diff options
Diffstat (limited to 'fft.shader')
| -rw-r--r-- | fft.shader | 67 |
1 files changed, 26 insertions, 41 deletions
@@ -24,6 +24,8 @@ Shader "yum_food/fft" #pragma fragment frag #include "UnityCG.cginc" + #define RADIX 16 + #define N 256 #define GPU_FFT_RADIX16 #define GPU_FFT_RADIX16_N256 #include "fft_twiddle_tables.cginc" @@ -106,6 +108,13 @@ Shader "yum_food/fft" return dot(color, float3(0.2126, 0.7152, 0.0722)); } + float4 cmul_2x(float4 a, float2 b) { + float4 r; + r.xz = a.xz * b.x - a.yw * b.y; + r.yw = a.xz * b.y + a.yw * b.x; + return r; + } + fixed4 frag (v2f i) : SV_Target { // Extract coordinates @@ -150,80 +159,56 @@ Shader "yum_food/fft" const int idx_in_wing = idx_in_group % i.span; // Main DFT loop - float sum_real = 0.0; - float sum_imag = 0.0; - for (int j = 0; j < _Radix; j++) + float4 sum = float4(0.0, 0.0, 0.0, 0.0); + for (int j = 0; j < RADIX; j++) { // Calculate input position const int input_pos = group * i.butterfly_size + j * i.span + idx_in_wing; // Read input value - float in_real, in_imag; + float4 input_tex; if (is_row_stage) { - const float2 input_uv = float2((input_pos + 0.5) / (float)_N, i.uv.y); - const float4 input_tex = _MainTex.SampleLevel(point_clamp_s, input_uv, 0); - if (_Stage == 0 && _Inverse < 0.5) { - // Assume that input is grayscale and real-valued. - in_real = input_tex.x; - in_imag = 0; - } else { - in_real = input_tex.x; - in_imag = input_tex.y; - } + const float2 input_uv = float2((input_pos + 0.5) / (float)N, i.uv.y); + input_tex = _MainTex.SampleLevel(point_clamp_s, input_uv, 0); } else { - float2 input_uv = float2(i.uv.x, (input_pos + 0.5) / (float)_N); - float4 input_tex = _MainTex.SampleLevel(point_clamp_s, input_uv, 0); - in_real = input_tex.x; - in_imag = input_tex.y; + const float2 input_uv = float2(i.uv.x, (input_pos + 0.5) / (float)N); + input_tex = _MainTex.SampleLevel(point_clamp_s, input_uv, 0); } // Read DFT coefficient - const float2 coeff = _Inverse > 0.5 ? IDFT_MATRIX[wing][j] : DFT_MATRIX[wing][j]; - const float coeff_real = coeff.x; - const float coeff_imag = coeff.y; + const float2 coeff = _Inverse ? IDFT_MATRIX[wing][j] : DFT_MATRIX[wing][j]; // Complex multiply-accumulate - sum_real += coeff_real * in_real - coeff_imag * in_imag; - sum_imag += coeff_real * in_imag + coeff_imag * in_real; + sum += cmul_2x(input_tex, coeff); } // Apply stage twiddle if needed - float out_real, out_imag; + float4 out_val; if (wing > 0 && idx_in_wing > 0) { const int twiddle_idx = wing * idx_in_wing; float2 tw; if (_Stage % 2 == 0) { - tw = _Inverse > 0.5 ? STAGE0_TWIDDLES_INV[twiddle_idx] : STAGE0_TWIDDLES[twiddle_idx]; + tw = _Inverse ? STAGE0_TWIDDLES_INV[twiddle_idx] : STAGE0_TWIDDLES[twiddle_idx]; } else { - tw = _Inverse > 0.5 ? STAGE1_TWIDDLES_INV[twiddle_idx] : STAGE1_TWIDDLES[twiddle_idx]; + tw = _Inverse ? STAGE1_TWIDDLES_INV[twiddle_idx] : STAGE1_TWIDDLES[twiddle_idx]; } - float tw_real = tw.x; - float tw_imag = tw.y; - // Output = twiddle * sum - out_real = tw_real * sum_real - tw_imag * sum_imag; - out_imag = tw_real * sum_imag + tw_imag * sum_real; + out_val = cmul_2x(sum, tw); } else { - out_real = sum_real; - out_imag = sum_imag; + out_val = sum; } - - // Handle final stage of inverse FFT - if (_Inverse > 0.5 && _Stage == i.num_stages_per_dim * 2 - 1) { - float normalized = out_real / (_N * _N); - return float4(normalized, normalized, normalized, 1); + if (_Inverse && _Stage == 3) { + out_val /= (_N * _N); } - - // Pack complex result into RGBA - return float4(out_real, out_imag, 0, 1); + return out_val; } ENDCG } |