Add "Hide on Contact" collision mode to ParticlesMaterial

This can be used to make particles disappear when colliding, rather
than bouncing around or sticking to surfaces.

This is useful for rain particles which should not be able to go
through floors/ceilings, but shouldn't stick to surfaces either.

1 files changed, 40 insertions, 12 deletions

diff --git a/scene/resources/particles_material.cpp b/scene/resources/particles_material.cpp
index 4b2e029f47..7c27766d7c 100644
--- a/scene/resources/particles_material.cpp
+++ b/scene/resources/particles_material.cpp
@@ -287,7 +287,7 @@ void ParticlesMaterial::_update_shader() {
 		code += "uniform sampler2D anim_offset_texture : repeat_disable;\n";
 	}
 
-	if (collision_enabled) {
+	if (collision_mode == COLLISION_RIGID) {
 		code += "uniform float collision_friction;\n";
 		code += "uniform float collision_bounce;\n";
 	}
@@ -695,8 +695,10 @@ void ParticlesMaterial::_update_shader() {
 		}
 		code += "	vec3 noise_direction = get_noise_direction(TRANSFORM[3].xyz, EMISSION_TRANSFORM[3].xyz, time_noise);\n";
 		// If collision happened, turbulence is no longer applied.
+		// We don't need this check when the collision mode is "hide on contact",
+		// as the particle will be hidden anyway.
 		String extra_tab = "";
-		if (collision_enabled) {
+		if (collision_mode != COLLISION_RIGID) {
 			code += "	if (!COLLIDED) {\n";
 			extra_tab = "	";
 		}
@@ -704,7 +706,7 @@ void ParticlesMaterial::_update_shader() {
 		code += extra_tab + "	float vel_mag = length(VELOCITY);\n";
 		code += extra_tab + "	float vel_infl = clamp(mix(turbulence_influence_min, turbulence_influence_max, rand_from_seed(alt_seed)) * turbulence_influence, 0.0, 1.0);\n";
 		code += extra_tab + "	VELOCITY = mix(VELOCITY, normalize(noise_direction) * vel_mag * (1.0 + (1.0 - vel_infl) * 0.2), vel_infl);\n";
-		if (collision_enabled) {
+		if (collision_mode != COLLISION_RIGID) {
 			code += "	}";
 		}
 	}
@@ -828,7 +830,7 @@ void ParticlesMaterial::_update_shader() {
 		code += "	TRANSFORM[3].z = 0.0;\n";
 	}
 
-	if (collision_enabled) {
+	if (collision_mode == COLLISION_RIGID) {
 		code += "	if (COLLIDED) {\n";
 		code += "		if (length(VELOCITY) > 3.0) {\n";
 		code += "			TRANSFORM[3].xyz += COLLISION_NORMAL * COLLISION_DEPTH;\n";
@@ -851,6 +853,18 @@ void ParticlesMaterial::_update_shader() {
 	code += "	TRANSFORM[1].xyz *= base_scale * sign(tex_scale.g) * max(abs(tex_scale.g), 0.001);\n";
 	code += "	TRANSFORM[2].xyz *= base_scale * sign(tex_scale.b) * max(abs(tex_scale.b), 0.001);\n";
 
+	if (collision_mode == COLLISION_RIGID) {
+		code += "	if (COLLIDED) {\n";
+		code += "		TRANSFORM[3].xyz+=COLLISION_NORMAL * COLLISION_DEPTH;\n";
+		code += "		VELOCITY -= COLLISION_NORMAL * dot(COLLISION_NORMAL, VELOCITY) * (1.0 + collision_bounce);\n";
+		code += "		VELOCITY = mix(VELOCITY,vec3(0.0),collision_friction * DELTA * 100.0);\n";
+		code += "	}\n";
+	} else if (collision_mode == COLLISION_HIDE_ON_CONTACT) {
+		code += "	if (COLLIDED) {\n";
+		code += "		ACTIVE = false;\n";
+		code += "	}\n";
+	}
+
 	if (sub_emitter_mode != SUB_EMITTER_DISABLED) {
 		code += "	int emit_count = 0;\n";
 		switch (sub_emitter_mode) {
@@ -1436,6 +1450,14 @@ void ParticlesMaterial::_validate_property(PropertyInfo &property) const {
 			property.usage = PROPERTY_USAGE_NO_EDITOR;
 		}
 	}
+
+	if (property.name == "collision_friction" && collision_mode != COLLISION_RIGID) {
+		property.usage = PROPERTY_USAGE_NONE;
+	}
+
+	if (property.name == "collision_bounce" && collision_mode != COLLISION_RIGID) {
+		property.usage = PROPERTY_USAGE_NONE;
+	}
 }
 
 void ParticlesMaterial::set_sub_emitter_mode(SubEmitterMode p_sub_emitter_mode) {
@@ -1483,13 +1505,14 @@ bool ParticlesMaterial::is_attractor_interaction_enabled() const {
 	return attractor_interaction_enabled;
 }
 
-void ParticlesMaterial::set_collision_enabled(bool p_enabled) {
-	collision_enabled = p_enabled;
+void ParticlesMaterial::set_collision_mode(CollisionMode p_collision_mode) {
+	collision_mode = p_collision_mode;
 	_queue_shader_change();
+	notify_property_list_changed();
 }
 
-bool ParticlesMaterial::is_collision_enabled() const {
-	return collision_enabled;
+ParticlesMaterial::CollisionMode ParticlesMaterial::get_collision_mode() const {
+	return collision_mode;
 }
 
 void ParticlesMaterial::set_collision_use_scale(bool p_scale) {
@@ -1623,8 +1646,8 @@ void ParticlesMaterial::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_attractor_interaction_enabled", "enabled"), &ParticlesMaterial::set_attractor_interaction_enabled);
 	ClassDB::bind_method(D_METHOD("is_attractor_interaction_enabled"), &ParticlesMaterial::is_attractor_interaction_enabled);
 
-	ClassDB::bind_method(D_METHOD("set_collision_enabled", "enabled"), &ParticlesMaterial::set_collision_enabled);
-	ClassDB::bind_method(D_METHOD("is_collision_enabled"), &ParticlesMaterial::is_collision_enabled);
+	ClassDB::bind_method(D_METHOD("set_collision_mode", "mode"), &ParticlesMaterial::set_collision_mode);
+	ClassDB::bind_method(D_METHOD("get_collision_mode"), &ParticlesMaterial::get_collision_mode);
 
 	ClassDB::bind_method(D_METHOD("set_collision_use_scale", "radius"), &ParticlesMaterial::set_collision_use_scale);
 	ClassDB::bind_method(D_METHOD("is_collision_using_scale"), &ParticlesMaterial::is_collision_using_scale);
@@ -1734,7 +1757,7 @@ void ParticlesMaterial::_bind_methods() {
 	ADD_GROUP("Attractor Interaction", "attractor_interaction_");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "attractor_interaction_enabled"), "set_attractor_interaction_enabled", "is_attractor_interaction_enabled");
 	ADD_GROUP("Collision", "collision_");
-	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "collision_enabled"), "set_collision_enabled", "is_collision_enabled");
+	ADD_PROPERTY(PropertyInfo(Variant::INT, "collision_mode", PROPERTY_HINT_ENUM, "Disabled,Rigid,Hide On Contact"), "set_collision_mode", "get_collision_mode");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "collision_friction", PROPERTY_HINT_RANGE, "0,1,0.01"), "set_collision_friction", "get_collision_friction");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "collision_bounce", PROPERTY_HINT_RANGE, "0,1,0.01"), "set_collision_bounce", "get_collision_bounce");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "collision_use_scale"), "set_collision_use_scale", "is_collision_using_scale");
@@ -1776,6 +1799,11 @@ void ParticlesMaterial::_bind_methods() {
 	BIND_ENUM_CONSTANT(SUB_EMITTER_AT_END);
 	BIND_ENUM_CONSTANT(SUB_EMITTER_AT_COLLISION);
 	BIND_ENUM_CONSTANT(SUB_EMITTER_MAX);
+
+	BIND_ENUM_CONSTANT(COLLISION_DISABLED);
+	BIND_ENUM_CONSTANT(COLLISION_RIGID);
+	BIND_ENUM_CONSTANT(COLLISION_HIDE_ON_CONTACT);
+	BIND_ENUM_CONSTANT(COLLISION_MAX);
 }
 
 ParticlesMaterial::ParticlesMaterial() :
@@ -1834,7 +1862,7 @@ ParticlesMaterial::ParticlesMaterial() :
 	set_sub_emitter_keep_velocity(false);
 
 	set_attractor_interaction_enabled(true);
-	set_collision_enabled(false);
+	set_collision_mode(COLLISION_DISABLED);
 	set_collision_bounce(0.0);
 	set_collision_friction(0.0);
 	set_collision_use_scale(false);