Add texel anti-aliasing

builtin/settingtypes.txt

@@ -628,6 +628,11 @@ antialiasing (Antialiasing method) enum none none,fsaa,ssaa
 #    Value of 2 means taking 2x2 = 4 samples.
 fsaa (Anti-aliasing scale) enum 2 2,4,8,16
 
+#    Anti-alias texel edges by using bilinear texture sampling together with a
+#    sample coordinate transformation in the shader.
+#    This setting is ONLY applied if bilinear_filter or trilinear_filter is enabled.
+texel_antialiasing (Texel anti-aliasing) bool true
+
 #    Applies a post-processing filter to detect and smoothen high-contrast edges.
 #    Provides balance between speed and image quality.
 #    fxaa can used in combination with the other anti-aliasing methods
@@ -2067,9 +2072,12 @@ array_texture_max (Array texture max layers) int 65535 0 65535
 #    can be blurred, so this option automatically upscales them to preserve
 #    crisp pixels. This defines the minimum texture size for the upscaled textures;
 #    higher values look sharper, but require more memory.
-#    This setting is ONLY applied if any of the mentioned filters are enabled.
+#    This setting is ONLY applied if any of the mentioned filters are enabled and
+#    texel_antialiasing is disabled.
 #    This is also used as the base node texture size for world-aligned
 #    texture autoscaling.
+#
+#    Requires: !texel_antialiasing
 texture_min_size (Base texture size) int 192 192 16384
 
 #    Side length of a cube of map blocks that the client will consider together

client/shaders/nodes_shader/opengl_fragment.glsl

@@ -3,6 +3,9 @@
 #else
 	uniform sampler2D baseTexture;
 #endif
+#ifdef TEXEL_ANTIALIASING
+	uniform vec2 texelSize0;
+#endif
 #define crackTexture texture1
 uniform sampler2D crackTexture;
 
@@ -432,14 +435,41 @@ vec2 uv_repeat(vec2 v)
 	return v;
 }
 
+#ifdef TEXEL_ANTIALIASING
+
+// Move the uv coordinates within the texel such that when sampling the texture
+// with bilinear filtering, the result looks like nearest neighbour sampling
+// with anti-aliased texels.
+// Based on t3ssel8r's code from https://www.patreon.com/posts/83276362.
+vec2 uv_texel_antialias()
+{
+	vec2 box_size = clamp(0.7 * fwidth(varTexCoord.st) / texelSize0, 1e-5, 1.0);
+	vec2 tx = varTexCoord.st / texelSize0 - 0.5 * box_size;
+	vec2 tx_off = clamp((fract(tx) - (1.0 - box_size)) / box_size, 0.0, 1.0);
+	return (floor(tx) + 0.5 + tx_off) * texelSize0;
+}
+
+#endif
+
 void main(void)
 {
-	vec2 uv = varTexCoord.st;
+#ifdef TEXEL_ANTIALIASING
+	vec2 uv = uv_texel_antialias();
+#ifdef USE_ARRAY_TEXTURE
+	vec4 base = textureGrad(baseTexture, vec3(uv, varTexLayer),
+		dFdx(varTexCoord.st), dFdy(varTexCoord.st)).rgba;
+#else
+	// For the deprecated texture2D there is no texture2DGrad
+	vec4 base = texture2D(baseTexture, uv).rgba;
+#endif
 
+#else
+	vec2 uv = varTexCoord.st;
 #ifdef USE_ARRAY_TEXTURE
 	vec4 base = texture(baseTexture, vec3(uv, varTexLayer)).rgba;
 #else
 	vec4 base = texture2D(baseTexture, uv).rgba;
+#endif
 #endif
 
 	// Handle transparency by discarding pixel as appropriate.

client/shaders/object_shader/opengl_fragment.glsl

@@ -3,6 +3,9 @@
 #else
 	uniform sampler2D baseTexture;
 #endif
+#ifdef TEXEL_ANTIALIASING
+	uniform vec2 texelSize0;
+#endif
 
 uniform vec3 dayLight;
 uniform lowp vec4 fogColor;
@@ -362,15 +365,36 @@ float getShadow(sampler2D shadowsampler, vec2 smTexCoord, float realDistance)
 #endif
 #endif
 
+#ifdef TEXEL_ANTIALIASING
+// Copied from the nodes fragment shader
+vec2 uv_texel_antialias()
+{
+	vec2 box_size = clamp(0.7 * fwidth(varTexCoord.st) / texelSize0, 1e-5, 1.0);
+	vec2 tx = varTexCoord.st / texelSize0 - 0.5 * box_size;
+	vec2 tx_off = clamp((fract(tx) - (1.0 - box_size)) / box_size, 0.0, 1.0);
+	return (floor(tx) + 0.5 + tx_off) * texelSize0;
+}
+#endif
+
 
 void main(void)
 {
-	vec2 uv = varTexCoord.st;
+#ifdef TEXEL_ANTIALIASING
+	vec2 uv = uv_texel_antialias();
+#ifdef USE_ARRAY_TEXTURE
+	vec4 base = textureGrad(baseTexture, vec3(uv, varTexLayer),
+		dFdx(varTexCoord.st), dFdy(varTexCoord.st)).rgba;
+#else
+	vec4 base = texture2D(baseTexture, uv).rgba;
+#endif
 
+#else
+	vec2 uv = varTexCoord.st;
 #ifdef USE_ARRAY_TEXTURE
 	vec4 base = texture(baseTexture, vec3(uv, varTexLayer)).rgba;
 #else
 	vec4 base = texture2D(baseTexture, uv).rgba;
+#endif
 #endif
 
 	// Handle transparency by discarding pixel as appropriate.

src/client/game.cpp

@@ -367,6 +367,11 @@ class NodeShaderConstantSetter : public IShaderConstantSetter
 
 		constants["ENABLE_WAVING_LEAVES"] = g_settings->getBool("enable_waving_leaves") ? 1 : 0;
 		constants["ENABLE_WAVING_PLANTS"] = g_settings->getBool("enable_waving_plants") ? 1 : 0;
+
+		if (g_settings->getBool("texel_antialiasing")
+				&& (g_settings->getBool("trilinear_filter")
+				|| g_settings->getBool("bilinear_filter")))
+			constants["TEXEL_ANTIALIASING"] = 1;
 	}
 };
 

src/client/imagesource.cpp

@@ -1499,8 +1499,8 @@ bool ImageSource::generateImagePart(std::string_view part_of_name,
 			 *    see <https://github.com/luanti-org/luanti/issues/15604> and related
 			 *    linked discussions.
 			 */
-			const bool filter = m_setting_trilinear_filter || m_setting_bilinear_filter;
-			if (filter) {
+			if (!m_setting_texel_antialiasing &&
+					(m_setting_trilinear_filter || m_setting_bilinear_filter)) {
 				const f32 scaleto = rangelim(g_settings->getU16("texture_min_size"),
 					TEXTURE_FILTER_MIN_SIZE, 16384);
 
@@ -1802,7 +1802,8 @@ ImageSource::ImageSource() :
 		m_setting_mipmap{g_settings->getBool("mip_map")},
 		m_setting_trilinear_filter{g_settings->getBool("trilinear_filter")},
 		m_setting_bilinear_filter{g_settings->getBool("bilinear_filter")},
-		m_setting_anisotropic_filter{g_settings->getBool("anisotropic_filter")}
+		m_setting_anisotropic_filter{g_settings->getBool("anisotropic_filter")},
+		m_setting_texel_antialiasing{g_settings->getBool("texel_antialiasing")}
 {}
 
 video::IImage* ImageSource::generateImage(std::string_view name,

src/client/imagesource.h

@@ -63,6 +63,7 @@ struct ImageSource {
 	bool m_setting_trilinear_filter;
 	bool m_setting_bilinear_filter;
 	bool m_setting_anisotropic_filter;
+	bool m_setting_texel_antialiasing;
 
 	// Cache of source images
 	SourceImageCache m_sourcecache;

src/defaultsettings.cpp

@@ -233,6 +233,7 @@ void set_default_settings()
 	settings->setDefault("opengl_debug", "true");
 #endif
 	settings->setDefault("fsaa", "2");
+	settings->setDefault("texel_antialiasing", "true");
 	settings->setDefault("undersampling", "1");
 	settings->setDefault("world_aligned_mode", "enable");
 	settings->setDefault("autoscale_mode", "disable");