SpritesMind.Net

Hello,

I want to use Horizontal scrolling per tile mode, and I see I shuld use :
I read that TransferMethod tm can be :
What is the difference between DMA_QUEUE and DMA_QUEUE_COPY ?

I also was wondering something : I want to simulate parallax scrolling in one plane : lines above line 448 of the map must scroll at half-speed, lines below at full speed.

There can be vertical scroll, so line 448 of the map is not always at the same screen height (let's call scanline the corresponding screen line).

So tile hscroll isn't enough, I must enable line hscroll...

Wouldn't it be faster keep plane hscroll mode, to activate HInt at (scanline - 1), then change the HScroll register in HInt ?

Looks like you're using last repository version, be careful it's still a bit experimental but it should work :p
I tried to document the DMA_QUEUE_COPY from the doxygen but i admit it remains obscure:

Copy the buffer and put in the DMA queue so it will be transferred at next VBlank

The difference between DMA_QUEUE and DMA_QUEUE_COPY is that the latter will copy the data you want to transfer though DMA in a temporary buffer first (doing a CPU copy for that) and this temporary buffer will be used as source when DMA will actually occurs. This is important when your source buffer may be modified before DMA actually occurs so in the end wrong data may be transferred. Of course it wastes lot of CPU time doing the software copy but what matter is to optimize VBlank usage so it's still interesting in the end.

tryphon wrote: Tue Apr 14, 2020 8:59 am Wouldn't it be faster keep plane hscroll mode, to activate HInt at (scanline - 1), then change the HScroll register in HInt ?

Using line scroll just for a single parallax is really a waste of performance (as you need to update scroll value for each line). Of course it's *much* better to use Hint here (single hint is enough) to change global hscroll when needed

Thanks, you confirm what I thought

So, is this the way to do it :

1) just after VBlank, I set register 10 with the (scanline - 1) and enable HInt (with a custom callback function) :
2) the callback function sets the HScroll value and disable HInt ?
(I'm not totally sure about how SYS_setInterruptMaskLevel works, nor the order of doing things )

Am I sure not to break something when disabling HInt ? (asked differently : does SGDK use HInt in "normal" use ?)

Well, that was almost that
No need to deal with the SYS_setInterruptMaskLevel(...) stuff, it should be fine by default.

Then in your callback :
Use the plan scroll set function, not the tile scroll here. And again you don't need to care about the interrupt level stuff, SGDK handle that for you. it's safer to not touch it

Thanks

But don't I need to disable HInt at the end of my_callback() ?

If I don't do it, won't HInt be triggered at every line after scanline ?

Oh yeah you're right, it will be called at each "scanline - 1" so if "scanline -1" is lower than 112 (2x112=224 lines) then indeed you will have multiple calls for a single screen. I think the easiest solution is indeed to call VDP_setHInterrupt(FALSE) after the scrolling change. Then don't forget to re-enabled it after waitVSync() (or into your vint callback if you have one).

Thank you, it seems to work like a charm

Get ready Black Turtle !

Well done !

Black Turtle ? :p

(image attachment doesn't seem to work : it's the second boss of Shinobi arcade )

Oh i never realized that was the name of second boss :p