Orklev2 Scenegraph

Orkid Scene Graph Rendering Reference

When answering questions about scene graphs, 3D rendering, cameras, or lighting in orkid, consult these files. All under ork.lev2/.

Key Files

Implementations: src/gfx/scenegraph/, src/gfx/camera/, src/gfx/lighting/

Hierarchy

Scene
├── Layer (named, sorted by _sortkey)
│   ├── DrawableNode (holds Drawable)
│   ├── LightNode (holds Light)
│   └── ProbeNode (holds LightProbe)
└── LightManager, CompositingData, CameraDataLut

Scene Creation (Python)

params = core.VarMap()
params.preset = "ForwardPBR"
params.SkyboxTexPathStr = "nebula"
params.clearcolor = fvec3(0.1, 0.1, 0.5)

scene = lev2.scenegraph.Scene(params)
layer = scene.createLayer("std_forward")

Drawable Types

# Model
model_data = lev2.ModelDrawableData("data://tests/testcube.glb")
drawable = model_data.createDrawable()
node = layer.createDrawableNode("cube", drawable)
node.worldTransform = matrix
node.modcolor = fvec4(1, 1, 1, 1)
node.enabled = True

# Instanced
inst_data = lev2.InstancedModelDrawableData("data://models/sphere.glb")
inst_data.resize(1000)
inst_drawable = inst_data.createDrawable()
node = layer.createDrawableNode("spheres", inst_drawable)

Camera Setup

# CameraData
cam = lev2.CameraData()
cam.Lookat(eye=fvec3(0,3,8), tgt=fvec3(0,0,0), up=fvec3(0,1,0))
cam.Persp(near=0.1, far=1000.0, fov_degrees=45.0)

# CameraDataLut (named camera registry)
camera_lut = lev2.CameraDataLut()
camera_lut.create("main_cam")

# EzUiCam (interactive mouse camera)
from lev2utils.cameras import setupUiCameraX
cam_data, ui_cam = setupUiCameraX(
    cameralut=camera_lut, camname="main_cam",
    eye=fvec3(0,3,8), tgt=fvec3(0,0,0), up=fvec3(0,1,0), far=1000.0)

# Camera event handler
def on_cam_event(ev):
    handled = ui_cam.uiEventHandler(ev)
    if handled:
        ui_cam.updateMatrices()
        cam_data.copyFrom(ui_cam.cameradata)
    return lev2.ui.HandlerResult()

Lighting

# Point Light
light_data = lev2.PointLightData()
light_data.mColor = fvec3(1, 1, 1)
light_data._intensity = 1.0
light_data.mbShadowCaster = True
light = light_data.createDrawable()
light_node = layer.createLightNode("main_light", light)
light_node.setMatrix(transform_matrix)

# Directional Light
dir_data = lev2.DirectionalLightData()
dir_data.mColor = fvec3(1, 0.9, 0.8)
dir_data._intensity = 0.5

# Spot Light
spot_data = lev2.SpotLightData()
spot_data.mFovy = 45.0  # Cone angle degrees
spot_data.mRange = 50.0

Light types: ELIGHTTYPE_POINT, ELIGHTTYPE_DIRECTIONAL, ELIGHTTYPE_SPOT, ELIGHTTYPE_AMBIENT

SceneGraphViewport Widget

# Create viewport in layout
item = layout_group.makeChild(
    uiclass=lev2.ui.SceneGraphViewport, args=["viewport"])
sgvp = item.widget

sgvp.scenegraph = scene
sgvp.cameraName = "main_cam"
sgvp.camera_evhandler = on_cam_event
sgvp.forkDB()  # Required for embedded viewports

# GPU update all viewports (call in render loop)
lev2.ui.SceneGraphViewport.gpuUpdateAll(context)

Layer Conventions (PBR2 Phase 0)

The forward pipeline knows these layer roles (fwdnode_impl_top.cpp:k_roles[]):

The probe cubemap CPD calls assignLayers(probe->renderLayer()) as a hard reset — only that one layer renders during a probe capture. Place HUD/debug content on hud_overlay, editor gizmos on std_editor, so neither appears in reflection probes.

Probe Nodes Register With LightManager

Layer::createProbeNode(name, probe) adds the probe to LightManager._lightprobes, making it discoverable via LightManager::findProbeByName(name). Non-lighting subsystems (e.g. ECS ParticlesGlobalSystem) resolve probes by entity name at _onActivateComponent time and cache the resolved lightprobe_ptr_t on the drawable (Drawable::_probeOverride) for per-draw cubemap selection.

Render Loop

# In onUpdate:
scene.updateScene(camera_lut)

# In GPU render:
scene.renderOnContext(context)

Node Properties

node.worldTransform = fmtx4()   # World matrix
node.modcolor = fvec4(1,1,1,1)  # Color modulation
node.enabled = True              # Visibility
node.pickable = True             # Picking support
node.view_relative = False       # View-space transform

Thread Safety

Scene graph uses LockedResource<T> for all collections:

# Python access returns copies (thread-safe)
nodes = layer.drawable_nodes
layers = scene.layers

How to Answer

1. For scene setup: read scenegraph.h and pyext_gfx_scenegraph.cpp
2. For drawables: read drawable.h for all DrawableData types
3. For cameras: read cameradata.h and uicam.h for EzUiCam
4. For lighting: read gfx_lighting.h for all light types
5. For examples: check ork.lev2/pyext/tests/ui/sgui_emb_sg.py

Source: tweakoz/orkid — distributed by TomeVault.