# Overview

```+--------------------------------------------+
| 3D Parametric Plotter for the Raspberry Pi |
+--------------------------------------------+

WARNING: ------------------------------------------------------------------+
| Use this program at your own risk!                                       |
| No seriously bad things have happened on clean installations without     |
| overclocking, but some users with specific set-ups did have some issues. |
| If you have any important data on your Raspberry Pi, it's a good idea to |
| back that up before running this program.                                |
+--------------------------------------------------------------------------+

0. Overview
1. Compilation
2. Usage
3. Bugs

0. Overview
===========

Surfaces in three-dimensional space can be described by a function which maps
values from a two-dimensional plane (u,v-coordinates) into 3D space (x,y,z).

Playing around with these functions can be fun and you can get some very pretty
surfaces with relatively concise formulas.

I wrote this program as a tool to play around with these, but also as an
exercise in OpenGL ES and parsing of mathematical expressions.

Also, I find it extraordinarily awesome that the Raspberry Pi can do this.

See a video demonstration here:

1. Compilation
==============

The program depends on GL, GLM and SDL, so make sure you have those installed
on your system before proceeding.  On Raspbian, this command should do it:
\$ sudo apt-get install libglm-dev libsdl1.2-dev

If you have everything, executing the following should compile the program:
\$ make

2. Usage
========

The output of
\$ ./rpi-simple-paramplot -h
shows the following:

Usage: ./rpi-simple-paramplot [options]
Options:
-e <vardef>
Define an auxiliary variable which can be used in following occurrences
of -e, -x, -y and -z.  The definition may use u and v.  The option argument
must be of the form "<varchar>=<definition>" with the '=' sign exactly at
the second position (no whitespace before it!)
-x <xdef>, -y <ydef>, -z <zdef>
Specify the parametric function to plot.  u, v and user-defined variables
may be used.
-r <rdef>, -g <gdef>, -b <bdef>
Specify the color of the surface.  u, v and user-defined variables
may be used.
-u <u_res>, -v <v_res>
Set the number of sampling points along the u and v coordinates.
The default is 64, 64.
Examples:
Sphere:
./rpi-simple-paramplot -e "U=2*pi*u" -e "V=pi*v" \
-x "cos(U) * sin(V)" -z "sin(U) * sin(V)" -y "cos(V)";
Colorful rotaty-whirly thing:
./rpi-simple-paramplot -u512 -v32 \
-e U=2*pi*u -e V=2*pi*v -e "R=1" -e "r=.25" \
-x "cos(5*U) * (R + r*sin(V) + 2*r*cos(U))" \
-y "sin(5*U) * (R + r*sin(V) + 2*r*cos(U))" \
-z ".2*r*cos(V) + 5*r*sin(U)" \
-r ".5 + .5*sin(U)" -g ".5 + .5*sin(2*U)" -b ".5 + .5*sin(5*U)"

When the program is running, you can use the following keys and buttons:
Left Mouse Button, Arrow Keys:            Rotate view.
Right Mouse Button:                       Roll view.
Middle Mouse Button, Wheel, Page Up/Down: Move view forward/backward.
Escape: Quit program.
F1:     Print keybindings.
F2:     Toggle vertical synchronization.
F3:     Toggle backface culling (can be used to enhance performance,
but only with correctly oriented closed surfaces).
F4:     Toggle wireframe rendering.

3. Bugs
=======

Enabling overscan settings in the RPi config may cause a black screen until
the next reboot with overscan disabled.  Testing and reproduction needed.
Apparently SDL_SetVideoMode segfaults.  Doesn't seem to happen in X11.

Combinations of overclocking and null divisions have in one case lead to
instant reboots and some filesystem corruption, although this might have
been caused by an already corrupt system.

Compiling with -O3 optimization causes some very very weird floating point
operation results which leads to the camera spazzing out.  You can compile
everything except graphics.cpp with -O3 for a great performance boost though.

Have fun math-ing on your Raspberry Pi!
- Benedek Vartok  <vartokb@ethz.ch>
```