Deki Rendering

Docs: https://dekiengine.github.io/deki-rendering/ (components and properties, generated from the code)

Core rendering pipeline for the Deki Engine: camera, render system, standard 2D renderer, render passes, and sorting callbacks.

Part of Deki Engine.

Namespace

Types live in DekiRendering. Scene files store the qualified name, and so does code:

using namespace DekiRendering;
obj->AddComponent<SomeComponent>();

Install

Package Manager in the Deki Editor, or DekiEditor --packages-add deki-rendering <project>.

Camera

CameraComponent decides how much world the player sees. Orthographic, it shows orthoHeight meters top to bottom and the width follows the screen: a bigger screen of the same shape shows the same world drawn bigger, a wider one shows more at the sides. Perspective, it shows a vertical fieldOfView for 3D meshes. pixelPerfect scales by whole numbers for pixel art. Every screen renders at its own resolution.

Partial present (dirty rectangles)

Off by default. Turn on the project's Rendering setting dirtyTileTracking and the render system tracks what each frame actually touched:

• It records every rectangle drawn. QuadBlit reports each clipped blit; a pass writing the framebuffer directly calls QuadBlit::MarkDirty.
• It clears only last frame's rectangles instead of the whole framebuffer.
• It sends the display this frame's and last frame's rectangles, aligned to dirtyTileSize, through Deki::IDisplay::PresentRegions.

Displays that cannot do partial frames keep getting whole ones. Double buffering works: history is kept per buffer pointer. A first frame, a resize, a clear-colour change, a swapped display or DekiRendering::DekiRenderSystem::MarkAllDirty() fall back to a full clear and a full present.

Editor and SDL3 displays present partial frames. The LovyanGFX display's partial present (row bands through a small DMA staging buffer, which also stops the byte swap for big-endian panels from mutating the engine's framebuffer) runs on hardware, on the LilyGO T-Deck Plus.

Whole frames or strips (frameMode)

The Rendering setting frameMode says how each frame reaches the screen on a device. Leave it at Auto: when the game starts, it picks whole frames if the framebuffer fits in internal RAM with 64 KB to spare for the game, and strips if not. A display that cannot take part of a frame always gets whole frames. The editor always draws whole frames.

	Whole frames	Strips
How	Each frame drawn once into one framebuffer, then sent while the next is drawn	Each frame drawn a strip of bandRows rows at a time into a small buffer in internal RAM, each strip sent while the next is drawn
Faster when	The framebuffer fits in internal RAM	It does not, so it would live in PSRAM, where every blend is several times slower
Measured (ESP32-S3)	T-Deck Plus, 320x240, 150 KB: 61 fps in the demo's effects scene against 59 in strips	T-Display S3 AMOLED, 536x240, 251 KB: 61 fps against 22 drawing whole frames in PSRAM
Internal RAM	The framebuffer	A strip and two copies of it for sending: 126 KB at 536x240 and 40 rows

Both give the same pixels. The boot log says which a board uses and why, for example [Rendering] whole frames: the 150 KB framebuffer fits in internal RAM (259 KB free), and DEKI:STATS (the editor's device_stats) reports it as frameMode=whole or frameMode=strips bandRows=40. Choose WholeFrames or Strips only to override that, to measure both, say.

Strips

There is no framebuffer in strips, which is the point when a whole one only fits in PSRAM. Strips keep every feature whole frames have:

• Dirty rectangles: every strip is still drawn, but only the rows this frame or the last drew in are sent, and a strip with none is not sent. The strip buffer is cleared only where the strip drawn before it drew.
• A camera with clearEveryFrame off: the frame is kept in PSRAM, and each strip is read from it before drawing and written back after. The first frame the camera stops clearing starts from the clear colour.
• Screenshots: DekiRenderSystem::RequestFrameCapture() copies the next frame's strips into a PSRAM frame, which GetFrameBuffer() returns until the frame after. The device's DEKI:SCREENSHOT asks for one.
• A renderer or pass that cannot draw in strips (DrawsInStrips(), false by default for a renderer and for a pass with BeginFrame or EndFrame; the 3D mesh pass while the scene has a mesh) gets whole frames, drawn in PSRAM, for as long as it cannot, and the log says so.

Dependencies

Dependency	Type
deki-editor	Deki editor DLL

License

Apache 2.0. See LICENSE.