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Parallax

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Here's a nice little graphical enhancement...

...and here's the video for it!
(I disabled collision detection for that video, so no silly comments, alright? [wink])

Now, there's a little problem with this system - well, a number of problems. The worst is this:

Oh dear. I'm now writing to the sprite table when the display is active, which (understandably) it does not like. On the Game Gear hardware, you can see this in the vertical bar of flickering stars towards the left hand side of the screen. I am not sure how I shall fix this, but I'm hoping that altering the sprite drawing routines to write to a RAM shadow then dumping the entire RAM shadow in the frame is faster than my current method which is to manually draw the sprites in a number of different routines.

The next problem is the detection of when to show/hide stars. Currently, it only does this based on tile index - so only tiles marked as being 0 are "transparent" and enable the stars (they're being drawn as sprites). This leads to them vanishing a good distance away from the edge of land.

Finally, there's the even weirder issue where the stars move at almost the same rate as the landscape but are shifted in alternate frames. If a star is on the boundary between tiles, one frame it is over tile 0 so is shown, next it is over tile X so is hidden, and this oscillates. Hopefully by fixing up a pixel-perfect "show/hide" function, I can fix up this problem as showing and hiding would be about 4 pixels away from the boundaries.

I have also started work on "Segue", a simple music system for Game Gear games. I'll support instruments (they just modulate the amplitude of notes when they are played) that can be bound to the different channels. The song itself will be a list of instructions - "play this tone X on channel Y" (where X is the period of the tone), "delay for X frames", "assign instrument X to channel Y" - that sort of thing.

EDIT: This journal is now low-res non-horizontal-scrolling friendly. [wink]
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looks great. hope you can solve the space and the vram problem :/

are you going to release the rom for firetrack online? that would be very nice. now that i think about it i dont think you can sell games for the gamegear anymore ;)

btw: i was trying to do your tunnel tutorial and i think everything worked but the getpixel form the texture surface (copied an example from the SDL page.)(red channel works, green channel looks like noise only and blue channel looks like (blue+noise)/2 ;) ) but i have a bunch of ideas for funky modifications so i will try to get it working...

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Thanks [smile]
Yes, I'll release the .gg ROM file for emulators (or dev carts) when finished. Good luck with the tunnel! As for the VRAM writes bug... *prepares to make next journal post*

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