Amiga 500 demo featuring the following technical highlights:
- Assembly programming on the Motorola 68000 for calculating 3D-rotation of the globe.
- Color cycling for both the ocean and the text performed during by the vertical blank by the Copper.
- Text reflection waves are obtained by sine cycling during the horizontal offset. This is done by a dynamic Copper list.
- Efficient use of bitplanes:
- The globe rotation is only done on the fifth bitplane in order to achieve the required speed-up. Hence, the color gradients of the continents are obtained by a static Copper list that sets the colors registers 16 to 31 to the same value.
- Night on earth is obtained "for free" by extra half-bright mode - the sixth bitplane is set on the left third for nighttime.
- As the 68000 is still to slow to calculate 3d-animations of this size, about half of the animation is pre-calculated initially and stored in chip memory. During animation, the 68000 and the Blitter operate in parallel. For each frame, the former calculates the remaining portion of the animation and the Blitter copies the precalculation into the frame.
- This precalculation lasts about two minutes. So you need to be patient at the start.
- Background music (my original score).
The easiest way is to put the repository into a mounted directory of an emulated A500 and to invoke the executable which is provided for convenience.
cd bin
Demo
At the start, the precalculation of the animation lasts about two minutes. So you need to be patient.
The sources are also included. Within your assembly IDE, you need to assemble src/Demo and start it from the src folder (relative pathes at work...).
I used this demo as an intro for a self-made computer game. Just in case you wonder about that strategic simulations stuff. Also, the bottom text morphed constantly to provide information about the game. This is also removed from this repo.
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| Early version of two colors only but featuring the full globe animation |
