frustum.py

from settings import *


"""
	Allows only chunks in player's
	frustum (FOV) to be rendered
"""
class Frustum:
	def __init__(self, camera):
		self.cam: Camera = camera

		self.factor_y = 1.0 / math.cos(half_y := V_FOV * 0.5)
		self.tan_y = math.tan(half_y)

		self.factor_x = 1.0 / math.cos(half_x := H_FOV * 0.5)
		self.tan_x = math.tan(half_x)


	def is_on_frustum(self, chunk):
		# vector to center of sphere
		sphere_vec = chunk.center - self.cam.position

		# check if outside the NEAR and FAR planes
		sz = glm.dot(sphere_vec, self.cam.forward)
		if not (NEAR - CHUNK_SPHERE_RADIUS <= sz <= FAR + CHUNK_SPHERE_RADIUS):
			return False

		# check if outside TOP and BOTTOM planes
		sy = glm.dot(sphere_vec, self.cam.up)
		dist = self.factor_y * CHUNK_SPHERE_RADIUS + sz * self.tan_y
		if not (-dist <= sy <= dist):
			return False

		# check if outside LEFT and RIGHT planes
		sx = glm.dot(sphere_vec, self.cam.right)
		dist = self.factor_x * CHUNK_SPHERE_RADIUS + sz * self.tan_x
		if not (-dist <= sx <= dist):
			return False

		return True