Improve shadow filters (#12195)

* Rewrite shadow filtering for the new distortion
* Calculate penumbra radius using a single sample
* Avoid peter-panning effect due to filtering of short shadows
* Add adaptive filter quality for soft shadows
* Avoid sharp shadows on surfaces without normals (e.g. plants)
* Increase default and maximum soft shadow radius
* Make line numbers in shader errors match the code

src/client/clientmap.cpp

@@ -489,6 +489,8 @@ void ClientMap::renderMap(video::IVideoDriver* driver, s32 pass)
 				// Do not enable filter on shadow texture to avoid visual artifacts
 				// with colored shadows.
 				// Filtering is done in shader code anyway
+				layer.BilinearFilter = false;
+				layer.AnisotropicFilter = false;
 				layer.TrilinearFilter = false;
 			}
 			driver->setMaterial(material);

src/client/shader.cpp

@@ -771,6 +771,8 @@ ShaderInfo ShaderSource::generateShader(const std::string &name,
 		shaders_header << "#define SOFTSHADOWRADIUS " << shadow_soft_radius << "\n";
 	}
 
+	shaders_header << "#line 0\n"; // reset the line counter for meaningful diagnostics
+
 	std::string common_header = shaders_header.str();
 
 	std::string vertex_shader = m_sourcecache.getOrLoad(name, "opengl_vertex.glsl");

src/client/shadows/dynamicshadowsrender.cpp

@@ -670,6 +670,7 @@ std::string ShadowRenderer::readShaderFile(const std::string &path)
 	std::string prefix;
 	if (m_shadow_map_colored)
 		prefix.append("#define COLORED_SHADOWS 1\n");
+	prefix.append("#line 0\n");
 
 	std::string content;
 	fs::ReadFile(path, content);

src/defaultsettings.cpp

@@ -274,7 +274,7 @@ void set_default_settings()
 	settings->setDefault("shadow_filters", "1");
 	settings->setDefault("shadow_poisson_filter", "true");
 	settings->setDefault("shadow_update_frames", "8");
-	settings->setDefault("shadow_soft_radius", "1.0");
+	settings->setDefault("shadow_soft_radius", "5.0");
 	settings->setDefault("shadow_sky_body_orbit_tilt", "0.0");
 
 	// Input