topical media & game development
lib-unity-example-procedural-Assets-Sources-TronTrail.js / js
/*
Generates a trail that is always facing upwards using the scriptable mesh interface.
vertex colors and uv's are generated similar to the builtin Trail Renderer.
To use it
1. create an empty game object
2. attach this script and a MeshRenderer
3. Then assign a particle material to the mesh renderer
*/
var height = 2.0;
var time = 2.0;
var alwaysUp = false;
var minDistance = 0.1;
var startColor = Color.white;
var endColor = Color (1, 1, 1, 0);
class TronTrailSection
{
var point : Vector3;
var upDir : Vector3;
var time : float;
}
private var sections = new Array();
function LateUpdate () {
var position = transform.position;
var now = Time.time;
// Remove old sections
while (sections.length > 0 && now > sections[sections.length - 1].time + time) {
sections.Pop();
}
// Add a new trail section
if (sections.length == 0 || (sections[0].point - position).sqrMagnitude > minDistance * minDistance)
{
var section = TronTrailSection ();
section.point = position;
if (alwaysUp)
section.upDir = Vector3.up;
else
section.upDir = transform.TransformDirection(Vector3.up);
section.time = now;
sections.Unshift(section);
}
// Rebuild the mesh
var mesh : Mesh = GetComponent(MeshFilter).mesh;
mesh.Clear();
// We need at least 2 sections to create the line
if (sections.length < 2)
return;
var vertices = new Vector3[sections.length * 2];
var colors = new Color[sections.length * 2];
var uv = new Vector2[sections.length * 2];
var previousSection : TronTrailSection = sections[0];
var currentSection : TronTrailSection = sections[0];
// Use matrix instead of transform.TransformPoint for performance reasons
var localSpaceTransform = transform.worldToLocalMatrix;
// Generate vertex, uv and colors
for (var i=0;i<sections.length;i++)
{
previousSection = currentSection;
currentSection = sections[i];
// Calculate u for texture uv and color interpolation
var u = 0.0;
if (i != 0)
u = Mathf.Clamp01 ((Time.time - currentSection.time) / time);
// Calculate upwards direction
var upDir = currentSection.upDir;
// Generate vertices
vertices[i * 2 + 0] = localSpaceTransform.MultiplyPoint(currentSection.point);
vertices[i * 2 + 1] = localSpaceTransform.MultiplyPoint(currentSection.point + upDir * height);
uv[i * 2 + 0] = Vector2(u, 0);
uv[i * 2 + 1] = Vector2(u, 1);
// fade colors out over time
var interpolatedColor = Color.Lerp(startColor, endColor, u);
colors[i * 2 + 0] = interpolatedColor;
colors[i * 2 + 1] = interpolatedColor;
}
// Generate triangles indices
var triangles = new int[(sections.length - 1) * 2 * 3];
for (i=0;i<triangles.length / 6;i++)
{
triangles[i * 6 + 0] = i * 2;
triangles[i * 6 + 1] = i * 2 + 1;
triangles[i * 6 + 2] = i * 2 + 2;
triangles[i * 6 + 3] = i * 2 + 2;
triangles[i * 6 + 4] = i * 2 + 1;
triangles[i * 6 + 5] = i * 2 + 3;
}
// Assign to mesh
mesh.vertices = vertices;
mesh.colors = colors;
mesh.uv = uv;
mesh.triangles = triangles;
}
@script RequireComponent (MeshFilter)
(C) Æliens
04/09/2009
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