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Does UE4 use real input FFT? Is this why FFT spectral texture size is (N/2 + 1) * 2?

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    Does UE4 use real input FFT? Is this why FFT spectral texture size is (N/2 + 1) * 2?

    Hello,

    I have questions about UE4's FFT details.

    I have noticed that UE4's Bloom post-process is using FFT.

    I saw two-for-one trick which transforms 'r & b' channels into one complex signal 'r + i * g'.

    So I thought This FFT module's input would be a complex number.

    But the output of the FFT is the size of (N/2 + 1) * 2.

    I am not sure how UE4's FFT module works.

    Could anyone help me with this?

    I am trying to implement a post-processing shader that ought to calculate in the spectral domain and

    make a summation of multiple results of calculation and then IFFT.

    To do that I could be able to make FFT which could get an input of a complex number.

    Thank you.
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