Created
June 6, 2013 00:30
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/* | |
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) |
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