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README.md

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+# Batomorph
+
+This is a simple raytracer, written for POSIX systems in C23 with zero
+runtime dependencies (outside of the standard library).  To build with
+CMake:
+
+```sh
+cmake -B build
+cmake --build build
+```
+
+You may want to adjust the `NTHREADS` definition in `src/render.c` to
+match your system for best performance.
+
+When ran, the demo programs (`build/demo` and `build/rand`) will write
+the rendered image in sRGB
+[Farbfeld](https://tools.suckless.org/farbfeld/) to standard out.  For
+example:
+
+```sh
+build/demo > out.ff           # Produce Farbfeld file
+build/demo | ff2png > out.png # Produce PNG file
+build/demo | feh              # View directly
+```
+
+(Note that `ff2png` and `feh` are third-party programs)