silly little rotation effect

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psycopathicteen
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silly little rotation effect

Post by psycopathicteen » Sat Jul 24, 2010 4:33 pm

http://www.youtube.com/watch?v=SMrnxUF93HA

I was just playing around with graphics hardware.

tepples
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Post by tepples » Sat Jul 24, 2010 4:37 pm

Slow it down and it'd be a nice effect for a level on a ship.

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koitsu
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Post by koitsu » Sat Jul 24, 2010 5:01 pm

There's a SFC game which does exactly that -- it's called Septentrion (SOS in the US).

psycopathicteen
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Post by psycopathicteen » Sat Jul 24, 2010 5:17 pm

What level?

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koitsu
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Post by koitsu » Sat Jul 24, 2010 5:17 pm

The entire game.

EDIT: Here's an example (go to 04:45 or so).

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Post by ccovell » Sat Jul 24, 2010 5:38 pm

Teen's actually doing it a little differently from Septentrion. That game runs in Mode 7 all the time, and it's OK, because it doesn't need two background layers.

Teen's game needs parallax backgrounds which is impossible in Mode 7, so he uses one of the regular 2(?)-BG modes that allow for row & column raster effects. It's not rotation as much as X- and Y- shearing.

So a better comparison would be Gynoug/Wings of Wor on the MD.

Anyway, a cool-looking effect!

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Post by psycopathicteen » Sat Jul 24, 2010 6:24 pm

ccovell wrote:Teen's actually doing it a little differently from Septentrion. That game runs in Mode 7 all the time, and it's OK, because it doesn't need two background layers.

Teen's game needs parallax backgrounds which is impossible in Mode 7, so he uses one of the regular 2(?)-BG modes that allow for row & column raster effects. It's not rotation as much as X- and Y- shearing.

So a better comparison would be Gynoug/Wings of Wor on the MD.

Anyway, a cool-looking effect!
Great, now post your explanation on the website, http://www.atariage.com/forums/topic/16 ... i-do-this/

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Post by tepples » Sat Jul 24, 2010 7:17 pm

ccovell wrote:Teen's game needs parallax backgrounds which is impossible in Mode 7
Unless you fake them out of sprites, as seen in Cameltry/On the Ball. That can work unless you need more than half coverage in the background.
so he uses one of the regular 2(?)-BG modes that allow for row & column raster effects.
So it's the mode used for Tetris Attack and "Touch Fuzzy Get Dizzy" of Yoshi's Island, just with X shearing to match the Y offsets. I can sort of see the artifact here: fractional shear values update once every 8 values, just like on TFGD. Perhaps I'm just spoiled by the GBA, which has parallax mode 7 and four times the sprite overdraw but lacks offset per tile.
So a better comparison would be Gynoug/Wings of Wor on the MD.
I believe you're referring to this. Yes, it looks like the MD has offset per 16 pixels, but I'm not sure whether that and horizontal offset per tile/line can be used at once. But how the heck did Sonic 1 do its bonus stage?

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Post by tokumaru » Sat Jul 24, 2010 8:45 pm

tepples wrote:But how the heck did Sonic 1 do its bonus stage?
Sprites. Notice how the stages are designed without long straight sequences of blocks, to reduce the number of sprites sharing the same scanlines.

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Post by smkd » Sat Jul 24, 2010 9:38 pm

tepples wrote:Slow it down and it'd be a nice effect for a level on a ship.
Like Puggsy demonstrates. although the vertical 16 pixel columns are pretty noticable it still looks pretty good in motion. 8 pixel columns on the SNES would look much nicer.

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tokumaru
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Post by tokumaru » Sat Jul 24, 2010 10:24 pm

Is that how they made the Floating Island in Sonic & Knuckles too?

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Post by ccovell » Sun Jul 25, 2010 2:20 am

psycopathicteen wrote:Great, now post your explanation on the website, http://www.atariage.com/forums/topic/16 ... i-do-this/
Naah, I'll let other people try and figure it out.

By Wings of Wor, I was referring to the first level, yeah, but especially the 5th level: http://www.youtube.com/watch?v=R5OHr9H4yrU#t=0m50s

Gunstar Heroes does it for the helicopter too. Etc. (And, er, Vectorman just totally ripped off GH, didn't it?)

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Post by Dwedit » Sun Jul 25, 2010 3:13 am

I think it's really neat that you can accomplish simple affine transformations just by using Offsets Per Tile mode, combined with X scrolling. I never would have thought that this would work so well.

Looks like angles can range between -7.125 and 7.125 degrees before seeing artifacts from being too steep.
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Post by Bregalad » Sun Jul 25, 2010 5:28 am



I think it's really neat that you can accomplish simple affine transformations just by using Offsets Per Tile mode, combined with X scrolling. I never would have thought that this would work so well.
It works so well because cos(x) is close to 1 if x is close to 0, and because sin(x) is close to x if x is close to 0. (1st degree taylor devlopment).

I always had the feeling the "offset per tile" mode on the SNES went seriously under-used. Chrono Trigger's title screen, Contra III's first boss, and the elevators in Super Double Dragon's stage 1, it's all I can remember.
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Post by psycopathicteen » Sun Jul 25, 2010 6:45 am

I've always felt the same way too. Since it was commonly used on the Genesis but not on the Snes, and tile per offset mode was unknown to the gaming public, people started beleiving the 68000 was so fast that it could rotate large backgrounds pixel by pixel in real time.


It just goes to show you, Genesis got all the badass programmers, Snes got all the dorky programmers.

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