Return texture filter settings to previous state

This partially reverts commit 72ef90885d.

fixes #14007

builtin/settingtypes.txt

@@ -381,15 +381,15 @@ enable_3d_clouds (3D clouds) bool true
 
 [**Filtering and Antialiasing]
 
-#    Use mipmaps when scaling textures down. May slightly increase performance,
+#    Use mipmaps when scaling textures. May slightly increase performance,
 #    especially when using a high-resolution texture pack.
 #    Gamma-correct downscaling is not supported.
 mip_map (Mipmapping) bool false
 
-#    Use bilinear filtering when scaling textures down.
+#    Use bilinear filtering when scaling textures.
 bilinear_filter (Bilinear filtering) bool false
 
-#    Use trilinear filtering when scaling textures down.
+#    Use trilinear filtering when scaling textures.
 #    If both bilinear and trilinear filtering are enabled, trilinear filtering
 #    is applied.
 trilinear_filter (Trilinear filtering) bool false
@@ -1827,7 +1827,14 @@ world_aligned_mode (World-aligned textures mode) enum enable disable,enable,forc
 #    Warning: This option is EXPERIMENTAL!
 autoscale_mode (Autoscaling mode) enum disable disable,enable,force
 
-#    The base node texture size used for world-aligned texture autoscaling.
+#    When using bilinear/trilinear/anisotropic filters, low-resolution textures
+#    can be blurred, so automatically upscale them with nearest-neighbor
+#    interpolation to preserve crisp pixels. This sets the minimum texture size
+#    for the upscaled textures; higher values look sharper, but require more
+#    memory. Powers of 2 are recommended. This setting is ONLY applied if
+#    bilinear/trilinear/anisotropic filtering is enabled.
+#    This is also used as the base node texture size for world-aligned
+#    texture autoscaling.
 texture_min_size (Base texture size) int 64 1 32768
 
 #    Side length of a cube of map blocks that the client will consider together

src/client/content_cao.cpp

@@ -1381,6 +1381,13 @@ void GenericCAO::updateTextures(std::string mod)
 				material.Lighting = true;
 				material.BackfaceCulling = m_prop.backface_culling;
 
+				// don't filter low-res textures, makes them look blurry
+				// player models have a res of 64
+				const core::dimension2d<u32> &size = texture->getOriginalSize();
+				const u32 res = std::min(size.Height, size.Width);
+				use_trilinear_filter &= res > 64;
+				use_bilinear_filter &= res > 64;
+
 				material.forEachTexture([=] (auto &tex) {
 					setMaterialFilters(tex, use_bilinear_filter, use_trilinear_filter,
 							use_anisotropic_filter);

src/client/mesh.cpp

@@ -506,7 +506,8 @@ scene::IMesh* convertNodeboxesToMesh(const std::vector<aabb3f> &boxes,
 	return dst_mesh;
 }
 
-void setMaterialFilters(video::SMaterialLayer &tex, bool bilinear, bool trilinear, bool anisotropic) {
+void setMaterialFilters(video::SMaterialLayer &tex, bool bilinear, bool trilinear, bool anisotropic)
+{
 	if (trilinear)
 		tex.MinFilter = video::ETMINF_LINEAR_MIPMAP_LINEAR;
 	else if (bilinear)
@@ -514,9 +515,7 @@ void setMaterialFilters(video::SMaterialLayer &tex, bool bilinear, bool trilinea
 	else
 		tex.MinFilter = video::ETMINF_NEAREST_MIPMAP_NEAREST;
 
-	// "We don't want blurriness after all." ~ Desour, #13108
-	// (because of pixel art)
-	tex.MagFilter = video::ETMAGF_NEAREST;
+	tex.MagFilter = (trilinear || bilinear) ? video::ETMAGF_LINEAR : video::ETMAGF_NEAREST;
 
 	tex.AnisotropicFilter = anisotropic ? 0xFF : 0;
 }

src/client/tile.cpp

@@ -433,8 +433,10 @@ private:
 	// Maps image file names to loaded palettes.
 	std::unordered_map<std::string, Palette> m_palettes;
 
-	// Cached settings needed for making textures for meshes
-	bool m_mesh_texture_prefilter;
+	// Cached settings needed for making textures from meshes
+	bool m_setting_mipmap;
+	bool m_setting_trilinear_filter;
+	bool m_setting_bilinear_filter;
 };
 
 IWritableTextureSource *createTextureSource()
@@ -453,9 +455,9 @@ TextureSource::TextureSource()
 	// Cache some settings
 	// Note: Since this is only done once, the game must be restarted
 	// for these settings to take effect
-	m_mesh_texture_prefilter =
-			g_settings->getBool("mip_map") || g_settings->getBool("bilinear_filter") ||
-			g_settings->getBool("trilinear_filter") || g_settings->getBool("anisotropic_filter");
+	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");
 }
 
 TextureSource::~TextureSource()
@@ -700,7 +702,11 @@ video::ITexture* TextureSource::getTexture(const std::string &name, u32 *id)
 video::ITexture* TextureSource::getTextureForMesh(const std::string &name, u32 *id)
 {
 	// Avoid duplicating texture if it won't actually change
-	if (m_mesh_texture_prefilter)
+	static thread_local bool filter_needed =
+		m_setting_mipmap ||
+		((m_setting_trilinear_filter || m_setting_bilinear_filter) &&
+		g_settings->getS32("texture_min_size") > 1);
+	if (filter_needed)
 		return getTexture(name + "^[applyfiltersformesh", id);
 	return getTexture(name, id);
 }
@@ -1735,8 +1741,46 @@ bool TextureSource::generateImagePart(std::string part_of_name,
 			}
 
 			// Apply the "clean transparent" filter, if needed
-			if (m_mesh_texture_prefilter)
+			if (m_setting_mipmap)
 				imageCleanTransparent(baseimg, 127);
+
+			/* Upscale textures to user's requested minimum size.  This is a trick to make
+			 * filters look as good on low-res textures as on high-res ones, by making
+			 * low-res textures BECOME high-res ones.  This is helpful for worlds that
+			 * mix high- and low-res textures, or for mods with least-common-denominator
+			 * textures that don't have the resources to offer high-res alternatives.
+			 */
+			const bool filter = m_setting_trilinear_filter || m_setting_bilinear_filter;
+			const s32 scaleto = filter ? g_settings->getU16("texture_min_size") : 1;
+			if (scaleto > 1) {
+				const core::dimension2d<u32> dim = baseimg->getDimension();
+
+				/* Calculate scaling needed to make the shortest texture dimension
+				 * equal to the target minimum.  If e.g. this is a vertical frames
+				 * animation, the short dimension will be the real size.
+				 */
+				if (dim.Width == 0 || dim.Height == 0) {
+					errorstream << "generateImagePart(): Illegal 0 dimension "
+						<< "for part_of_name=\""<< part_of_name
+						<< "\", cancelling." << std::endl;
+					return false;
+				}
+				u32 xscale = scaleto / dim.Width;
+				u32 yscale = scaleto / dim.Height;
+				const s32 scale = std::max(xscale, yscale);
+
+				// Never downscale; only scale up by 2x or more.
+				if (scale > 1) {
+					u32 w = scale * dim.Width;
+					u32 h = scale * dim.Height;
+					const core::dimension2d<u32> newdim(w, h);
+					video::IImage *newimg = driver->createImage(
+							baseimg->getColorFormat(), newdim);
+					baseimg->copyToScaling(newimg);
+					baseimg->drop();
+					baseimg = newimg;
+				}
+			}
 		}
 		/*
 			[resize:WxH

src/client/wieldmesh.cpp

@@ -297,8 +297,11 @@ void WieldMeshSceneNode::setExtruded(const std::string &imagename,
 		material.MaterialType = m_material_type;
 		material.MaterialTypeParam = 0.5f;
 		material.BackfaceCulling = true;
+		// Enable bi/trilinear filtering only for high resolution textures
+		bool bilinear_filter = dim.Width > 32 && m_bilinear_filter;
+		bool trilinear_filter = dim.Width > 32 && m_trilinear_filter;
 		material.forEachTexture([=] (auto &tex) {
-			setMaterialFilters(tex, m_bilinear_filter, m_trilinear_filter,
+			setMaterialFilters(tex, bilinear_filter, trilinear_filter,
 					m_anisotropic_filter);
 		});
 		// mipmaps cause "thin black line" artifacts