Description

Line3D is the most efficient CPU-based 3D graphics engine ever written in Java. It is very lightweight and supports stereoscopic 3D rendering. Line3D is a part of PhysX3D, Nuclide3D, DroneEngine as well as KineticGas. Since there was no 3D graphics module in Java which could fill my needs of a very efficient graphics engine running on just one CPU core, I had to develop my own. I started with the very basic and very efficient Java libraries javax.swing.JFrame and java.awt.Graphics2D which provided basic shapes such as lines, circles, polygons as well as single pixels on the 2D screen area.
Then I implemented a coordinate transformation method which at first could only rotate, scale and transform 3D coordinates based on mouse interaction in order to project those on the 2D screen. Later the formulas for variable field of view were added. For better visualising plains and spheres I implemented simple polygon graphics with dynamic lighting by multiple light sources. Finally I implemented stereoscopic side-by-side image rendering for 3D monitors and head-mounted displays. Also a very efficient image post-processing algorithm was added to enable bloom.

Efficiency

Running sequential on just one CPU thread, the algorithms had to be as minimalistic and fast as possible. The framerate is depending only on how many lines or polygons are drawn on the display. At few objects, about 30000fps and for 50k objects 30fps can be achieved. Currently the amount of code is about 1k lines including mouse and keyboard interaction.

Choice of Algorithms

Problem 
My Solution
 
Alternative
Wireframe Rendering Stereoscopic Perspective Projection with adjustable field of view Orthographic Projection
Occlusion Painter's Algorithm z-Buffering
Shading Flat Shading with multiple light sources Phong Shading
The algorithms I choosed offer minimal computational effort due to their simplicity. Painter's Algorithm is much faster than z-Buffering as one only needs a single z-value per shape rather than per pixel and Flat Shading is much faster than Phong Shading. Because of this, the code can run in sequence and no GPU is required. The framerate does not depend on the screen resolution but rather on the number of objects to be drawn.

Frame Time Analysis of Typical Workload

Typical workload in PhysX3D: Shapes to be drawn (Lines, Circles, Polygons, Text): 46337
1. collect output data 0.00039ms
2. calculate shapes from 3D to 2D and save shapes in 2D 8.32303ms
3. sort shapes by z-coordinate 5.05169ms
4. draw shapes on frame buffer 14.37938ms
5. draw on screen display on frame buffer 0.06237ms
6. draw frame buffer on screen 1.02400ms
Total 34.52323fps 28.96482ms

Demo