9. album od Maxmiliána Šumbery s názvem Letní imprese je nově k dispozici na Audiomack. Skladby Duo pro hoboj a klavír No.1 “Ametystové červánky” a Rozkvetlé louky se umístily ve zlátém pásmu soutěže XIII. Múzy I.Hurníka 2025. Navíc první z nich dostala také zvláštní cenu v kategorii instrumentální hudby.
Disclosure: AI-assisted content — consult with an organic-developer.
When building low-level libraries for the JVM — especially those that interact with JNI, rendering engines, or MethodHandles — the exact bytecode emitted matters. Recently I hit a limitation in Kotlin that reminded me why the JVM world still needs Java for certain things.
Here are the main areas where Kotlin’s generated bytecode diverges from Java’s, and why that matters.
| Area | Java | Kotlin | Takeaway |
|---|---|---|---|
| Signature-polymorphic calls | Emits correct signature for MethodHandle.invokeExact | Falls back to (Object[])Object, causing mismatches | Keep these calls in Java |
| Default parameters | No defaults → use overloads | Generates synthetic $default methods with bitmask | Avoid defaults in public APIs for Java clients |
| Companion objects / @JvmStatic | True static methods | Methods live in $Companion unless annotated | Use @JvmStatic or plain Java for static APIs |
| Internal visibility | Package-private supported | internal compiles to public + metadata | Don’t rely on internal for cross-language encapsulation |
| SAM interfaces | Any functional interface = lambda | Only fun interface supports SAM; lambdas may create synthetic classes | Define callbacks in Java for performance |
| Nullability | All references nullable | Annotations encode nullability, JVM doesn’t enforce | Explicit null checks needed in low-level code |
| Suspend functions / coroutines | N/A | Compiles to (Arg, Continuation) → Object | Keep coroutines in Kotlin wrappers, not core API |
This wasn’t an isolated issue. Kotlin differs from Java in other ways that make it risky for core interop code:
| Area | Java | Kotlin limitation |
|---|---|---|
| JNI declarations | static native boolean render(int, int) | Needs @JvmStatic in a companion object; generates synthetic names |
| JNI header generation | javac -h works directly | No header generation for Kotlin sources |
| Checked exceptions | Enforced at compile-time | Kotlin ignores them (all unchecked) |
| Raw types | Allowed (List) | Always requires generics (List<*>) |
| Wildcards | ? super, ? extends supported | Only in / out; cannot express everything |
| Default params | Not supported (overloads instead) | Compiles to synthetic $default methods |
| Static members | static keyword | Requires @JvmStatic in object/companion |
| Suspend functions | N/A | Compiled to Continuation-based state machines, awkward for Java callers |
A low-level library often deals with:
MethodHandlesAll of these require predictable bytecode and signatures. Kotlin often inserts synthetic classes ($Companion, $DefaultImpls, $WhenMappings) or adapts signatures in ways Java clients (and JNI) do not expect.
| Benefit | Why It Matters |
|---|---|
| One language to maintain | Single codebase, easier contributor onboarding, faster builds |
| Interop for everyone | Java APIs work in all JVM languages; Kotlin clients lose nothing; Java clients stay safe from Kotlin-only features |
| JNI friendliness | Direct mapping of Java types to JNI (int → jint, boolean → jboolean); javac -h header generation works; avoids $Companion/$DefaultImpls surprises |
| Bytecode predictability | No synthetic baggage ($Companion, $default, $WhenMappings); avoids mismatched signatures; JIT optimizes exactly as written |
The pattern I adopted (and which many frameworks use):
MethodHandle, VarHandle, Unsafe-ktx)
suspend wrappers)This is the same model Android Jetpack follows:androidx.core in Java, androidx.core-ktx in Kotlin.
| Point | Why |
|---|---|
| MethodHandle support | Java compiler emits exact signatures ((int,int)boolean), Kotlin falls back to (Object[])Object, causing runtime issues |
| Bytecode predictability | Java produces direct, predictable bytecode; Kotlin adds synthetic constructs and indirections |
| JNI compatibility | Java maps directly to JNI types and header generation; Kotlin introduces complications |
| Best practice | Keep the core in Java for stability and performance; add Kotlin wrappers for ergonomics (DSLs, coroutines, null-safety) |
interesting link: https://www.okoone.com/spark/technology-innovation/why-kotlin-swift-and-ruby-are-dropping-off-the-radar/
MethodHandle and signature-polymorphic methodsinternal, etc.)Po skoro 30 letech od ‘obyčejné’ klavírní verze je tu verze orchestrální. Překvapivě bohatá a rozšiřující původní námět. Zvláště střední a závěrečná, epicky znějící část, se mi velmi líbí. Orchestraci z původní skladby vytvořil a vhodně rozšířil Maxmilián Šumbera.
Night runner, my favourite one released ! I love the uncommon accents forming a distinct rhythm, interleaving with a faster pulse — like a heartbeat echoing the rhythm of feet hitting the ground in that first minute.
Realita vs. iKatastr 3d. Vizuální srovnání pomocí fotek z terénu.
porovnání u prototypu zde
This is another nice half-frame camera — the Olympus PEN-D. It has an uncoupled meter and a smart way of setting aperture and shutter speed together. Works great and produces nice photos. Compared to the Canon Demi EE28 , it’s a bit bulkier, mostly due to the faster Zuiko 1.9 lens.
It features a Copal leaf shutter, fully mechanical, so no batteries are needed. Focusing is manual via a distance scale. Zone focusing works well once you get a feel for it.
Shutter speeds range from 8s to 1/500s.
I gave a presentation where GIS might evolve in 20 years from now as part of the GIS Ostrava 2025 conference on 5.3. 2025. it was great to see again colleagues ! get eye-contact with audience and not just virtual applause. Also nobody was showing physically thumbs-up or red heart (in that case I would call emergency), rather real spoken (I mean real sound wave based ) comments, real talk and smiles. That was the main topic of the talk – Spatial Interactive – with people, tech, discoveries. Step out of the ‘glass-illusion’ trap.
Stanislav Sumbera, GIS Vision 2024, 5.3. 2025,GIS Ostrava 2025
image sources:https://gislab.utk.edu/tag/ar-sandbox/ , Dyamicland.org, Lightform
from Book: Eneterpise SOA by Krafzig, Banke, Slama
Image from Jumanji 2,driver – Mason Pike ?
from page 16 of the great book uncommon sense, common nonsense. by Jules Goddard and Tony Eccles.
2 quotes form czech book on Bata system :
Taylor, Fayol, Ford, and Baťa put an end to the old type of entrepreneur for good. They argued that profit does not depend on the numerically lowest wages, but on the highest and most efficient work performance, during which the worker works as if he were working for himself.
“Baťa’s factories produced and supplied most of the construction materials themselves. They had their own brickyards, carpentry, joinery, and locksmith workshops, which supplied standardized interior fittings to all homes, produced neon tubes, flooring, in short, almost everything they needed. And if there was something not included in their production program, they purchased it directly from manufacturers (excluding intermediaries).”
Novinky
24.7.’25 Podívejte se na zajimavé srovnání reality na fotce (kinofilm) s virtuálním pohledem do stejného místa v iKatastr 3d.
20.6.’25: Nová 3D verze, obsahuje reliéf terénu, výškové obrysy budov a využívá akceleraci grafické karty. Vyzkoušejte v testovacím provozu https://ikatastr.cz/3d
23.2.’25: zlepšeno rozlišení základních map pro ‘retina’ obrazovky. Oprava drobných chyb.
17.2.’25 aktualizována mapová komponenta Leaflet na poslední verzi 1.9.4.
27.1.’25: Přidána vrstva označující nemovitosti, které obsahují cenový údaj v katastru nemovitostí. Vyzkoušejte např zde. Ovšem sdělení konkrétní ceny je pouze na vyžádání na katastru. Viz ceník zde, položka 4021 a 4022.
13.1.’25: Export 1000 parcel do CSV souboru (test rychlosti procházení záznamy a exportu): https://www.youtube.com/watch?v=frBXLgSkHgU
2.1.’25 : Přidána možnost exportu parcel do csv souboru.
18.12. Přidány vrstvy zasíťování (voda, elektřina, plyn, kanalizace, apod). vyzkoušejte zde.
A také vrstvy leteckých snímků z minulých let, které můžete jednoduše procházet –video zde.
Nová videa pro náročné: iKatastr.cz na Apple Vision Pro a Test 3D prototypu na Apple Vision Pro
We have various terms for AR – like Mixed Reality, Metaverse, Spatial-ware, XR. Among these, Apple’s term “Spatial Computing” stands out for its emphasis on integrating physical space and digital interactivity. This resonates with me, as the concept of “Spatial” reflects how we model and interact with space in meaningful ways. Years ago, I made up a new term “SpatialIn”—an open-ended label where “In” simply means Spatial is “in.” Later, with advancements like ARKit, I extended this idea into “Spatial Interactive,” emphasizing the interactive potential of space around us behaving like a dynamic canvas. Vision Pro aligns perfectly with this vision. After testing Vision Pro , here are my key observations:
Vision Pro’s hands-free interaction feels intuitive. Manipulating virtual objects with gestures or gaze eliminates barriers and enhances usability. Fluent hand movements remind me of my Tai-Chi classes from years ago.
Unlike VR, Vision Pro allows safer navigation in real spaces while engaging with virtual elements. It maintains spatial awareness and visual contact with reality, making it both practical and immersive.
Vision Pro’s capability to retain virtual object placement across sessions is impressive. This feature is critical for practical applications such as architectural design, where models need to stay precisely where placed for accurate spatial referencing, or in education, where persistent virtual setups can create consistent and engaging learning environments. I found a model I placed earlier in the day still standing on the lower floor of the building—exactly where I left it. This happens without explicit relocalization notification for the user, as the virtual model sticks to the physical space even across different floors. A must for advanced spatial computing design as virtual space must keep integrity similar to physical one.
The wide field of view and detailed lighting ensure a natural integration of digital and physical environments. Soft shadows and consistency make virtual elements feel tangible. Fidelity is so high that it creates the illusion of tactile sensation when interacting with virtual models. While purely subjective, this visual illusion convincingly engages my sense of touch, making the experience feel remarkably real to me. This visual-feel integration adds a layer of immersion that goes beyond sight and sound, engaging the sense of presence in a way that feels almost instinctive.
Here is a little example – while using only flat browser with WebGL powered MapLibreGL there: Update 07/2025 -live version here, e.g. : https://ikatastr.cz/3d/#kde=50.741216,15.001038,15.4,50,75&mapa=letecka&vrstvy=budovy3d,peaks,zsj,ku,obce,parcelybudovy&info=50.732718,14.984554
As there is no 3D map from Apple to test on the device by default, I had to convert a gltf to USDZ and send it to device for QuickLook to get experience of how 3D city would look like there.Here it goes: