Own the context — Parallax Sketchbook

SKETCHBOOK / 01 The platform bench · 2-week chapter

Page 1 of 3: The observatory starts with a context

A new project, one visible result

The observatory starts with a context

Chromatic Observatory is a small interactive exhibit: colored panels become a room of textured, lit objects, then a multipass scene with shadows. You will build it in stages over sixteen weeks. The supplied native starter draws one rotating colored triangle and includes a separate --camera checkpoint with three overlapping exhibits, real model/view/projection uniforms, depth testing and a resizable orbit view. The textured room, lighting and later multipass systems are your progressive extensions.

OpenGL commands operate through a current context. GLFW creates the window and context, handles events, and presents a buffer. GLEW loads the entry points used by the program after the context becomes current. These roles are separate: a successful C++ build neither proves context creation nor guarantees that a requested driver feature exists.

The primary target is your AMD machine on CachyOS. Start with OpenGL 3.3 core and GLSL 330 so the course has one explicit baseline. Record the actual vendor, renderer, and version on that machine. A newer driver can expose more features, but the first working triangle should not depend on them.

TRY IT IN YOUR STUDIO

Build the separate native project. Record actual driver strings, command and result. If context creation fails, preserve the diagnostic before changing dependencies.

LOOK CLOSER

cmake -S native/advanced/opengl -B build-observatory -G Ninja \
  -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_BUILD_TYPE=Debug
cmake --build build-observatory --parallel
ctest --test-dir build-observatory --output-on-failure
./build-observatory/observatory --smoke

Repository-root commands. CMake discovers an existing GLFW, GLEW and OpenGL development environment; it does not install dependencies.

From the page to your own work

Your studio assignment.

Open the observatory without hiding its lifetime rules.

A finish line you can see

Your own clear-color variation, driver report, and destruction diagram.

Build and run the starter on your target machine.
Change the background and verify resize/minimize behavior.
Explain an ordinary failure and show GPU owners ending before the context.

Keep the evidence in your weekly notebook ↗

Explain it like an engineer

Try answering aloud before opening the review notes. Use your own implementation as evidence.

What does RAII fail to prove about an OpenGL resource?

It establishes a deletion responsibility, not the current context.
The context and submission thread must remain valid.
Queued work and cross-context sharing require additional contracts.

These prompts support practice; they are not an automatic assessment of your work.

A tip for this exercise

Keep your first change visible and small: one background color. Save the driver report before editing, so you can distinguish a successful build from a working context on this machine.

Hints, when you need them.

Try a first step, then reveal as much help as you need. Each hint gets a little more specific.

1Hint 1 · Find a starting point

Draw the window, context, and resource owners as nested boxes. Which box must still exist when a buffer owner is destroyed?

2Hint 2 · Choose an approach

Follow setup in order: create the window, make its context current, load functions, then create resources. Trace cleanup backward through those boundaries.

3Hint 3 · Check your reasoning

Your checkpoint is a changed background that survives resize and minimize, plus a diagram placing GPU cleanup before window destruction and GLFW termination.

A small creative variation ↗

Change the window title and one palette value; keep the lifetime structure fixed.

Optional. Save it for later if this chapter already feels full.

Coming back after a break? ↩

Run the last known-good smoke command and read one driver line before editing.

Books & principles behind this study +

Original Parallax explanations and assignments, with these works for further reading.

YOUR MARGIN NOTES

Leave yourself a good question.

What changed your mind? What would you try next?

Notes for Own the context

Notes are private to this browser and saved as you write.

A CHECKPOINT, NOT A SCORE

Can you explain the idea and try the exercise yourself?

Completion records your own assessment. It does not compile or test your C++.

Companion source 3 files