export default /* glsl */ `
#include <common>
#include <color_pars_vertex>
#include <logdepthbuf_pars_vertex>
#include <clipping_planes_pars_vertex>

#include <tile_pars_vertex>
#include <soft_pars_vertex>

attribute vec3 offset;
attribute float rotation;
attribute vec3 size;
attribute vec4 velocity;

uniform float speedFactor;

void main() {
    float lengthFactor = velocity.w;
    float avgSize = (size.x + size.y) * 0.5;
#ifdef USE_SKEW
    vec4 mvPosition = modelViewMatrix * vec4( offset, 1.0 );
    vec3 viewVelocity = normalMatrix * velocity.xyz;

    vec3 scaledPos = vec3(position.xy * size.xy, position.z);
    float vlength = length(viewVelocity);
    vec3 projVelocity =  dot(scaledPos, viewVelocity) * viewVelocity / vlength;
    mvPosition.xyz += scaledPos + projVelocity * (speedFactor / avgSize + lengthFactor / vlength);
#else
    vec4 mvPosition = modelViewMatrix * vec4( offset, 1.0 );
    vec3 viewVelocity = normalMatrix * velocity.xyz;
    float vlength = length(viewVelocity); 
    mvPosition.xyz += position.y * normalize(cross(mvPosition.xyz, viewVelocity)) * avgSize; // switch the cross to  match unity implementation
    mvPosition.xyz -= (position.x + 0.5) * viewVelocity * (1.0 + lengthFactor / vlength) * avgSize; // minus position.x to match unity implementation
#endif
	vColor = color;
	gl_Position = projectionMatrix * mvPosition;
	#include <logdepthbuf_vertex>
	#include <clipping_planes_vertex>
	#include <tile_vertex>
	#include <soft_vertex>
}
`;
/*

    vec3 instancePos = vec3(position.xy * size, position.z);
    instancePos += dot(instancePos, viewVelocity) * viewVelocity * speedFactor;
    mvPosition.xyz += instancePos;

	vColor = color; //vec4(1, 1, 1, 1); //color; //length(viewVelocity) * 0.1

	#ifndef USE_SIZEATTENUATION
		bool isPerspective = ( projectionMatrix[ 2 ][ 3 ] == - 1.0 );
		if ( isPerspective ) computedSize *= - mvPosition.z;
	#endif
 */