mesh.md

3D geometry atom in prysm

renders a particle that is a 3D scene. a leaf in the element tree (leaf type: mesh). the rendering pipeline is entirely separate from the 2D compositor — mesh requires a GPU mesh pipeline with depth buffer, PBR materials, and a lighting model. the primary format is glTF

for raster images see prysm/image. for 2D paths see prysm/vector

protocol role

mesh is a leaf in the element tree $\mathcal{T}$ (§7 of prysm/layout). leaf type: mesh. it has no sub-organelles. its membrane constrains the 2D viewport into which the 3D scene is projected. the scene itself is infinite

glTF structure

a glTF particle delivers:

scene graph — hierarchical node transforms
meshes — vertex buffers, index buffers, primitive topology
materials — PBR (metallic/roughness), base color, normal map, emissive
textures — embedded raster maps for material channels
skeleton — bones and bind poses for skinned meshes
animations — keyframe tracks (translation, rotation, scale, morph weights)
lights — point, spot, directional (glTF extension)
cameras — perspective and orthographic views

sizing

all values in spatial quanta $g$

parameter	sizing type	values	default
src	—	particle CID	required
width	fix or fill	any $k \cdot g$ or fill	fill
height	fix or fill	any $k \cdot g$ or fill	fill
camera	—	scene default or override	scene default
background	—	transparent or color	transparent

$s_{min} = (8g, 8g)$

camera and interaction

the default camera comes from the glTF scene. if no camera is defined, a perspective camera is placed at $(0, 0, 5)$ looking at origin. the membrane can expose orbit interaction (drag to rotate, scroll to zoom) — this is a property of the membrane, not the mesh atom

animations

if the glTF contains animation tracks, mesh exposes an AnimationState:

state	behavior
idle	first frame of default animation
playing	advancing animation clock
paused	animation clock stopped

animation playback is driven at the molecule/cell level — mesh atom exposes the clock

states

state	visual change	trigger
default	rendered at current animation frame	src loaded
loading	glass placeholder, pulse $1\text{s}$	src not yet resolved
error	vector [broken-mesh, $4g$, anger]	src failed

state transitions: $150\text{ms}$ ease

emotion

mesh carries emotion as an emissive overlay — a color tint added to the material's emissive channel at 12% intensity. this is equivalent to the 12% glass tint on image and glass atoms, adapted to 3D surface shading

3D

mesh is natively 3D. in the prysm 3D extension:

mesh renders into its own render pass with full depth buffer
the membrane defines the 2D viewport rect into which the projection is composited
mesh does not billboard — it has its own orientation from the scene graph
scale from $g$ quanta applies to the viewport size, not the internal 3D scale

ECS

Entity: mesh organelle
Components:
- Sizing { width, height }
- MeshSrc { cid } — glTF particle CID
- MeshCamera { scene_default | Override(transform) }
- MeshBackground { transparent | Color }
- AnimationState { idle | playing | paused }
- AnimationClock { f32 } — seconds
- LoadState { loading | loaded | error }
- EmissiveTint { emotion: Option<Color> } — 12% emissive overlay
System: MeshSystem drives render pass, advances animation clock, composites into 2D layout

Homonyms

prysm/mesh

cyb/evy/forks/bevy_render/src/mesh

mesh