[object List Refresh Method] Opinion

[Matmook]

Hi,

 

Rebuilding my GPU code from scratch because I now need to have a double object list... and have a clean code too (test + test + test == unreadable code ).

Here is the object list refresh mechanism I'm going to do... Don't know if this is a good method so your opinion are welcome

 

Here is the context :

 

Each "sprite" is defined in a structured array (Pseudo-Strange code) :

Struct {

Phrase1; // 1st bitmap phrase (YPOS, DATA,LINK...)

Phrase2; // 2nd phrase (XPOS, FLAGS ,...)

Phrase3; // scaled bitmap phrase

PosX;

PosY;

Layer;

Mode;

...

} Sprite;

 

Each Sprite include space for a copy of the whole object (4 LONG for bitmap object and 6 for scaled object).

 

I used 2 different Object List (one currently displayed and one for modifications) :

- Branch OBJECT (before display start-> Stop)

- Branch OBJECT (after display end -> Stop)

- Bitmap

- Bitmap

- ... many bitmap...

- Stop

 

I use 2 pointer for those Object List :

@currentlist

@worklist

 

The OLP always use @currentlist for the display.

 

 

* The GPU is set to build the new list on each VBL (via the 68k interrupt) :

Use @worklist

Jump over the 2 legacy branch objet (@worklist = @worklist + 4 LONG)

For i in 0 to numsprite

{

load saved phrase from sprite struct (we must (at least) correct the LINK).

compute next link (ie +4 or +6 depending of the type)

change X, Y, zoom, ...

save phrase to @worklist

@worklist = @worklist + 4 LONG (or 6)

}

add stop object

swap @worklist / @currentlist

Set OLP use this new @worklist

stop GPU.

 

Is this a good method or not ?

 

 

 

[Zerosquare]

Look OK to me. There are probably ways to optimize this (only updating what's necessary instead of using "brute force"), but I wouldn't bother if your code runs in 1 VBL with the current method.

 

Don't forget that sprite objects must be aligned on a 16-byte boundary, and scaled sprite objects on a 32-byte boundary. So you can't just add 4 or 6 to compute the address of the following object in the list, you have to round up too.

[Matmook]

Look OK to me. There are probably ways to optimize this (only updating what's necessary instead of using "brute force"), but I wouldn't bother if your code runs in 1 VBL with the current method.

The idea is to let the GPU make the new list using the "sprite struct list" (animation ...) in this case I need to copy "unchanged part" of the object .

In the other hand, job not done on gpu must be done using the 68k and the GPU is faster than the 68k so

 

I hope this method (x128 sprite for example) do not take too much GPU time ... I "just" want to manage my sprite list (adding, remove, "Z ording" ...) using the 68k.

 

I don't know ... let's try it ...

 

Don't forget that sprite objects must be aligned on a 16-byte boundary, and scaled sprite objects on a 32-byte boundary. So you can't just add 4 or 6 to compute the address of the following object in the list, you have to round up too.

 

I've not test scaled bitmap for the moment but this is a really important information ... I must make space for those object or place them in another room to loose less memory (since there should be less scaled bitmap than normal one in a game...)

 

Thanks

 

 

[Matmook]

The idea is to let the GPU make the new list using the "sprite struct list" (animation ...) in this case I need to copy "unchanged part" of the object .

In the other hand, job not done on gpu must be done using the 68k and the GPU is faster than the 68k so

 

I hope this method (x128 sprite for example) do not take too much GPU time ... I "just" want to manage my sprite list (adding, remove, "Z ording" ...) using the 68k.

 

I don't know ... let's try it ...

 

 

 

I've not test scaled bitmap for the moment but this is a really important information ... I must make space for those object or place them in another room to loose less memory (since there should be less scaled bitmap than normal one in a game...)

 

Thanks

 

 

It runs ... I can now add/remove sprite easily.

I need to learn how to use scaled bitmap... Let's go !

[Cyrano Jones]

The way we do it in ProjectOne is:

 

Create a "shadow object list" with all objects 32 bytes apart regardless of what they are - this assures an object is always phrase aligned. The links in the shadow are computer for where the live list is.

 

Store the creation address of each object all in a table.

 

During the VBL, use the blitter to copy the shadow to the live.

 

During the game you can then work on the shadow patching x/y/bitmap addresses. If you dont want something, modify a branch to skip it (eg, change the branch before a long string of objects from always to never) or just move its x/y to offscreen (if you have enough objectlist time to do this)

 

If you are doing object culling (Y-sorting) - we do this for the bullets - then you can loop around the shadow list changing just the link addresses.

 

I can mail you the code if you like?

[Matmook]

Here is the method I currently use :

 

- My sprite list is defined in an array (X, Y, bitmap, animation ptr, transparency,.... and also a copy of the corresponding OLP object phrase)

- One active object list

- One secondary object list

 

For the moment I manage to modify my sprite list using 68k but I hope to swap GPU code for that in the future.

 

On VBL I do the following things :

- play music (SebRMV's player)

- set a flag in G_RAM to inform the GPU that the VBL is here (I think I can use GPU interrupt for this in the future).

 

On GPU I do the following things :

- clear my vblflag

- swap active and secondary object list (I display the last computed one)

- compute the next object list using my sprite list information (simply restore object's phrase if nothing has changed or compute the new object if change happened ... like animation ....)

- wait for the vblflag (in local ram) to be set again and loop

 

I don't know if it is the good method but it runs so I'm going to improve this one.

 

Next I need to create a chained list in my sprite list to simplify sprite deletion/replacement/move and build a tool to create all animation (done by hand for the moment).

[Cyrano Jones]

If it works, it works! :-)