Post-processing

OkPostProcess is the engine's post-process chain. With render.post enabled, the whole world pass renders into an offscreen framebuffer (a colour texture plus a depth texture) instead of the window, and a final full-screen pass composites it to the window applying the enabled effects. With render.post off the chain vanishes: the engine renders directly to the window exactly as before, at zero cost.

The GUI and camera-attached passes draw after the composite, directly to the window — the interface stays sharp and grain-free. (The design leaves room for a later per-stage GUI chain with its own effect intensities, e.g. a HUD that motion-blurs less than the world.)

Effects

All in one composite shader, each gated by its config toggle:

• Depth of field (post.dof) — diorama-style: fragments inside the focus band (the focus distance ± post.dof.range, metres) stay sharp; blur grows with distance from the band up to post.dof.maxblur pixels (8-tap ring blur over the linearized depth buffer).
• Film grain (post.grain) — animated per-pixel hash noise, post.grain.strength in colour units. Also hides procedural repetition and banding.
• Bloom (post.bloom) — the frame's bright areas are extracted above post.bloom.threshold (with a soft shoulder set by post.bloom.knee), blurred separably at half resolution and added back with post.bloom.strength. Because it works on the finished frame rather than on the objects, the cost is the same whether one surface glows or ten thousand do, which is what makes it the affordable way to sell emissive surfaces as sources of light. A surface that should glow needs to be driven past white, so it clears the threshold.
• Directional motion blur (post.motionblur) — screen-space smear along a game-supplied velocity vector: OkPostProcess::setMotionVector(dx, dy, strength) each frame (e.g. from vehicle speed); strength 0 disables it. Samples 7 taps along the vector.

Configuration keys

Autofocus

With post.dof.autofocus on (the default), the focus distance follows whatever is under the middle of the screen instead of sitting at post.dof.focus. A fixed distance only suits a camera that stays a fixed distance from its subject; as soon as the viewpoint can climb, everything is far away and the whole frame falls out of focus.

The depth of a single pixel is read back through a pixel buffer object and collected on the next frame, so the CPU never waits on the GPU — one frame of lag is invisible, a stall is not. The result is eased rather than applied outright, because a hard cut as the camera sweeps past a near wall reads as a glitch while a real lens takes a moment to find its subject. Sky (nothing at that pixel) leaves the focus where it was.

Choosing the numbers

Two defaults are set wide on purpose, and both for the same reason: a viewpoint that can climb.

The sharp band and falloff are generous because the focus distance is fixed. A tight band suits a camera a few metres from its subject, but once the viewpoint rises, everything on screen is hundreds of metres away and a tight band blurs the whole frame.

The bloom threshold is high enough that only actual light sources glow — lit windows, lamps, a sun disc. A daytime sky is bright over most of its area, so a low threshold sends the entire sky through the blur and washes the top half of the screen to white. At night nothing but the lights passes either threshold, so raising it costs nothing there.

Everything is console-reachable (set post.dof.focus 25, set render.post false).

Integration

OkCore calls begin(fbWidth, fbHeight) before clearing the frame (binds the offscreen target, recreating it lazily on resize) and end(near, far, dt) after the scene — the near/far planes of the current camera linearize the depth buffer for the DoF. The offscreen target follows the real framebuffer size, so HiDPI displays keep their native resolution. The composite draws a bufferless full-screen triangle (gl_VertexID trick), so the pass costs one draw call.