Effects and game feel

Add transient effects as short-lived, self-owning entities triggered by application events, not as permanent scene fixtures.

Reuse before authoring. Adapt the closest official particle example with

find-examples

, prefer the Engine's built-in particle component over a hand-written system, and discover any shipped trail or effect script with

reuse-scripts

Copy particle curve construction from the installed example exactly.

CurveSet

takes one key array per channel, such as

new CurveSet([0, x0, 1, x1], [0, y0, 1, y1], [0, z0, 1, z1])

; do not flatten three channels into one array. A malformed curve can type-check and then fail inside the particle texture upload. Create one emitter, render a frame, and require empty runtime and console diagnostics before reusing the helper for smoke, spray, or splashes.

For a polished wake, smoke, or spray requirement, do not stop at scaled planes, crossed billboards, or generic render primitives. Use the built-in particle component for smoke and spray; reserve a custom mesh and material for a continuously sampled wake ribbon. Verify tint and blending against the actual scene lighting and surface.

Place and layer

Spawn an effect at the emitter's world mount point, either parent it there or copy the world transform once, and let it destroy itself when finished. Never leak emitters.
Keep additive or transparent effects above the surface they sit on and biased toward the camera so they do not z-fight. Inspect soft transparency at grazing angles for hard edges, black quads, or dropout.
Size and orient effects from the emitter's calibrated bounds, not a guessed constant.

Moving trails

Treat built-in render primitives as blocking geometry for soft effects. Follow the closest official example to choose particles, a custom mesh, textures, materials, and blending for the intended visual behavior.
Match every custom mesh's vertex streams to its material. A lit
```
StandardMaterial
```
needs normals; calculate and set them before
```
mesh.update()
```
, or deliberately use an unlit material. Treat a missing vertex-attribute diagnostic as a rendering failure even when some frames still appear. For a dynamic horizontal ribbon created with
```
setVertexStream
```
, allocate a normal array alongside positions, fill every vertex with
```
(0, 1, 0)
```
, and upload it as
```
SEMANTIC_NORMAL
```
before the first
```
update()
```
. Recheck this whenever changing the ribbon's material type.
Never attach an empty dynamic mesh to an enabled render component. Upload a valid initial vertex and index set before creating its
```
MeshInstance
```
, or keep the render entity disabled until the first complete update. On reset, disable it or restore valid seed geometry; do not call
```
mesh.clear()
```
while an enabled renderer still references it. Reflection and refraction cameras render the same mesh and can expose this lifecycle bug before the gameplay camera does.
Judge a trail from its intended cameras. If it reads as a flat decal, use the reference example to add the minimum depth cue needed rather than stacking arbitrary geometry.
Sample the trail continuously. Append segments on a small time- or distance-step and interpolate between them; coarse per-distance chunks make the trail stutter and break into visible dashes as the object speeds up.
Anchor it to the mover's contact or exhaust point, scale emission rate and length with speed, and fade the tail so it dissolves instead of cutting off with a hard edge.

Camera shake and hit feedback

Drive camera shake as a decaying offset on a camera parent or an additive layer; never write it into the smoothed chase position, or it fights the follow. Keep shake and follow separate, as the orbit-camera rule in
```
apply-conventions
```
requires.
Stagger the parts of a compound effect over a few frames — flash, then smoke, then splash — so an event reads as a sequence rather than a single pop.
Keep the readable peak long enough for the gameplay camera to see the layers together. A flash can be brief, but the longer-lived layers should overlap for several frames rather than leaving the primary action frame visually identical to the idle state.
For side-mounted emitters, derive every spawn point and direction from calibrated world-space mounts on the mover. Confirm the effect starts outside the source geometry from both sides; an active cooldown with only a tiny flash elsewhere in the frame is failed feedback.

Prove it fires

Trigger each effect through real gameplay input and confirm with a screenshot captured at its peak, not a saved filepath. Confirm the effect is visible from the gameplay camera and from a grazing angle, that emitters are gone after their lifetime (query the entity count), and that nothing leaves a black quad or a hard edge over the surface.

Choose the authoring surface with the

build-app

skill; create effects through its entity and component primitives and own their lifecycle in the surface that spawned them.

add-effects

NPX Install

Tags

SKILL.md Content

Effects and game feel

Place and layer

Moving trails

Camera shake and hit feedback

Prove it fires