; ---------------------------------------------------------------------------

; Display routine

; ---------------------------------------------------------------------------



obj4f_Flash:

				lea	($FFFFD010).w,a4

				cmpi.w  #8,$21(a4)

				bne.s   s7_Hits

				bchg	#$0,$1C(a0)

				bra.s   Continue_Bar

s7_Hits:

				cmpi.w  #7,$21(a4)

				bne.s   s6_Hits

				bchg	#$1,$1C(a0)

				bra.s   Continue_Bar

s6_Hits:

				cmpi.b  #6,$21(a4)

				bne.s   s5_Hits

				bchg  #$2,$1C(a0)

				bra.s   Continue_Bar

s5_Hits:

				cmpi.b  #5,$21(a4)

				bne.s   s4_Hits

				bchg  #$3,$1C(a0)

				bra.s   Continue_Bar

s4_Hits:

				cmpi.b  #4,$21(a4)

				bne.s   s3_Hits

				bchg  #$4,$1C(a0)

				bra.s   Continue_Bar

s3_Hits:

				cmpi.b  #3,$21(a4)

				bne.s   s2_Hits

				bchg  #$5,$1C(a0)

				bra.s   Continue_Bar

s2_Hits:

				cmpi.b  #2,$21(a4)

				bne.s   s1_Hit

				bchg  #$6,$1C(a0)

				bra.s   Continue_Bar

s1_Hit:

				cmpi.b  #1,$21(a4)

				bne.s   Boss_Death_Remove

				bchg   #$7,$1C(a0)

				bra.s   Continue_Bar

Boss_Death_Remove:

				bchg  #$8,$1C(a0)

Continue_Bar:

		lea	(Ani_obj4f).l,a1		&#59; load animation script address

		jsr	AnimateSprite			&#59; load correct map ID based on the script

		jmp	DisplaySprite			&#59; save object ram space ready for display

But the frames aren't changing. What can I do? Thanks from advance

 

Hmm, try using a not odd RAM instead of a SST...