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diff --git a/README.md b/README.md new file mode 100644 index 0000000..8ed5a42 --- /dev/null +++ b/README.md @@ -0,0 +1,31 @@ +## FFT on the GPU + +This is an optimized GPU-based 2D FFT for VRChat. It is only suitable for use +in worlds. + +### Quick start + +Run CPU simulator: + +```bash +$ cmake .. && cmake --build . && ./gpu_fft +``` + +Generate twiddle factor tables: + +```bash +$ python3 ./generate_twiddle_tables.py +``` + +### Overview + +`gpu_fft.cc` is a CPU simulator achieving high performance. It compares the GPU +algorithm against a simple radix-2 algorithm, demonstrating agreement within +some modest epsilons. Because higher radix FFTs do more sequential adds than +lower ffts, there is substantial error. In exchange, higher radices let you +compute FFTs with a shorter CRT chain. + +`generate_twiddle_tables.py` generates precomputes twiddle factors. +`DFT_MATRIX` corresponds to `ShaderUniforms.twiddle_factors` in the simulator +and `STAGE_TWIDDLES` corresponds to `ShaderUniforms.stage_twiddles`. + |