#+TITLE: Sixth 3D engine demos

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* General
- This is a subproject of [[http://www3.svjatoslav.eu/projects/sixth-3d/][Sixth 3D]] which in turn is a subproject of
  [[http://www3.svjatoslav.eu/projects/sixth/][Sixth]].

- This program is free software: you can redistribute it and/or modify
  it under the terms of the [[https://www.gnu.org/licenses/lgpl.html][GNU Lesser General Public License]] as
  published by the Free Software Foundation, either version 3 of the
  License, or (at your option) any later version.

- Program author:
  - Svjatoslav Agejenko
  - Homepage: http://svjatoslav.eu
  - Email: mailto://svjatoslav@svjatoslav.eu

- [[http://www.svjatoslav.eu/projects/][Other software projects hosted at svjatoslav.eu]]

** Source code
- [[http://www2.svjatoslav.eu/gitweb/?p=sixth-3d-demos.git;a=snapshot;h=HEAD;sf=tgz][Download latest snapshot in TAR GZ format]]

- [[http://www2.svjatoslav.eu/gitweb/?p=sixth-3d-demos.git;a=summary][Browse Git repository online]]

- Clone Git repository using command:
  : git clone http://www2.svjatoslav.eu/git/sixth-3d-demos.git

* Overview
Goal of this project is to show off capabilities and API usage of
[[http://www3.svjatoslav.eu/projects/sixth-3d/][Sixth 3D]] engine.

All sample scenes below are rendered at interactive framerates.
* Navigating in space
| key                            | result                               |
|--------------------------------+--------------------------------------|
| cursor keys                    | move: left, right, forward, backward |
| mouse scroll wheel             | move: up, down                       |
| dragging with mouse            | look around                          |

* Samples
** Raytracing through voxels
[[file:screenshots/raytracing fractal in voxel polygon hybrid scene.png]]

Test scene that is generated simultaneously using:
+ conventional polygons
  + for realtime navigation, and
+ voxels
  + for on-demand raytracing

Instead of storing voxels in dumb [X * Y * Z] array, dynamically
partitioned [[https://en.wikipedia.org/wiki/Octree][octree]] is used to compress data. Press "r" key anywhere in
the scene to raytrace current view through compressed voxel
datastructure.

** Conway's Game of Life
The Game of Life, also known simply as Life, is a cellular automaton
devised by the British mathematician John Horton Conway in 1970.

+ https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life
  + Game rules:
    + 2 cell states: alive / dead
    + Each cell sees 8 neighboring cells.
    + If alive cell neighbors count is 2 or 3, then cell survives,
      otherwise it dies.
    + Dead cell becomes alive if neighbors count is exactly 3.

[[file:screenshots/life.png]]

Current application projects 2D game grid/matrix onto three
dimensional space. Extra dimension (height) is used to visualize
history (previous iterations) using glowing dots suspended in space.

Usage:
| key                            | result                               |
|--------------------------------+--------------------------------------|
| mouse click on the cell (cell) | toggles cell state                   |
| <space>                        | next iteration                       |
| ENTER                          | next iteeration with the history     |
| "c"                            | clear the matrix                     |

** Text editors
[[file:screenshots/text editors.png]]

Initial test for creating user interfaces in 3D and:
+ window focus handling
+ picking objecs using mouse
+ redirecting keyboard input to focused window


Window focus acts like a stack.

When window is clicked with the mouse, previously focused window (if
any) is pushed to the focus stack and new window receives focus. Red
frame appears around the window to indicate this.

When ESC key is pressed, window focus is returned to previous window
(if any).

When any window is focused, all keyboard input is redirected to that
window, including cursor keys. To be able to navigate around the world
again, window must be unfocused first using ESC key.


+ TODO:
  + Improve focus handling:
    + Perhaps add shortcut to navigate world without exiting entire
      stack of focus.
    + Possibility to retain and reuse recently focused elements.
    + Store user location in the world and view direction with the
      focused window. So that when returning focus to far away object,
      user is redirected also to proper location in the world.
  + Possibility to store recently visited locations in the world and
    return to them.
** Mathematical formulas
[[file:screenshots/mathematical formulas.png]]

+ TODO: instead of projecting 2D visualizations onto 3D space,
  visualize some formula using all 3 dimensions avaliable.
** Sinus heightmaps and sphere
[[file:screenshots/sinus heightmaps and sphere.png]]

Simple test scene. Easy to implement and looks nice.