7-bits
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Long VBlank
Long VBlank is a demo for the 8-bit Atari XL/XE. It was shown on 14 November 2026 at Silly Venture 2026 Winter Edition in Gdańsk, Poland, in the Atari XL/XE Demo Standard competition.
Long VBlank
Effects
- Wireframe 3D
- Flat and Gouraud shading
- Texture mapping
- A corridor in the style of Wolfenstein 3D
- A voxel landscape in the style of Comanche
How It Works
A PAL frame lasts 35,568 CPU cycles, and the video chip takes about 3,840 of them, so every effect was measured in cycles per frame. All maths uses signed bytes and table-based multiplication. The wireframe cube runs at 16.3 frames per second, the Gouraud-shaded one at 7.0.
The project has its own tools, written in Python: a 6502 assembler and a cycle-counting emulator with a model of the PAL frame; automated tests use them to check the renderer and the whole timeline frame by frame.
Requirements
An Atari 800XL, 65XE or 130XE with 64 KB, PAL, no extensions. The XEX file loads directly in an emulator, from SIO2SD, SIO2PC or a flash cartridge, or from Atari DOS 2.5; other DOS versions may not work. The ATR file is a bootable disk image.
Download
The demo is freeware.
- longvbl.xex (34 KB)
- longvbl.atr (90 KB)
- long-vblank.zip (35 KB): both files and the release notes