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CPUParticles2D - Add ability to follow physics interpolated target

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Allows a non-interpolated particle system to closely follow an interpolated target without tracking ahead of the target, by performing fixed timestep interpolation on the particle system global transform, and using this for emission.

Co-authored-by: lawnjelly <lawnjelly@gmail.com>
This commit is contained in:
Ricardo Buring 2025-01-22 13:24:55 +01:00
parent a7146ef807
commit 56fc0fd175
12 changed files with 157 additions and 34 deletions
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102
scene/2d/cpu_particles_2d.cpp
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@ -32,6 +32,7 @@
#include "cpu_particles_2d.compat.inc"
#include "core/math/random_number_generator.h"
#include "core/math/transform_interpolator.h"
#include "scene/2d/gpu_particles_2d.h"
#include "scene/resources/atlas_texture.h"
#include "scene/resources/canvas_item_material.h"
@ -96,7 +97,14 @@ void CPUParticles2D::set_lifetime_randomness(double p_random) {
void CPUParticles2D::set_use_local_coordinates(bool p_enable) {
local_coords = p_enable;
set_notify_transform(!p_enable);
// Prevent sending item transforms when using global coords,
// and inform the RenderingServer to use identity mode.
set_canvas_item_use_identity_transform(!local_coords);
// We only need NOTIFICATION_TRANSFORM_CHANGED
// when following an interpolated target.
set_notify_transform(_interpolation_data.interpolated_follow);
}
void CPUParticles2D::set_speed_scale(double p_scale) {
@ -228,6 +236,27 @@ void CPUParticles2D::_texture_changed() {
}
}
void CPUParticles2D::_refresh_interpolation_state() {
if (!is_inside_tree()) {
return;
}
// The logic for whether to do an interpolated follow.
// This is rather complex, but basically:
// If project setting interpolation is ON and this particle system is in global mode,
// we will follow the INTERPOLATED position rather than the actual position.
// This is so that particles aren't generated AHEAD of the interpolated parent.
bool follow = !local_coords && get_tree()->is_physics_interpolation_enabled();
if (follow == _interpolation_data.interpolated_follow) {
return;
}
_interpolation_data.interpolated_follow = follow;
set_physics_process_internal(_interpolation_data.interpolated_follow);
}
Ref<Texture2D> CPUParticles2D::get_texture() const {
return texture;
}
@ -600,6 +629,9 @@ void CPUParticles2D::_update_internal() {
return;
}
// Change update mode?
_refresh_interpolation_state();
double delta = get_process_delta_time();
if (!active && !emitting) {
set_process_internal(false);
@ -679,7 +711,11 @@ void CPUParticles2D::_particles_process(double p_delta) {
Transform2D emission_xform;
Transform2D velocity_xform;
if (!local_coords) {
emission_xform = get_global_transform();
if (!_interpolation_data.interpolated_follow) {
emission_xform = get_global_transform();
} else {
TransformInterpolator::interpolate_transform_2d(_interpolation_data.global_xform_prev, _interpolation_data.global_xform_curr, emission_xform, Engine::get_singleton()->get_physics_interpolation_fraction());
}
velocity_xform = emission_xform;
velocity_xform[2] = Vector2();
}
@ -1142,6 +1178,17 @@ void CPUParticles2D::_notification(int p_what) {
switch (p_what) {
case NOTIFICATION_ENTER_TREE: {
set_process_internal(emitting);
_refresh_interpolation_state();
set_physics_process_internal(emitting && _interpolation_data.interpolated_follow);
// If we are interpolated following, then reset physics interpolation
// when first appearing. This won't be called by canvas item, as in the
// following mode, is_physics_interpolated() is actually FALSE.
if (_interpolation_data.interpolated_follow) {
notification(NOTIFICATION_RESET_PHYSICS_INTERPOLATION);
}
} break;
case NOTIFICATION_EXIT_TREE: {
@ -1170,37 +1217,28 @@ void CPUParticles2D::_notification(int p_what) {
_update_internal();
} break;
case NOTIFICATION_INTERNAL_PHYSICS_PROCESS: {
if (_interpolation_data.interpolated_follow) {
// Keep the interpolated follow target updated.
_interpolation_data.global_xform_prev = _interpolation_data.global_xform_curr;
_interpolation_data.global_xform_curr = get_global_transform();
}
} break;
case NOTIFICATION_TRANSFORM_CHANGED: {
inv_emission_transform = get_global_transform().affine_inverse();
if (!local_coords) {
int pc = particles.size();
float *w = particle_data.ptrw();
const Particle *r = particles.ptr();
float *ptr = w;
for (int i = 0; i < pc; i++) {
Transform2D t = inv_emission_transform * r[i].transform;
if (r[i].active) {
ptr[0] = t.columns[0][0];
ptr[1] = t.columns[1][0];
ptr[2] = 0;
ptr[3] = t.columns[2][0];
ptr[4] = t.columns[0][1];
ptr[5] = t.columns[1][1];
ptr[6] = 0;
ptr[7] = t.columns[2][1];
} else {
memset(ptr, 0, sizeof(float) * 8);
}
ptr += 16;
if (_interpolation_data.interpolated_follow) {
// If the transform has been updated AFTER the physics tick, keep data flowing.
if (Engine::get_singleton()->is_in_physics_frame()) {
_interpolation_data.global_xform_curr = get_global_transform();
}
}
} break;
case NOTIFICATION_RESET_PHYSICS_INTERPOLATION: {
// Make sure current is up to date with any pending global transform changes.
_interpolation_data.global_xform_curr = get_global_transform_const();
_interpolation_data.global_xform_prev = _interpolation_data.global_xform_curr;
} break;
}
}
@ -1559,6 +1597,12 @@ CPUParticles2D::CPUParticles2D() {
set_color(Color(1, 1, 1, 1));
_update_mesh_texture();
// CPUParticles2D defaults to interpolation off.
// This is because the result often looks better when the particles are updated every frame.
// Note that children will need to explicitly turn back on interpolation if they want to use it,
// rather than relying on inherit mode.
set_physics_interpolation_mode(Node::PHYSICS_INTERPOLATION_MODE_OFF);
}
CPUParticles2D::~CPUParticles2D() {