QBlit questions

carrion · 20 January 2017, 16:57

I'm quite new to the forum so.. Hi to All!
I try Blitz2 (2.1) for few days now and I get quite good IMO results with it. but I stumbled upon a issue that I don't think I understand well.

I have a background (on a 32col image) and I put a shape on it.
When I use Blit command it works OK, as suspected.
using the command:

Blit a,MouseX,MouseY
it works OK. meaning that it puts a shape on mouse pos.

but when I do Qblit 0,a,MouseX,MouseY It puts a black rect around the main shape. (aligned to 16 pixels).I think I use Unqueue right (after VWait)
And my understanding was that using QBlit will erase the shape itself bt it will preserve the background graphics.

Is it normal behaviour of QBlit?
Do I really have to do doublebuffering (meaning to repaint all background)?
If so then what's the use of QBlit then?

TIA

ps. oh and I tried to set the cookie mode explicitly.

idrougge · 20 January 2017, 17:02

Are your queues set up correctly?

carrion · 20 January 2017, 17:07

hm I have one queue #0 set like:
Queue 0,50

I mean my programming is very simple I draw the background and that's it.
then in the main loop i move the shape with the mouse.

idrougge · 20 January 2017, 17:43

Actually, that is the way Unqueue works.

You need to either restore the background from another bitmap using that bitmap number as the second argument to Unqueue, or use BBlit which buffers the background.

Shatterhand · 20 January 2017, 17:52

And then you also have to create a buffer instead of a Queue.

And then Unbuffer instead of Unqueue to delete the Bobs (and the background is restored)

Keep in mind this is considerably slower than doing a Unqueue / QBlit

carrion · 20 January 2017, 19:02

thank a lot guys it works with bblit and unbuffer but...

@shatterhand
ok. maybe it s slower but it works and I couldn't get it working with qblit and unquote? what did I do wrong?

I have a solution but I want to understand what i did wrong with Qblit and also the whole concept of Blit, Qblit, and BBlit.

idrougge · 21 January 2017, 01:25

You didn't do anything wrong with QBlit, that's simply how QBlit works.

Shatterhand · 21 January 2017, 01:40

Blit just put the shape on the bitmap.

QBlit puts the shape on the bitmap and adds it to a queue. When you empty the queue, all shapes are erased but BACKGROUND IS NOT RESTORED. You just erase everything.

BBlit puts the shape on the bitmap, but before it buffers the background it will overwrite to a buffer. When you empty the buffer, the shape is deleted and the background is restored.

QBlit is very useful when you know there's no background to restore. For example, I am working on a shoot'em up that uses Dual Playfield.. the background is at the back playfield and the main action happens at the front. I can use QBlit because there's no background to erase/restore , which is faster.

I also have another little prototype where enemies are always drawn where there's no background, so I can erase them safely, as I don't need to redraw everything after I erase the shapes

carrion · 21 January 2017, 14:28

thanks guys. appreciate the help.
please expect more questions from me, as I start to like blitz basic a lot

tolkien · 21 January 2017, 22:28

Perfect so I can learn from your questions too

20 January 2017, 16:57	#1
carrion Registered User Join Date: Dec 2016 Location: Warsaw area Posts: 152	QBlit questions I'm quite new to the forum so.. Hi to All! I try Blitz2 (2.1) for few days now and I get quite good IMO results with it. but I stumbled upon a issue that I don't think I understand well. I have a background (on a 32col image) and I put a shape on it. When I use Blit command it works OK, as suspected. using the command: Blit a,MouseX,MouseY it works OK. meaning that it puts a shape on mouse pos. but when I do Qblit 0,a,MouseX,MouseY It puts a black rect around the main shape. (aligned to 16 pixels).I think I use Unqueue right (after VWait) And my understanding was that using QBlit will erase the shape itself bt it will preserve the background graphics. Is it normal behaviour of QBlit? Do I really have to do doublebuffering (meaning to repaint all background)? If so then what's the use of QBlit then? TIA ps. oh and I tried to set the cookie mode explicitly.

20 January 2017, 17:02	#2
idrougge Registered User Join Date: Sep 2007 Location: Stockholm Posts: 4,338	Are your queues set up correctly? Last edited by idrougge; 20 January 2017 at 17:02. Reason: spell

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20 January 2017, 17:07	#3
carrion Registered User Join Date: Dec 2016 Location: Warsaw area Posts: 152	hm I have one queue #0 set like: Queue 0,50 I mean my programming is very simple I draw the background and that's it. then in the main loop i move the shape with the mouse.

20 January 2017, 17:43	#4
idrougge Registered User Join Date: Sep 2007 Location: Stockholm Posts: 4,338	Actually, that is the way Unqueue works. You need to either restore the background from another bitmap using that bitmap number as the second argument to Unqueue, or use BBlit which buffers the background.

20 January 2017, 17:52	#5
Shatterhand Warhasneverbeensomuchfun Join Date: Jun 2001 Location: Rio de Janeiro / Brazil Age: 41 Posts: 3,450	And then you also have to create a buffer instead of a Queue. And then Unbuffer instead of Unqueue to delete the Bobs (and the background is restored) Keep in mind this is considerably slower than doing a Unqueue / QBlit

20 January 2017, 19:02	#6
carrion Registered User Join Date: Dec 2016 Location: Warsaw area Posts: 152	thank a lot guys it works with bblit and unbuffer but... @shatterhand ok. maybe it s slower but it works and I couldn't get it working with qblit and unquote? what did I do wrong? I have a solution but I want to understand what i did wrong with Qblit and also the whole concept of Blit, Qblit, and BBlit.

21 January 2017, 01:25	#7
idrougge Registered User Join Date: Sep 2007 Location: Stockholm Posts: 4,338	You didn't do anything wrong with QBlit, that's simply how QBlit works.

21 January 2017, 01:40	#8
Shatterhand Warhasneverbeensomuchfun Join Date: Jun 2001 Location: Rio de Janeiro / Brazil Age: 41 Posts: 3,450	Blit just put the shape on the bitmap. QBlit puts the shape on the bitmap and adds it to a queue. When you empty the queue, all shapes are erased but BACKGROUND IS NOT RESTORED. You just erase everything. BBlit puts the shape on the bitmap, but before it buffers the background it will overwrite to a buffer. When you empty the buffer, the shape is deleted and the background is restored. QBlit is very useful when you know there's no background to restore. For example, I am working on a shoot'em up that uses Dual Playfield.. the background is at the back playfield and the main action happens at the front. I can use QBlit because there's no background to erase/restore , which is faster. I also have another little prototype where enemies are always drawn where there's no background, so I can erase them safely, as I don't need to redraw everything after I erase the shapes

21 January 2017, 14:28	#9
carrion Registered User Join Date: Dec 2016 Location: Warsaw area Posts: 152	thanks guys. appreciate the help. please expect more questions from me, as I start to like blitz basic a lot

21 January 2017, 22:28	#10
tolkien AmigaMan Join Date: Oct 2012 Location: Castro Urdiales/Spain Posts: 761	Perfect so I can learn from your questions too

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