renderer: add area sampling scaling method (#201)

Adds Area Sampling to the list of scaling options. Works well to achieve a high-quality, smooth super-sampling effect. Dolphin has had this for a while and so has Ryujinx, so lui decided to port it.

Adapted from these two PRs:
https://github.com/Ryujinx/Ryujinx/pull/7304
https://github.com/dolphin-emu/dolphin/pull/11999

Credit: Torzu, lui

Reviewed-on: http://vub63vv26q6v27xzv2dtcd25xumubshogm67yrpaz2rculqxs7jlfqad.onion/torzu-emu/torzu/pulls/57
Co-authored-by: lui <lui@vub63vv26q6v27xzv2dtcd25xumubshogm67yrpaz2rculqxs7jlfqad.onion>
Co-committed-by: lui <lui@vub63vv26q6v27xzv2dtcd25xumubshogm67yrpaz2rculqxs7jlfqad.onion>

Co-authored-by: lui <lui@vub63vv26q6v27xzv2dtcd25xumubshogm67yrpaz2rculqxs7jlfqad.onion>
Co-authored-by: crueter <swurl@swurl.xyz>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/201
Co-authored-by: JPikachu <jpikachu.eden@gmail.com>
Co-committed-by: JPikachu <jpikachu.eden@gmail.com>

src/android/app/src/main/java/org/yuzu/yuzu_emu/features/settings/ui/SettingsFragmentPresenter.kt

@@ -220,6 +220,7 @@ class SettingsFragmentPresenter(
 
     private fun addGraphicsSettings(sl: ArrayList<SettingsItem>) {
         sl.apply {
+            // TODO(crueter): reorganize this, this is awful
             add(IntSetting.RENDERER_ACCURACY.key)
             add(IntSetting.RENDERER_RESOLUTION.key)
             add(IntSetting.RENDERER_VSYNC.key)

src/android/app/src/main/res/values/arrays.xml

@@ -250,6 +250,7 @@
         <item>@string/scaling_filter_gaussian</item>
         <item>@string/scaling_filter_scale_force</item>
         <item>@string/scaling_filter_fsr</item>
+        <item>@string/scaling_filter_area</item>
     </string-array>
 
     <integer-array name="rendererScalingFilterValues">
@@ -259,6 +260,7 @@
         <item>3</item>
         <item>4</item>
         <item>5</item>
+        <item>6</item>
     </integer-array>
 
     <string-array name="rendererAntiAliasingNames">

src/android/app/src/main/res/values/strings.xml

@@ -863,6 +863,7 @@
     <string name="scaling_filter_gaussian">Gaussian</string>
     <string name="scaling_filter_scale_force">ScaleForce</string>
     <string name="scaling_filter_fsr">AMD FidelityFX™ Super Resolution</string>
+    <string name="scaling_filter_area">Area</string>
 
     <!-- Anti-Aliasing -->
     <string name="anti_aliasing_none">None</string>

src/common/settings_enums.h

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -158,7 +164,7 @@ ENUM(ResolutionSetup,
      Res7X,
      Res8X);
 
-ENUM(ScalingFilter, NearestNeighbor, Bilinear, Bicubic, Gaussian, ScaleForce, Fsr, MaxEnum);
+ENUM(ScalingFilter, NearestNeighbor, Bilinear, Bicubic, Gaussian, ScaleForce, Fsr, Area, MaxEnum);
 
 ENUM(AntiAliasing, None, Fxaa, Smaa, MaxEnum);
 

src/video_core/host_shaders/CMakeLists.txt

@@ -42,6 +42,7 @@ set(SHADER_FILES
     opengl_present_scaleforce.frag
     opengl_smaa.glsl
     pitch_unswizzle.comp
+    present_area.frag
     present_bicubic.frag
     present_gaussian.frag
     queries_prefix_scan_sum.comp

src/video_core/host_shaders/present_area.frag

@@ -0,0 +1,107 @@
+#version 460 core
+
+layout(location = 0) in vec2 frag_tex_coord;
+layout(location = 0) out vec4 color;
+layout(binding = 0) uniform sampler2D color_texture;
+
+#ifdef VULKAN
+
+struct ScreenRectVertex {
+    vec2 position;
+    vec2 tex_coord;
+};
+layout (push_constant) uniform PushConstants {
+    mat4 modelview_matrix;
+    ScreenRectVertex vertices[4];
+};
+
+#else // OpenGL
+
+layout(location = 1) uniform uvec2 screen_size;
+
+#endif
+
+/***** Area Sampling *****/
+
+// By Sam Belliveau and Filippo Tarpini. Public Domain license.
+// Effectively a more accurate sharp bilinear filter when upscaling,
+// that also works as a mathematically perfect downscale filter.
+// https://entropymine.com/imageworsener/pixelmixing/
+// https://github.com/obsproject/obs-studio/pull/1715
+// https://legacy.imagemagick.org/Usage/filter/
+vec4 AreaSampling(sampler2D textureSampler, vec2 texCoords, vec2 source_size, vec2 target_size) {
+    // Determine the sizes of the source and target images.
+    vec2 inverted_target_size = vec2(1.0) / target_size;
+
+    // Determine the range of the source image that the target pixel will cover.
+    vec2 range = source_size * inverted_target_size;
+    vec2 beg = (texCoords.xy * source_size) - (range * 0.5);
+    vec2 end = beg + range;
+
+    // Compute the top-left and bottom-right corners of the pixel box.
+    ivec2 f_beg = ivec2(floor(beg));
+    ivec2 f_end = ivec2(floor(end));
+
+    // Compute how much of the start and end pixels are covered horizontally & vertically.
+    float area_w = 1.0 - fract(beg.x);
+    float area_n = 1.0 - fract(beg.y);
+    float area_e = fract(end.x);
+    float area_s = fract(end.y);
+
+    // Compute the areas of the corner pixels in the pixel box.
+    float area_nw = area_n * area_w;
+    float area_ne = area_n * area_e;
+    float area_sw = area_s * area_w;
+    float area_se = area_s * area_e;
+
+    // Initialize the color accumulator.
+    vec4 avg_color = vec4(0.0, 0.0, 0.0, 0.0);
+
+    // Accumulate corner pixels.
+    avg_color += area_nw * texelFetch(textureSampler, ivec2(f_beg.x, f_beg.y), 0);
+    avg_color += area_ne * texelFetch(textureSampler, ivec2(f_end.x, f_beg.y), 0);
+    avg_color += area_sw * texelFetch(textureSampler, ivec2(f_beg.x, f_end.y), 0);
+    avg_color += area_se * texelFetch(textureSampler, ivec2(f_end.x, f_end.y), 0);
+
+    // Determine the size of the pixel box.
+    int x_range = int(f_end.x - f_beg.x - 0.5);
+    int y_range = int(f_end.y - f_beg.y - 0.5);
+
+    // Accumulate top and bottom edge pixels.
+    for (int x = f_beg.x + 1; x <= f_beg.x + x_range; ++x) {
+        avg_color += area_n * texelFetch(textureSampler, ivec2(x, f_beg.y), 0);
+        avg_color += area_s * texelFetch(textureSampler, ivec2(x, f_end.y), 0);
+    }
+
+    // Accumulate left and right edge pixels and all the pixels in between.
+    for (int y = f_beg.y + 1; y <= f_beg.y + y_range; ++y) {
+        avg_color += area_w * texelFetch(textureSampler, ivec2(f_beg.x, y), 0);
+        avg_color += area_e * texelFetch(textureSampler, ivec2(f_end.x, y), 0);
+
+        for (int x = f_beg.x + 1; x <= f_beg.x + x_range; ++x) {
+            avg_color += texelFetch(textureSampler, ivec2(x, y), 0);
+        }
+    }
+
+    // Compute the area of the pixel box that was sampled.
+    float area_corners = area_nw + area_ne + area_sw + area_se;
+    float area_edges = float(x_range) * (area_n + area_s) + float(y_range) * (area_w + area_e);
+    float area_center = float(x_range) * float(y_range);
+
+    // Return the normalized average color.
+    return avg_color / (area_corners + area_edges + area_center);
+}
+
+void main() {
+    vec2 source_image_size = textureSize(color_texture, 0);
+    vec2 window_size;
+
+    #ifdef VULKAN
+    window_size.x = vertices[1].position.x - vertices[0].position.x;
+    window_size.y = vertices[2].position.y - vertices[0].position.y;
+    #else // OpenGL
+    window_size = screen_size;
+    #endif
+
+    color = AreaSampling(color_texture, frag_tex_coord, source_image_size, window_size);
+}

src/video_core/renderer_opengl/gl_blit_screen.cpp

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -86,6 +92,9 @@ void BlitScreen::CreateWindowAdapt() {
     case Settings::ScalingFilter::ScaleForce:
         window_adapt = MakeScaleForce(device);
         break;
+    case Settings::ScalingFilter::Area:
+        window_adapt = MakeArea(device);
+        break;
     case Settings::ScalingFilter::Fsr:
     case Settings::ScalingFilter::Bilinear:
     default:

src/video_core/renderer_opengl/present/filters.cpp

@@ -1,8 +1,15 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include "video_core/host_shaders/opengl_present_frag.h"
 #include "video_core/host_shaders/opengl_present_scaleforce_frag.h"
+#include "video_core/host_shaders/present_area_frag.h"
 #include "video_core/host_shaders/present_bicubic_frag.h"
 #include "video_core/host_shaders/present_gaussian_frag.h"
 #include "video_core/renderer_opengl/present/filters.h"
@@ -36,4 +43,9 @@ std::unique_ptr<WindowAdaptPass> MakeScaleForce(const Device& device) {
         fmt::format("#version 460\n{}", HostShaders::OPENGL_PRESENT_SCALEFORCE_FRAG));
 }
 
+std::unique_ptr<WindowAdaptPass> MakeArea(const Device& device) {
+    return std::make_unique<WindowAdaptPass>(device, CreateBilinearSampler(),
+                                             HostShaders::PRESENT_AREA_FRAG);
+}
+
 } // namespace OpenGL

src/video_core/renderer_opengl/present/filters.h

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -13,5 +19,6 @@ std::unique_ptr<WindowAdaptPass> MakeBilinear(const Device& device);
 std::unique_ptr<WindowAdaptPass> MakeBicubic(const Device& device);
 std::unique_ptr<WindowAdaptPass> MakeGaussian(const Device& device);
 std::unique_ptr<WindowAdaptPass> MakeScaleForce(const Device& device);
+std::unique_ptr<WindowAdaptPass> MakeArea(const Device& device);
 
 } // namespace OpenGL

src/video_core/renderer_opengl/present/present_uniforms.h

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -10,6 +16,7 @@ namespace OpenGL {
 constexpr GLint PositionLocation = 0;
 constexpr GLint TexCoordLocation = 1;
 constexpr GLint ModelViewMatrixLocation = 0;
+constexpr GLint ScreenSizeLocation = 1;
 
 struct ScreenRectVertex {
     constexpr ScreenRectVertex() = default;

src/video_core/renderer_opengl/present/window_adapt_pass.cpp

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -110,6 +116,9 @@ void WindowAdaptPass::DrawToFramebuffer(ProgramManager& program_manager, std::li
         glBindTextureUnit(0, textures[i]);
         glProgramUniformMatrix3x2fv(vert.handle, ModelViewMatrixLocation, 1, GL_FALSE,
                                     matrices[i].data());
+        glProgramUniform2ui(frag.handle, ScreenSizeLocation,
+                            static_cast<GLuint>(layout.screen.GetWidth()),
+                            static_cast<GLuint>(layout.screen.GetHeight()));
         glNamedBufferSubData(vertex_buffer.handle, 0, sizeof(vertices[i]), std::data(vertices[i]));
         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
     }

src/video_core/renderer_vulkan/present/filters.cpp

@@ -1,8 +1,15 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include "common/common_types.h"
 
+#include "video_core/host_shaders/present_area_frag_spv.h"
 #include "video_core/host_shaders/present_bicubic_frag_spv.h"
 #include "video_core/host_shaders/present_gaussian_frag_spv.h"
 #include "video_core/host_shaders/vulkan_present_frag_spv.h"
@@ -53,4 +60,9 @@ std::unique_ptr<WindowAdaptPass> MakeScaleForce(const Device& device, VkFormat f
                                              SelectScaleForceShader(device));
 }
 
+std::unique_ptr<WindowAdaptPass> MakeArea(const Device& device, VkFormat frame_format) {
+    return std::make_unique<WindowAdaptPass>(device, frame_format, CreateBilinearSampler(device),
+                                             BuildShader(device, PRESENT_AREA_FRAG_SPV));
+}
+
 } // namespace Vulkan

src/video_core/renderer_vulkan/present/filters.h

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -14,5 +20,6 @@ std::unique_ptr<WindowAdaptPass> MakeBilinear(const Device& device, VkFormat fra
 std::unique_ptr<WindowAdaptPass> MakeBicubic(const Device& device, VkFormat frame_format);
 std::unique_ptr<WindowAdaptPass> MakeGaussian(const Device& device, VkFormat frame_format);
 std::unique_ptr<WindowAdaptPass> MakeScaleForce(const Device& device, VkFormat frame_format);
+std::unique_ptr<WindowAdaptPass> MakeArea(const Device& device, VkFormat frame_format);
 
 } // namespace Vulkan

src/video_core/renderer_vulkan/vk_blit_screen.cpp

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -43,6 +49,9 @@ void BlitScreen::SetWindowAdaptPass() {
     case Settings::ScalingFilter::ScaleForce:
         window_adapt = MakeScaleForce(device, swapchain_view_format);
         break;
+    case Settings::ScalingFilter::Area:
+        window_adapt = MakeArea(device, swapchain_view_format);
+        break;
     case Settings::ScalingFilter::Fsr:
     case Settings::ScalingFilter::Bilinear:
     default:

src/yuzu/configuration/shared_translation.cpp

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -536,6 +542,7 @@ std::unique_ptr<ComboboxTranslationMap> ComboboxEnumeration(QWidget* parent)
                               PAIR(ScalingFilter, Gaussian, tr("Gaussian")),
                               PAIR(ScalingFilter, ScaleForce, tr("ScaleForce")),
                               PAIR(ScalingFilter, Fsr, tr("AMD FidelityFX™️ Super Resolution")),
+                              PAIR(ScalingFilter, Area, tr("Area")),
                           }});
     translations->insert({Settings::EnumMetadata<Settings::AntiAliasing>::Index(),
                           {

src/yuzu/configuration/shared_translation.h

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -40,6 +46,7 @@ static const std::map<Settings::ScalingFilter, QString> scaling_filter_texts_map
     {Settings::ScalingFilter::ScaleForce,
      QStringLiteral(QT_TRANSLATE_NOOP("GMainWindow", "ScaleForce"))},
     {Settings::ScalingFilter::Fsr, QStringLiteral(QT_TRANSLATE_NOOP("GMainWindow", "FSR"))},
+    {Settings::ScalingFilter::Area, QStringLiteral(QT_TRANSLATE_NOOP("GMainWindow", "Area"))},
 };
 
 static const std::map<Settings::ConsoleMode, QString> use_docked_mode_texts_map = {