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Particles: spawn particles on mesh surface

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This commit is contained in:
Jacques Lucke
2020-07-23 22:30:05 +02:00
parent c049fe7979
commit f359672c35
8 changed files with 407 additions and 50 deletions
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263
source/blender/simulation/intern/particle_mesh_emitter.cc
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@@ -18,6 +18,9 @@
#include "BLI_float4x4.hh"
#include "BLI_rand.hh"
#include "BLI_vector_adaptor.hh"
#include "BKE_mesh_runtime.h"
#include "DNA_mesh_types.h"
#include "DNA_meshdata_types.h"
@@ -26,14 +29,14 @@
namespace blender::sim {
struct EmitterSettings {
const Object *object;
Object *object;
float rate;
};
static void compute_birth_times(float rate,
TimeInterval emit_interval,
ParticleMeshEmitterSimulationState &state,
Vector<float> &r_birth_times)
static BLI_NOINLINE void compute_birth_times(float rate,
TimeInterval emit_interval,
ParticleMeshEmitterSimulationState &state,
Vector<float> &r_birth_times)
{
const float time_between_particles = 1.0f / rate;
int counter = 0;
@@ -51,51 +54,237 @@ static void compute_birth_times(float rate,
}
}
static void compute_new_particle_attributes(EmitterSettings &settings,
TimeInterval emit_interval,
ParticleMeshEmitterSimulationState &state,
Vector<float3> &r_positions,
Vector<float3> &r_velocities,
Vector<float> &r_birth_times)
static BLI_NOINLINE Span<MLoopTri> get_mesh_triangles(Mesh &mesh)
{
if (settings.object == nullptr) {
const MLoopTri *triangles = BKE_mesh_runtime_looptri_ensure(&mesh);
int amount = BKE_mesh_runtime_looptri_len(&mesh);
return Span(triangles, amount);
}
static BLI_NOINLINE void compute_triangle_areas(Mesh &mesh,
Span<MLoopTri> triangles,
MutableSpan<float> r_areas)
{
assert_same_size(triangles, r_areas);
for (int i : triangles.index_range()) {
const MLoopTri &tri = triangles[i];
const float3 v1 = mesh.mvert[mesh.mloop[tri.tri[0]].v].co;
const float3 v2 = mesh.mvert[mesh.mloop[tri.tri[1]].v].co;
const float3 v3 = mesh.mvert[mesh.mloop[tri.tri[2]].v].co;
const float area = area_tri_v3(v1, v2, v3);
r_areas[i] = area;
}
}
static BLI_NOINLINE void compute_triangle_weights(Mesh &mesh,
Span<MLoopTri> triangles,
MutableSpan<float> r_weights)
{
assert_same_size(triangles, r_weights);
compute_triangle_areas(mesh, triangles, r_weights);
}
static BLI_NOINLINE void compute_cumulative_distribution(Span<float> weights,
MutableSpan<float> r_cumulative_weights)
{
BLI_assert(weights.size() + 1 == r_cumulative_weights.size());
r_cumulative_weights[0] = 0;
for (int i : weights.index_range()) {
r_cumulative_weights[i + 1] = r_cumulative_weights[i] + weights[i];
}
}
static void sample_cumulative_distribution_recursive(RandomNumberGenerator &rng,
int amount,
int start,
int one_after_end,
Span<float> cumulative_weights,
VectorAdaptor<int> &r_sampled_indices)
{
BLI_assert(start <= one_after_end);
const int size = one_after_end - start;
if (size == 0) {
BLI_assert(amount == 0);
}
else if (amount == 0) {
return;
}
if (settings.rate <= 0.000001f) {
return;
else if (size == 1) {
r_sampled_indices.append_n_times(start, amount);
}
if (settings.object->type != OB_MESH) {
return;
else {
const int middle = start + size / 2;
const float left_weight = cumulative_weights[middle] - cumulative_weights[start];
const float right_weight = cumulative_weights[one_after_end] - cumulative_weights[middle];
BLI_assert(left_weight >= 0.0f && right_weight >= 0.0f);
const float weight_sum = left_weight + right_weight;
BLI_assert(weight_sum > 0.0f);
const float left_factor = left_weight / weight_sum;
const float right_factor = right_weight / weight_sum;
int left_amount = amount * left_factor;
int right_amount = amount * right_factor;
if (left_amount + right_amount < amount) {
BLI_assert(left_amount + right_amount + 1 == amount);
const float weight_per_item = weight_sum / amount;
const float total_remaining_weight = weight_sum -
(left_amount + right_amount) * weight_per_item;
const float left_remaining_weight = left_weight - left_amount * weight_per_item;
const float left_remaining_factor = left_remaining_weight / total_remaining_weight;
if (rng.get_float() < left_remaining_factor) {
left_amount++;
}
else {
right_amount++;
}
}
sample_cumulative_distribution_recursive(
rng, left_amount, start, middle, cumulative_weights, r_sampled_indices);
sample_cumulative_distribution_recursive(
rng, right_amount, middle, one_after_end, cumulative_weights, r_sampled_indices);
}
const Mesh &mesh = *(Mesh *)settings.object->data;
if (mesh.totvert == 0) {
return;
}
static BLI_NOINLINE void sample_cumulative_distribution(RandomNumberGenerator &rng,
Span<float> cumulative_weights,
MutableSpan<int> r_samples)
{
VectorAdaptor<int> sampled_indices(r_samples);
sample_cumulative_distribution_recursive(rng,
r_samples.size(),
0,
cumulative_weights.size() - 1,
cumulative_weights,
sampled_indices);
BLI_assert(sampled_indices.is_full());
}
static BLI_NOINLINE bool sample_weighted_buckets(RandomNumberGenerator &rng,
Span<float> weights,
MutableSpan<int> r_samples)
{
Array<float> cumulative_weights(weights.size() + 1);
compute_cumulative_distribution(weights, cumulative_weights);
if (r_samples.size() > 0 && cumulative_weights.as_span().last() == 0.0f) {
/* All weights are zero. */
return false;
}
float4x4 local_to_world = settings.object->obmat;
sample_cumulative_distribution(rng, cumulative_weights, r_samples);
return true;
}
static BLI_NOINLINE void sample_looptris(RandomNumberGenerator &rng,
Mesh &mesh,
Span<MLoopTri> triangles,
Span<int> triangles_to_sample,
MutableSpan<float3> r_sampled_positions,
MutableSpan<float3> r_sampled_normals)
{
assert_same_size(triangles_to_sample, r_sampled_positions, r_sampled_normals);
MLoop *loops = mesh.mloop;
MVert *verts = mesh.mvert;
for (uint i : triangles_to_sample.index_range()) {
const uint triangle_index = triangles_to_sample[i];
const MLoopTri &triangle = triangles[triangle_index];
const float3 v1 = verts[loops[triangle.tri[0]].v].co;
const float3 v2 = verts[loops[triangle.tri[1]].v].co;
const float3 v3 = verts[loops[triangle.tri[2]].v].co;
const float3 bary_coords = rng.get_barycentric_coordinates();
float3 position;
interp_v3_v3v3v3(position, v1, v2, v3, bary_coords);
float3 normal;
normal_tri_v3(normal, v1, v2, v3);
r_sampled_positions[i] = position;
r_sampled_normals[i] = normal;
}
}
static BLI_NOINLINE bool compute_new_particle_attributes(EmitterSettings &settings,
TimeInterval emit_interval,
ParticleMeshEmitterSimulationState &state,
Vector<float3> &r_positions,
Vector<float3> &r_velocities,
Vector<float> &r_birth_times)
{
if (settings.object == nullptr) {
return false;
}
if (settings.rate <= 0.000001f) {
return false;
}
if (settings.object->type != OB_MESH) {
return false;
}
Mesh &mesh = *(Mesh *)settings.object->data;
if (mesh.totvert == 0) {
return false;
}
const float4x4 local_to_world = settings.object->obmat;
float4x4 local_to_world_normal = local_to_world.inverted_affine().transposed();
const float start_time = emit_interval.start();
const uint32_t seed = DefaultHash<StringRef>{}(state.head.name);
RandomNumberGenerator rng{(*(uint32_t *)&start_time) ^ seed};
compute_birth_times(settings.rate, emit_interval, state, r_birth_times);
if (r_birth_times.is_empty()) {
return;
const int particle_amount = r_birth_times.size();
if (particle_amount == 0) {
return false;
}
rng.shuffle(r_birth_times.as_mutable_span());
Span<MLoopTri> triangles = get_mesh_triangles(mesh);
if (triangles.is_empty()) {
return false;
}
Array<float> triangle_weights(triangles.size());
compute_triangle_weights(mesh, triangles, triangle_weights);
Array<int> triangles_to_sample(particle_amount);
if (!sample_weighted_buckets(rng, triangle_weights, triangles_to_sample)) {
return false;
}
Array<float3> local_positions(particle_amount);
Array<float3> local_normals(particle_amount);
sample_looptris(rng, mesh, triangles, triangles_to_sample, local_positions, local_normals);
r_positions.reserve(particle_amount);
r_velocities.reserve(particle_amount);
for (int i : IndexRange(particle_amount)) {
float3 position = local_to_world * local_positions[i];
float3 normal = local_to_world_normal.ref_3x3() * local_normals[i];
normal.normalize();
r_positions.append(position);
r_velocities.append(normal);
}
state.last_birth_time = r_birth_times.last();
for (int i : r_birth_times.index_range()) {
UNUSED_VARS(i);
const int vertex_index = rng.get_int32() % mesh.totvert;
float3 vertex_position = mesh.mvert[vertex_index].co;
r_positions.append(local_to_world * vertex_position);
r_velocities.append(rng.get_unit_float3());
}
return true;
}
static EmitterSettings compute_settings(const fn::MultiFunction &inputs_fn,
ParticleEmitterContext &context)
static BLI_NOINLINE EmitterSettings compute_settings(const fn::MultiFunction &inputs_fn,
ParticleEmitterContext &context)
{
EmitterSettings parameters;
@@ -126,8 +315,14 @@ void ParticleMeshEmitter::emit(ParticleEmitterContext &context) const
Vector<float3> new_velocities;
Vector<float> new_birth_times;
compute_new_particle_attributes(
settings, context.emit_interval(), *state, new_positions, new_velocities, new_birth_times);
if (!compute_new_particle_attributes(settings,
context.emit_interval(),
*state,
new_positions,
new_velocities,
new_birth_times)) {
return;
}
for (StringRef name : particle_names_) {
ParticleAllocator *allocator = context.try_get_particle_allocator(name);