Duckstation/data/resources/shaders/reshade/Shaders/crt-royale/lib/downsampling-functions.fxh

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#ifndef _DOWNSAMPLING_FUNCTIONS_H
#define _DOWNSAMPLING_FUNCTIONS_H
///////////////////////////////// MIT LICENSE ////////////////////////////////
// Copyright (C) 2020 Alex Gunter <akg7634@gmail.com>
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.
float3 opaque_linear_downsample(
const sampler2D tex,
const float2 texcoord,
const uint num_pairs,
const float2 delta_uv
) {
const uint total_num_samples = num_pairs * 2 + 1;
const float2 coord_left = texcoord - delta_uv * num_pairs;
float3 acc = 0;
for(int i = 0; i < total_num_samples; i++) {
const float2 coord = coord_left + i * delta_uv;
acc += tex2D_nograd(tex, coord).rgb;
}
return acc / total_num_samples;
}
float3 opaque_lanczos_downsample(
const sampler2D tex,
const float2 texcoord,
const uint num_pairs,
const float2 delta_uv,
const float num_sinc_lobes,
const float weight_at_center
) {
const uint total_num_samples = num_pairs * 2 + 1;
const float2 coord_left = texcoord - delta_uv * num_pairs;
const float sinc_dx = num_sinc_lobes / num_pairs; // 2 * num_sinc_lobes / (total_num_samples - 1)
float3 acc = 0;
float w_sum = 0;
for(int i = 0; i < total_num_samples; i++) {
const float2 coord = coord_left + i * delta_uv;
const float sinc_x = i * sinc_dx;
const float weight = (i != num_pairs) ?
num_sinc_lobes * sin(pi*sinc_x) * sin(pi*sinc_x/num_sinc_lobes) / (pi*pi * sinc_x*sinc_x) :
weight_at_center;
acc += weight * tex2D_nograd(tex, coord).rgb;
w_sum += weight;
}
return acc / w_sum;
}
float3 opaque_lanczos_downsample(
const sampler2D tex,
const float2 texcoord,
const uint num_pairs,
const float2 delta_uv,
const float num_sinc_lobes
) {
return opaque_lanczos_downsample(tex, texcoord, num_pairs, delta_uv, num_sinc_lobes, 1);
}
#endif // _DOWNSAMPLING_FUNCTIONS_H