spikes.qgis

Use symbology > centroid > geometry generator

# Main spikes :

with_variable(
	'coords', 
	array(x(centroid($geometry)),y(centroid($geometry))), 
	make_triangle(
		make_point(@coords[0] - 8000,
		           @coords[1]),
			   
		make_point(@coords[0], 
			   @coords[1] + nb_cas*30),
			   
		make_point(@coords[0] + 8000, 
		           @coords[1])
	)
)

# Spike shadows :

with_variable(
	'coords', 
	array(x(centroid($geometry)),y(centroid($geometry))), 
	make_triangle(
		make_point(@coords[0] - 8000, 
		           @coords[1]),
		
		make_point(@coords[0] + (cos(pi()/4)*nb_cas*20),
		           @coords[1] - (sin(pi()/4)*nb_cas*20)),
		
		make_point(@coords[0] + 8000, 
		           @coords[1])
	)
)