648 Warp
648 : Warp
- Author: sylefeb
- Description: Demo on TinyTapeout? Let's do something!
- GitHub repository
- Clock: 25000000 Hz
Warp
Please make sure to watch the demo for a few minutes as various effects play out before it loops. At start it waits for a few seconds to ensure VGA sync is achieved.
How it works
Preface
This demo is written in Silice, my HDL. Here is the actual source. Silice now fully support TinyTapeout as a build target.
Graphics
The core effect is a classical tunnel effect ; however this is normally done with a "huge" pre-computed table having one entry per-pixel. So I thought it'd be challenging and fun to do it while racing the beam! Plus, I really like this effect.
There are several tricks at play: a shallow CORDIC pipeline to compute an atan and length, and a few precomputed 1/x distances to interpolate between -- these form keypoint rings along the tunnel. All the effects are then obtained by combining multiple layers in various ways (like a tunnel effect processor which registers can be configured for various effects).
The demos uses a lot of dithering (ordered Bayer dithering) given the output is RGB 2-2-2. All computations are grayscale and the RGB lense effect is obtained by delaying the grayscale values using the tunnel distance in R and B.
I also tried to make the logo interesting by deviating from a classical pixelated look. It is composed of tiles, either full or triangular, with a comparator and a bit of logic to do all four possible triangles.
The tunnel viewpoint change is obtained simply by shifting the tunnel center. I was surprised that a simple translation gives such a convincing effect (almost as if the viewpoint was rotating).
The 'blue-orange' tunnel effect is obtained through temporal dithering, one frame being the standard tunnel, the other the rotated tunnel. This gets combined with the RGB lense distortion, achieving the final look.
Audio
I am no musician, so making a soundtrack was a challenge for me, but that's something I've always wanted to try. In the end it was a very enjoyable part of the design, and I was surprised at how compact this can be made, the soundtrack using perhaps around 10% of the entire design.
I tried to make a track that matches the spirit and rhythm of the graphics. It is what is is, but I'm happy that there's sound at all!
How to test
Plug the VGA+audio PMODs to the board and run. Maybe it works?
Simulation of both audio and video can run on an ECPIX5, with the Diligent VGA PMOD on ports 0,1 and an I2S audio PMOD on port 2 (upper row). The audio also runs on an ULX3S using its DAC (but no video in this case).
External hardware
- VGA PMOD
- Audio PMOD
See https://tinytapeout.com/competitions/demoscene/
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | R1 | ||
| 1 | G1 | ||
| 2 | B1 | ||
| 3 | VS | ||
| 4 | R0 | ||
| 5 | G0 | ||
| 6 | B0 | ||
| 7 | HS | Audio |