private void GenerateMesh(out Mesh mesh, out Mesh meshDebug)
{
mesh = new Mesh();
meshDebug = new Mesh {
vertices = carrierMesh.vertices, triangles = carrierMesh.triangles, uv = carrierMesh.uv
};
Vector3 particleAverageNormal = Vector3.zero;
for (int i = 0; i < particleMesh.vertexCount; i++)
{
particleAverageNormal += particleMesh.normals[i];
}
particleAverageNormal.Normalize();
var numTriangles = carrierMesh.triangles.Length / 3;
CombineInstance[] combine = new CombineInstance[numParticles];
for (int i = 0; i < numParticles; i++)
{
var particle = new Mesh {
vertices = particleMesh.vertices,
triangles = particleMesh.triangles,
colors = particleMesh.colors,
normals = particleMesh.normals,
tangents = particleMesh.tangents,
uv = particleMesh.uv,
};
int triangleIndex = carrierSampling == CarrierSampling.Random
? Random.Range(0, numTriangles)
: (int)Mathf.Lerp(0, numTriangles, i / (float)numParticles);
var vertexIndex0 = carrierMesh.triangles[triangleIndex * 3 + 0];
var vertexIndex1 = carrierMesh.triangles[triangleIndex * 3 + 1];
var vertexIndex2 = carrierMesh.triangles[triangleIndex * 3 + 2];
var a = carrierMesh.vertices[vertexIndex0];
var b = carrierMesh.vertices[vertexIndex1];
var c = carrierMesh.vertices[vertexIndex2];
var p = GetRandomPositionWithinTriangle(a, b, c);
p = Vector3.Scale(p, carrierScale);
var triangleNormal = (carrierMesh.normals[vertexIndex0] + carrierMesh.normals[vertexIndex1] +
carrierMesh.normals[vertexIndex2]).normalized;
var triangleTangent = (carrierMesh.tangents[vertexIndex0] + carrierMesh.tangents[vertexIndex1] +
carrierMesh.tangents[vertexIndex2]).normalized;
if (Random.value <= offsetAlongNormalFraction)
{
p += triangleNormal * offsetAlongNormal;
}
var up = Vector3.Cross(triangleNormal, triangleTangent);
var rotation = Quaternion.LookRotation(-triangleNormal, up);
// Random rotation for particle clouds.
rotation = Quaternion.RotateTowards(rotation, Random.rotationUniform, particleRotationRange);
// Rotation bias for billboard meshes.
var biasTowards = Quaternion.Euler(biasTowardRotation);
rotation = Quaternion.RotateTowards(rotation, biasTowards, 180f * particleRotationBias);
// Give the particle a random forward rotation.
rotation *= Quaternion.AngleAxis(360f * Random.value, particleAverageNormal);
var scaleVariance = Random.Range(1f - particleScaleVariance, 1f);
var particleTransform = Matrix4x4.Translate(p) * Matrix4x4.Rotate(rotation) *
Matrix4x4.Scale(particleScale * scaleVariance) * Matrix4x4.identity;
var combineInstance = new CombineInstance {
mesh = particle, transform = particleTransform
};
combine[i] = combineInstance;
}
mesh.CombineMeshes(combine, true, true);
// Calculate normals.
{
var normals = new Vector3[mesh.vertexCount];
for (int i = 0; i < normals.Length; i++)
{
int vertexIndex = oneNormalPerParticle ? i - i % particleMesh.vertexCount : i;
var v = mesh.vertices[vertexIndex].normalized;
Vector3 noise = Vector3.zero;
if (noiseEnabled)
{
var nv = v * noiseFrequency;
var nx = NoiseUtil.Fbm(Hash.Float(noiseSeed, 0u, -1000, 1000), nv.x, noiseOctaves);
var ny = NoiseUtil.Fbm(Hash.Float(noiseSeed, 1u, -1000, 1000), nv.y, noiseOctaves);
var nz = NoiseUtil.Fbm(Hash.Float(noiseSeed, 2u, -1000, 1000), nv.z, noiseOctaves);
noise = Vector3.Scale(new Vector3(nx, ny, nz), noiseScale) / 0.75f * noiseAmplitude;
}
normals[i] = (v + noise).normalized;
}
mesh.normals = normals;
}
}