Tunnel Speed Lines

This is a 3D Particles Shader updated for Godot 4, to draw Tunnel Speed Lines.

Tunnel dimensions are set by Tunnel Radius and Tunnel Length.

Velocity is set by Lifetime ( = Preprocess ).

Draw Pass 1 draws Quad-stripes with editable size x=3.0, y=0.4.

Draw Pass 1 Material has a Shader Param Texture Albedo, to use your own texture with alpha channel.

Shader code

// particles shader for Godot 4
shader_type particles;

uniform float tube_radius : hint_range( 0.0, 10.0 ) = 3.0;
uniform float tube_length : hint_range( 0.0, 100.0 ) = 50.0;

float rand_from_seed(inout uint seed) {
	int k;
	int s = int(seed);
	if (s == 0)
	s = 305420679;
	k = s / 127773;
	s = 16807 * (s - k * 127773) - 2836 * k;
	if (s < 0)
		s += 2147483647;
	seed = uint(s);
	return float(seed % uint(65536)) / 65535.0;
}

uint hash(uint x) {
	x = ((x >> uint(16)) ^ x) * uint(73244475);
	x = ((x >> uint(16)) ^ x) * uint(73244475);
	x = (x >> uint(16)) ^ x;
	return x;
}

void start() {
	if (RESTART_VELOCITY) {
		VELOCITY = (EMISSION_TRANSFORM * vec4( -tube_length / LIFETIME * 1.0, 0.0, 0.0, 0.0)).xyz;
	}
	if (RESTART_POSITION) {
		uint alt_seed1 = hash(NUMBER + uint(1) + RANDOM_SEED);
		// set particle position by tube_radius and tube_length
		float a = rand_from_seed( alt_seed1 ) * TAU;
		TRANSFORM = mat4(
			vec4( 1.0,0.0,0.0,0.0 ),
			vec4( 0.0,sin(a),-cos(a),0.0 ),
			vec4( 0.0,-cos(a),sin(a),0.0 ),
			vec4( tube_length, sin( a + PI ) * tube_radius, cos( a + PI ) * tube_radius, 1.0 )
		);
		TRANSFORM = EMISSION_TRANSFORM * TRANSFORM;
	}
}

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