Effects and game feel

Trigger transient effects through application events and reuse their resources.

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

• Place an effect at the emitter's world mount point; parent it there or copy the world transform once.
• 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.

Pool and prewarm

• Create emitters, ribbons, flashes, materials, and meshes at load. Events check out an effect, set its transform, and call particlesystem.reset() then play(); after its particles finish, call stop() and return it to the pool.
• First-use shader compilation can stall a frame. Before gameplay, render every material and particle variant through the relevant passes, on an offscreen rig or behind the ready overlay.
• Pulse or tint uniforms with meshInstance.setParameter or material.setParameter. material.update() marks the whole material dirty and clears variants when defines or chunks change; reserve it for material changes that require it.

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 repeated events leave entity counts stable, and that nothing leaves a black quad or a hard edge over the surface. Compare graphicsDevice.shaders.length after prewarming and after the first real event; growth indicates a missed variant. Use two fixed poses and return screenshots at accept-or-reject points only, not after every edit.

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.