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Mandelbrot Set

This SystemVerilog demo uses fixed-point multiplication and a small framebuffer to render the Mandelbrot set.

This design has an associated Project F blog post: Mandelbrot in Verilog.

I've included project files for:

This demo makes use of modules from the Project F library.

Mandelbrot set rendered by Verilator/SDL.

Demo Parameters

We consider up to 255 iterations by default, but you can adjust this by changing ITER_MAX in the top module. The minimum number of iterations supported is 128, but you get the best results with 2n-1, for example, 511, as this best uses the full range of colours.

With the default 25-bit precision, you can zoom in 15 times to a minimum step of 1/221. You can adjust the precision by changing FP_WIDTH in the top module (don't forget to adjust X_START, Y_START, and STEP).

Xilinx 7-Series FPGAs

This demo have been tested with:

  • Vivado 2022.2

Arty A7-35T Build

To create a Vivado project for the Digilent Arty A7-35T with Pmod VGA; clone the projf-explore git repo, then start Vivado and run the following in the Tcl console:

cd projf-explore/demos/mandelbrot/xc7-vga/arty-a7-35
source ./create_project.tcl

You can then build top_mandel as you would for any Vivado project.

Button controls:

  • BTN2 - left/up/zoom-out
  • BTN1 - select mode: horizontal/vertical/zoom
  • BTN0 - right/down/zoom-in
  • RESET - return to starting coordinates and zoom

NB. Controls don't work if rendering is in progress.

Four green LEDs show status:

  • LD7 - rendering in progress
  • LD6 - horizontal motion
  • LD5 - vertical motion
  • LD4 - zoom

Nexys Video DVI Build

To create a Vivado project for the Digilent Nexys Video with DVI output; clone the projf-explore git repo, then start Vivado and run the following in the Tcl console:

cd projf-explore/demos/mandelbrot/xc7-dvi/nexys-video
source ./create_project.tcl

You can then build top_mandel as you would for any Vivado project.

Button controls:

  • BTNU - left/up/zoom-out
  • BTNC - select mode: horizontal/vertical/zoom
  • BTND - right/down/zoom-in
  • CPU_RESET - return to starting coordinates and zoom

NB. Controls don't work if rendering is in progress.

Four green LEDs show status:

  • LD3 - rendering in progress
  • LD2 - horizontal motion
  • LD1 - vertical motion
  • LD0 - zoom

Verilator

This demo have been tested with:

  • Verilator 4.038 (Ubuntu 22.04 amd64)
  • Verilator 5.006 (macOS 13 arm64)

Verilator Build

If this is the first time you've used Verilator and SDL, you need to install dependencies.

Build the demo:

cd projf-explore/demos/mandelbrot/verilator-sdl
make

Run the simulation executable from obj_dir:

./obj_dir/mandelbrot

Keyboard controls:

  • Up Arrow - left/up/zoom-out
  • Space Bar - select mode: horizontal/vertical/zoom
  • Down Arrow - right/down/zoom-in

NB. Controls don't work if rendering is in progress.

You can quit the simulation by pressing the Q key.

To run in fullscreen mode, edit main_mandelbrot.cpp so that FULLSCREEN = true, then rebuild.