// Function Add is called by the wheels that is skidding.
// Gathers all the information needed to create the mesh later in LateUpdate.
// It sets the intensity of the skidmark segment by setting the alpha
// of the vertex color.
public int Add(Vector3 pos, Vector3 normal, float intensity, int lastIndex)
{
// reduce intensity for min. alpha blending (= opaque)
if (intensity > 1)
{
intensity = 1.0f;
}
// finsih skidmark with an intensity lower than zero
if (intensity < 0)
{
return(-1);
}
// init new skidmark at index numMarks%maxMark (overwritting old ones)
markSegment curr = skidmarks[numMarks % maxMarks];
curr.pos = pos + normal * groundOffset;
curr.normal = normal;
curr.intensity = intensity;
curr.lastIndex = lastIndex;
// if it is not the first skidmark position
if (lastIndex != -1)
{
// get the last mark to attach the new mark
markSegment last = skidmarks[lastIndex % maxMarks];
// compute the direction & perpendicular vector of the new mark
Vector3 dir = curr.pos - last.pos;
Vector3 perpDir = Vector3.Cross(dir, normal).normalized;
Vector3 perpHalfWidth = perpDir * markWidth * 0.5f;
curr.posl = curr.pos + perpHalfWidth;
curr.posr = curr.pos - perpHalfWidth;
curr.tangent = new Vector4(perpDir.x, perpDir.y, perpDir.z, 1);
// if it is the second skidmark position finish the data of the 1st pos.
if (last.lastIndex == -1)
{
last.tangent = curr.tangent;
last.posl = curr.pos + perpHalfWidth;
last.posr = curr.pos - perpHalfWidth;
}
}
numMarks++;
updateMesh = true;
// return index of the new mark
return(numMarks - 1);
}
private bool updateMesh = false; // flag if mesh mus
// Initiallization and creation of objects
void Awake()
{
// Init the array that holds the skidmarks
skidmarks = new markSegment[maxMarks];
for (var i = 0; i < maxMarks; i++)
{
skidmarks[i] = new markSegment();
}
// Create the game object that shows the skidmarks at runtime
_skidmarkMesh = new GameObject("Skidmarks");
MeshRenderer mr = _skidmarkMesh.AddComponent <MeshRenderer>();
MeshFilter mf = _skidmarkMesh.AddComponent <MeshFilter>();
mr.material = material;
if (mf.mesh == null)
{
mf.mesh = new Mesh();
}
}
void LateUpdate()
{
if (!updateMesh)
{
return;
}
// get the mesh & clear all data
Mesh mesh = _skidmarkMesh.GetComponent <MeshFilter>().mesh;
mesh.Clear();
// count all segments in the array skidmark that are used
int segmentCount = 0;
for (int j = 0; j < numMarks && j < maxMarks; j++)
{
if (skidmarks[j].lastIndex != -1 &&
skidmarks[j].lastIndex > numMarks - maxMarks)
{
segmentCount++;
}
}
// create temp. arrays for mesh attributes
int numV = segmentCount * 4; // No. of vertices
int numT = segmentCount * 6; // No. of triangle vertex indexes
Vector3[] vertices = new Vector3[numV]; // vertex positions
Vector3[] normals = new Vector3[numV]; // normal vectors
Vector4[] tangents = new Vector4[numV]; // tangent vectors
Color[] colors = new Color[numV]; // RGBA colors
Vector2[] uvs = new Vector2[numV]; // texture coordinates
int[] triangles = new int[numT]; // triangle vertex indexes
// set mesh data for all segments by looping over the skidmark array
segmentCount = 0;
for (int i = 0; i < numMarks && i < maxMarks; i++)
{
if (skidmarks[i].lastIndex != -1 &&
skidmarks[i].lastIndex > numMarks - maxMarks)
{
markSegment curr = skidmarks[i];
markSegment last = skidmarks[curr.lastIndex % maxMarks];
// Set vertices, normals, tangents & uv-coordinates
numV = segmentCount * 4;
vertices[numV] = last.posl;
vertices[numV + 1] = last.posr;
vertices[numV + 2] = curr.posl;
vertices[numV + 3] = curr.posr;
normals[numV] = last.normal;
normals[numV + 1] = last.normal;
normals[numV + 2] = curr.normal;
normals[numV + 3] = curr.normal;
tangents[numV] = last.tangent;
tangents[numV + 1] = last.tangent;
tangents[numV + 2] = curr.tangent;
tangents[numV + 3] = curr.tangent;
colors[numV] = new Color(0, 0, 0, last.intensity);
colors[numV + 1] = new Color(0, 0, 0, last.intensity);
colors[numV + 2] = new Color(0, 0, 0, curr.intensity);
colors[numV + 3] = new Color(0, 0, 0, curr.intensity);
uvs[numV] = new Vector2(0, 0);
uvs[numV + 1] = new Vector2(1, 0);
uvs[numV + 2] = new Vector2(0, 1);
uvs[numV + 3] = new Vector2(1, 1);
// Set 6 triangle indexes of 2 triangles
numT = segmentCount * 6;
triangles[numT] = numV;
triangles[numT + 2] = numV + 1;
triangles[numT + 1] = numV + 2;
triangles[numT + 3] = numV + 2;
triangles[numT + 5] = numV + 1;
triangles[numT + 4] = numV + 3;
segmentCount++;
}
}
// finally set new attributs to
mesh.vertices = vertices;
mesh.normals = normals;
mesh.tangents = tangents;
mesh.triangles = triangles;
mesh.colors = colors;
mesh.uv = uvs;
updateMesh = false;
}
