C Graph Plotter (PPM + FFmpeg)

A C-based function graph plotter that renders mathematical expressions into PPM images and generates an animated video using ffmpeg.

The project supports runtime-defined mathematical functions using the TinyExpr expression parser.

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✨ Features

• Plot mathematical functions given as strings (e.g. sin(x), x^2, sqrt(x^2+1)).
• Runtime expression parsing using TinyExpr.
• Direct pixel-level rendering using the PPM (P6) image format.
• Animated horizontal zoom-out effect along the x-axis.
• Automatic MP4 video generation via ffmpeg.
• Cleans up intermediate PPM frames automatically.
• Minimal dependencies, fully written in C (C99).

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📦 Dependencies

Required

• C compiler (GCC or Clang, C99 compatible)
• ffmpeg

Included

• TinyExpr
  • tinyexpr.c
  • tinyexpr.h

TinyExpr is released under the zlib license and is included directly in this project.

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🧠 How It Works

1. Expression Parsing

   • The function is provided as a string.
   • TinyExpr parses and compiles the expression once.
   • The variable x is bound at evaluation time.

2. Coordinate Mapping

   • Mathematical coordinates (x, y) are mapped to pixel coordinates (px, py).
   • The x-range expands frame-by-frame, creating a horizontal zoom-out effect.
   • The y-range remains fixed to avoid visual bouncing.

3. Rendering

   • Each frame is rendered into a PPM image buffer.
   • X and Y axes are drawn when visible.
   • The function curve is plotted in pixel space.

4. Video Generation

   • All frames are combined into an MP4 video using ffmpeg.
   • Temporary PPM files are deleted automatically.

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🧮 Supported Expressions

Thanks to TinyExpr, the following are supported:

• Arithmetic operators: + - * / ^
• Math functions:
  • sin, cos, tan
  • sqrt, log, ln
  • abs, exp, etc.
• Constants: pi, e
• Variable binding: x

Examples

sin(x)
x^2
sqrt(x^2 + 1)
sin(x) * exp(-0.1*x)

🎥 Demo

output.mp4

Example animation plotting sinc(x) with horizontal zoom-out.