#+TITLE: Sixth 3D - 3D engine

* (document settings) :noexport:
** use dark style for TWBS-HTML exporter
#+HTML_HEAD: <link href="https://bootswatch.com/3/darkly/bootstrap.min.css" rel="stylesheet">
#+HTML_HEAD: <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
#+HTML_HEAD: <script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.5/js/bootstrap.min.js"></script>
#+HTML_HEAD: <style type="text/css">
#+HTML_HEAD:   footer {background-color: #111 !important;}
#+HTML_HEAD:   pre {background-color: #111; color: #ccc;}
#+HTML_HEAD: </style>

* General
- This program is free software: released under Creative Commons Zero
  (CC0) license

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

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

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

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

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

- See [[https://www3.svjatoslav.eu/projects/sixth-3d/apidocs/][JavaDoc]].

* Project description
+ See: [[https://www3.svjatoslav.eu/projects/sixth-3d-demos/][demos of current 3D engine capabilities]]

[[id:d03013e5-931b-40ca-bc4b-e4b3f23b9a4e][In software]], [[id:a11f7150-1b25-4ca4-a3c3-8c8bd1352bd4][pure Java]] realtime 3D rendering engine. With the final
goal of becoming a platform for buildng 3D user interfaces and
interactive data visualization for [[https://www3.svjatoslav.eu/projects/sixth/][project Sixth]].

Sixth 3D can be also used as standalone [[id:08f71987-90af-40dc-bb65-bac87db9e652][3D engine in your project]].

** Justification for software rendering
   :PROPERTIES:
   :ID:       d03013e5-931b-40ca-bc4b-e4b3f23b9a4e
   :END:
3D rendering is done in software, 100% pure Java on CPU. At least for
now. Modern CPU cores count keeps growing and therefore rendering by
CPU is not as expensive as it used to be for the old single core
systems.

CPU rendering performance is already good enough to implement usable
3D UI at sufficient detail level, resolution and frame rate.

Also CPU rendering allows to freely test different rendering and
optimization algorithms and retains complete control of every rendered
pixel.
** Justification for Java
   :PROPERTIES:
   :ID:       a11f7150-1b25-4ca4-a3c3-8c8bd1352bd4
   :END:
- It is easy to refactor and experiment with.

- Easy portability and installation. No need to deal with platform
  specific dependencies.

- It scales well to handle great complexity.
  - Allows to implement clever performance optimizations (instead of
    going for GPU offered brute-force rendering approach).

- No limitations imposed by:
  - requirement for decent GPU
  - GPU missing features
  - GPU missing/incomplete/buggy drivers
  - OpenGL specification

- It is fast enough thanks to:
  - Java virtual machine just-in-time compiler.
  - Growing CPU cores count.

- As a result it is easy to run on various hardware platforms and
  operating systems.

* API documentation
- See [[https://www3.svjatoslav.eu/projects/sixth-3d/apidocs/][JavaDoc]].

Note: due to a lack of time, there is still big room for improvement
on documentation.

So far best resource is to download and explore source code for:
+ 3D engine ([[https://www3.svjatoslav.eu/projects/sixth-3d/graphs/][generated code graphs]] (generated using [[https://www3.svjatoslav.eu/projects/javainspect/][JavaInspect]]))
+ For API usage examples, see [[https://www3.svjatoslav.eu/projects/sixth-3d-demos/][demos]]
* Instructions to embed Sixth-3D in your project
  :PROPERTIES:
  :ID:       08f71987-90af-40dc-bb65-bac87db9e652
  :END:
Maven *pom.xml* file snippet:
#+BEGIN_SRC xml
<dependencies>
    ...
    <dependency>
        <groupId>eu.svjatoslav</groupId>
        <artifactId>sixth-3d</artifactId>
        <version>1.2</version>
    </dependency>
    ...
</dependencies>

<repositories>
    ...
    <repository>
        <id>svjatoslav.eu</id>
        <name>Svjatoslav repository</name>
        <url>http://www3.svjatoslav.eu/maven/</url>
    </repository>
    ...
</repositories>
#+END_SRC

For API usage examples, see [[https://www3.svjatoslav.eu/projects/sixth-3d-demos/][demos]].
* TODO features to add
+ read this as example, and apply improvements/fixes where applicable:
  http://blog.rogach.org/2015/08/how-to-create-your-own-simple-3d-render.html

+ Improve triangulation. Read: https://ianthehenry.com/posts/delaunay/

+ Partial region/frame repaint: when only one small object changed on
  the scene, it would be faster to re-render that specific area.

+ Once partial rendering works, in would be easy to add multi-core
  rendering support. So that each core renders it's own region of the
  screen.

+ Antialiazing. Would improve text readability. If antialiazing is too
  expensive for every frame, it could be used only for last frame
  before animations become still and waiting for user input starts.
** Render only visible polygons
+ This would significantly reduce RAM <-> CPU traffic.

+ General algorithm description:
  + For each horizontal scanline:
    + sort polygon edges from left to right
    + while iterating and drawing pixels over screen X axis (left to
      right) track next appearing/disappearing polygons.
      + For each polygon edge update Z sorted active polygons list.
      + Only draw pixel from the top-most polygon.
        + Only if polygon area is transparent/half-transparent add
          colors from the polygons below.

+ As a bonus, this would allow to track which polygons are really
  visible in the final scene for each frame.

  + Such information allows further optimizations:

    + Dynamic geometry simplification:
      + Dynamically detect and replace invisible objects from the
        scene with simplified bounding box.

      + Dynamically replace boudnig box with actual object once it
        becomes visible.

    + Dynamically unload unused textures from RAM.