Blitter line mode examples?

LuigiThirty · 15 August 2017, 00:13

I have a 65816 program I wrote for the Apple IIgs that draws affine-transformed polygons and I'm trying to rewrite it for the Amiga in 68000 ASM. To avoid reinventing the wheel I want to use the blitter's line-drawing mode instead of writing a Bresenham algorithm for the millionth time. The examples in the hardware manual aren't easy to understand and I'm confused about all the options the line-drawing mode uses. Is there a simple "draw a line to one bitplane in any octant" example online somewhere I can start with?

idrougge · 15 August 2017, 01:33

The hardware reference manual has an example.

LuigiThirty · 15 August 2017, 07:49

So it does. I got it hooked up to my program and drawing 1px lines everywhere. and I'll see if I can deconstruct it and adapt it for my needs.

LuigiThirty · 16 August 2017, 20:53

Okay, I've got a weird problem where I can loop forever manually in the debugger but trying to run the rotation code in a loop locks up my system. I set up some debug output to SER: and the loop is only running once. Are my WaitVBL/WaitBlit macros correct or is there another problem I've overlooked? FrameLoop is the function that's looping and crashing.

https://pastebin.com/iVdHWKSj

LuigiThirty · 17 August 2017, 08:26

I fixed it - it was WaitBlit that was messed up.

And then after converting it to use the VBL interrupt I spent an hour figuring out why the interrupt wasn't being fired before realizing I had MuFastZero installed so modifying $6C didn't do anything anymore.

15 August 2017, 00:13	#1
LuigiThirty Registered User Join Date: Dec 2016 Location: USA Posts: 101	Blitter line mode examples? I have a 65816 program I wrote for the Apple IIgs that draws affine-transformed polygons and I'm trying to rewrite it for the Amiga in 68000 ASM. To avoid reinventing the wheel I want to use the blitter's line-drawing mode instead of writing a Bresenham algorithm for the millionth time. The examples in the hardware manual aren't easy to understand and I'm confused about all the options the line-drawing mode uses. Is there a simple "draw a line to one bitplane in any octant" example online somewhere I can start with?

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15 August 2017, 01:33	#2
idrougge Registered User Join Date: Sep 2007 Location: Stockholm Posts: 4,342	The hardware reference manual has an example.

15 August 2017, 07:49	#3
LuigiThirty Registered User Join Date: Dec 2016 Location: USA Posts: 101	So it does. I got it hooked up to my program and drawing 1px lines everywhere. and I'll see if I can deconstruct it and adapt it for my needs.

16 August 2017, 20:53	#4
LuigiThirty Registered User Join Date: Dec 2016 Location: USA Posts: 101	Okay, I've got a weird problem where I can loop forever manually in the debugger but trying to run the rotation code in a loop locks up my system. I set up some debug output to SER: and the loop is only running once. Are my WaitVBL/WaitBlit macros correct or is there another problem I've overlooked? FrameLoop is the function that's looping and crashing. https://pastebin.com/iVdHWKSj

17 August 2017, 08:26	#5
LuigiThirty Registered User Join Date: Dec 2016 Location: USA Posts: 101	I fixed it - it was WaitBlit that was messed up. And then after converting it to use the VBL interrupt I spent an hour figuring out why the interrupt wasn't being fired before realizing I had MuFastZero installed so modifying $6C didn't do anything anymore.

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