How did Super Mario Bros. 3 create this tunnel vision effect?
In a certain section of World 8's map, the screen is black except for a small circle surrounding Mario (as seen below during this speedrun).
After doing a little research, I discovered that the game's cartridge contains a special mapper chip. This mapper, labeled MMC3, allows the generation of raster interrupts which are normally unavailable on the NES. In other words, the CPU can be interrupted, at most, once per scanline. Code may then be placed inside this interrupt to adjust certain PPU registers on a per-scanline basis, allowing for visual effects such as (presumably) the tunnel vision effect seen above.
What I don't understand, however, is how this specific effect was achieved (i.e., exactly what PPU registers the raster interrupts modified, if raster interrupts were even used at all).
nintendo nes
asked Dec 29 '18 at 21:14
cschultz2048
30325
add a comment |
In a certain section of World 8's map, the screen is black except for a small circle surrounding Mario (as seen below during this speedrun).
After doing a little research, I discovered that the game's cartridge contains a special mapper chip. This mapper, labeled MMC3, allows the generation of raster interrupts which are normally unavailable on the NES. In other words, the CPU can be interrupted, at most, once per scanline. Code may then be placed inside this interrupt to adjust certain PPU registers on a per-scanline basis, allowing for visual effects such as (presumably) the tunnel vision effect seen above.
What I don't understand, however, is how this specific effect was achieved (i.e., exactly what PPU registers the raster interrupts modified, if raster interrupts were even used at all).
nintendo nes
asked Dec 29 '18 at 21:14
cschultz2048
30325
1
I can't comment, but here's a link to the "source code" to Super Mario Bros. 3, with comments. github.com/captainsouthbird/smb3
– C. Uwakweh
2 days ago
add a comment |
In a certain section of World 8's map, the screen is black except for a small circle surrounding Mario (as seen below during this speedrun).
After doing a little research, I discovered that the game's cartridge contains a special mapper chip. This mapper, labeled MMC3, allows the generation of raster interrupts which are normally unavailable on the NES. In other words, the CPU can be interrupted, at most, once per scanline. Code may then be placed inside this interrupt to adjust certain PPU registers on a per-scanline basis, allowing for visual effects such as (presumably) the tunnel vision effect seen above.
What I don't understand, however, is how this specific effect was achieved (i.e., exactly what PPU registers the raster interrupts modified, if raster interrupts were even used at all).
nintendo nes
asked Dec 29 '18 at 21:14
cschultz2048
30325
In a certain section of World 8's map, the screen is black except for a small circle surrounding Mario (as seen below during this speedrun).
After doing a little research, I discovered that the game's cartridge contains a special mapper chip. This mapper, labeled MMC3, allows the generation of raster interrupts which are normally unavailable on the NES. In other words, the CPU can be interrupted, at most, once per scanline. Code may then be placed inside this interrupt to adjust certain PPU registers on a per-scanline basis, allowing for visual effects such as (presumably) the tunnel vision effect seen above.
What I don't understand, however, is how this specific effect was achieved (i.e., exactly what PPU registers the raster interrupts modified, if raster interrupts were even used at all).
nintendo nes
nintendo nes
asked Dec 29 '18 at 21:14
cschultz2048
30325
asked Dec 29 '18 at 21:14
cschultz2048
30325
asked Dec 29 '18 at 21:14
cschultz2048
30325
asked Dec 29 '18 at 21:14
cschultz2048
30325
asked Dec 29 '18 at 21:14
cschultz2048
30325
30325
1
I can't comment, but here's a link to the "source code" to Super Mario Bros. 3, with comments. github.com/captainsouthbird/smb3
– C. Uwakweh
2 days ago
add a comment |
1
I can't comment, but here's a link to the "source code" to Super Mario Bros. 3, with comments. github.com/captainsouthbird/smb3
– C. Uwakweh
2 days ago
1
1
I can't comment, but here's a link to the "source code" to Super Mario Bros. 3, with comments. github.com/captainsouthbird/smb3
– C. Uwakweh
2 days ago
I can't comment, but here's a link to the "source code" to Super Mario Bros. 3, with comments. github.com/captainsouthbird/smb3
– C. Uwakweh
2 days ago
add a comment |
1 Answer
1
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votes
No MMC3 tricks are used for this effect; just standard background and sprite manipulation. Tiles that are completely invisible are replaced with a blank tile, while black sprites forming a circle outline cover the partially-visible tiles.
We can make the effect more obvious by drawing background and sprites separately (and coloring the circle sprites white instead of black):
answered Dec 29 '18 at 22:08
NobodyNada
3,1511428
6
+1 excellent GIF. I was beginning to suspect that this was the case, but I appreciate you confirming my suspicions.
– cschultz2048
Dec 29 '18 at 22:39
+1. Sometimes the answer is much simpler than people imagine. Thanks for reminding us of that.
– cbmeeks
7 hours ago
add a comment |
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1 Answer
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1 Answer
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active
oldest
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active
oldest
votes
active
oldest
votes
No MMC3 tricks are used for this effect; just standard background and sprite manipulation. Tiles that are completely invisible are replaced with a blank tile, while black sprites forming a circle outline cover the partially-visible tiles.
We can make the effect more obvious by drawing background and sprites separately (and coloring the circle sprites white instead of black):
answered Dec 29 '18 at 22:08
NobodyNada
3,1511428
6
+1 excellent GIF. I was beginning to suspect that this was the case, but I appreciate you confirming my suspicions.
– cschultz2048
Dec 29 '18 at 22:39
+1. Sometimes the answer is much simpler than people imagine. Thanks for reminding us of that.
– cbmeeks
7 hours ago
add a comment |
No MMC3 tricks are used for this effect; just standard background and sprite manipulation. Tiles that are completely invisible are replaced with a blank tile, while black sprites forming a circle outline cover the partially-visible tiles.
We can make the effect more obvious by drawing background and sprites separately (and coloring the circle sprites white instead of black):
answered Dec 29 '18 at 22:08
NobodyNada
3,1511428
6
+1 excellent GIF. I was beginning to suspect that this was the case, but I appreciate you confirming my suspicions.
– cschultz2048
Dec 29 '18 at 22:39
+1. Sometimes the answer is much simpler than people imagine. Thanks for reminding us of that.
– cbmeeks
7 hours ago
add a comment |
No MMC3 tricks are used for this effect; just standard background and sprite manipulation. Tiles that are completely invisible are replaced with a blank tile, while black sprites forming a circle outline cover the partially-visible tiles.
We can make the effect more obvious by drawing background and sprites separately (and coloring the circle sprites white instead of black):
answered Dec 29 '18 at 22:08
NobodyNada
3,1511428
No MMC3 tricks are used for this effect; just standard background and sprite manipulation. Tiles that are completely invisible are replaced with a blank tile, while black sprites forming a circle outline cover the partially-visible tiles.
We can make the effect more obvious by drawing background and sprites separately (and coloring the circle sprites white instead of black):
answered Dec 29 '18 at 22:08
NobodyNada
3,1511428
answered Dec 29 '18 at 22:08
NobodyNada
3,1511428
answered Dec 29 '18 at 22:08
NobodyNada
3,1511428
answered Dec 29 '18 at 22:08
NobodyNada
3,1511428
3,1511428
6
+1 excellent GIF. I was beginning to suspect that this was the case, but I appreciate you confirming my suspicions.
– cschultz2048
Dec 29 '18 at 22:39
+1. Sometimes the answer is much simpler than people imagine. Thanks for reminding us of that.
– cbmeeks
7 hours ago
add a comment |
6
+1 excellent GIF. I was beginning to suspect that this was the case, but I appreciate you confirming my suspicions.
– cschultz2048
Dec 29 '18 at 22:39
+1. Sometimes the answer is much simpler than people imagine. Thanks for reminding us of that.
– cbmeeks
7 hours ago
6
6
+1 excellent GIF. I was beginning to suspect that this was the case, but I appreciate you confirming my suspicions.
– cschultz2048
Dec 29 '18 at 22:39
+1 excellent GIF. I was beginning to suspect that this was the case, but I appreciate you confirming my suspicions.
– cschultz2048
Dec 29 '18 at 22:39
+1. Sometimes the answer is much simpler than people imagine. Thanks for reminding us of that.
– cbmeeks
7 hours ago
+1. Sometimes the answer is much simpler than people imagine. Thanks for reminding us of that.
– cbmeeks
7 hours ago
add a comment |
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1
I can't comment, but here's a link to the "source code" to Super Mario Bros. 3, with comments. github.com/captainsouthbird/smb3
– C. Uwakweh
2 days ago