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Strepto
Registered: Dec 2015
Posts: 11 |
Kefrens bars
I've been thinking about kefrens bars on the c64.
How do you think it is implemented?
Perhaps using repeated char lines and update the chars using cycle exact timing? |
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Smasher
Registered: Feb 2003
Posts: 520 |
hey, I'm not a fan of Kefrens bars, but cool to have you back in bizz Strepto! :) |
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HCL
Registered: Feb 2003
Posts: 728 |
@Krill: :) |
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Oswald
Registered: Apr 2002
Posts: 5094 |
repeating last row is now not stretching but linecrunch ?! or that is the same timing that results in bitmap move up ? |
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Golara
Account closed
Registered: Jan 2018
Posts: 212 |
Quote: repeating last row is now not stretching but linecrunch ?! or that is the same timing that results in bitmap move up ?
Linecrunch is what is used for moving the bitmap up, but what really happens is that the last pixel line of a char is displayed only, so you skip the 7 pixel lines, because of that, the next char line is drawn higher than normal, repeat that and you scroll bitmap up. Here the same technique is used but instead of moving bitmap data, the whole screen is just these pixel lines from 7th line of a char and that line is modified to look like kefrens. |
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Oswald
Registered: Apr 2002
Posts: 5094 |
yes I get all that, I was asking why is Krill calling a stretcher linecrunch, probably same routine with different result in different gfxmode. I havent coded linecrunch, but have done kefrens. |
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Krill
Registered: Apr 2002
Posts: 2980 |
Quoting OswaldI was asking why is Krill calling a stretcher linecrunch Mostly because the term "stretcher" is rather ambiguous, as it could be repeated badlines, repeated char rows (without badlines), linecrunching, or something i just forgot. |
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Oswald
Registered: Apr 2002
Posts: 5094 |
linecrunch as I understood it, reduces whole char rows to a single rasterline, what is being stretched ? |
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Krill
Registered: Apr 2002
Posts: 2980 |
Quoting Oswaldlinecrunch as I understood it, reduces whole char rows to a single rasterline, what is being stretched ? The same rasterline will be repeated, as there is no DMA (badline) to fetch new char data, and RC will remain at 7. Thus, there is stretching. |
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Oswald
Registered: Apr 2002
Posts: 5094 |
linecrunch crunches lines (char rows) down to a single rasterline, and this is used to move the screen upwards, so there should be badlines and not the same single rasterline displayed but in each rasterline a new char row in 1 pixel high glory ? |
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Krill
Registered: Apr 2002
Posts: 2980 |
Quoting Oswaldlinecrunch crunches lines (char rows) down to a single rasterline, and this is used to move the screen upwards, so there should be badlines and not the same single rasterline displayed but in each rasterline a new char row in 1 pixel high glory ? If you linecrunch continuously, with a write to $d011 each rasterline, there will be no badlines. Once you stop writing to $d011, the last rasterline of the current char row will be repeated, but after that, there will be normal badline DMA action and new lines as normal, with whatever line counter is left after all the linecrunching. |
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