def _get_noise_at(self, x, y):
"""Get perlin noise at a point in terrain.
Does this by choosing a random gradient vector for each grid corner (done at initialization)
and taking their dot products with the displacement vectors to each point in the grid.
The generated values are then interpolated between based on distance to each corner from the desired point.
Args:
x (int): X coordinate of requested point.
y (int): Y coordinate of requested point.
Returns:
float: Height of point on terrain, between 0 and 1 inclusive.
"""
grid_x = x / float(self._square_len) # X value within grid of gradient vectors
grid_y = y / float(self._square_len) # Y value within grid of gradient vectors
left_x, right_x, upper_y, lower_y = self._get_corners(grid_x, grid_y)
x_weight = grid_x - left_x
y_weight = grid_y - upper_y
# ul = upper left, lr = lower right, etc.
ul_influence_val = self._get_influence_val(left_x, upper_y, grid_x, grid_y)
ur_influence_val = self._get_influence_val(right_x, upper_y, grid_x, grid_y)
ll_influence_val = self._get_influence_val(left_x, lower_y, grid_x, grid_y)
lr_influence_val = self._get_influence_val(right_x, lower_y, grid_x, grid_y)
# Interpolate between top two and bottom two influence vals, then interpolate between them using y_weight
upper_influence_val = self._interpolate_between(ul_influence_val, ur_influence_val, x_weight)
lower_influence_val = self._interpolate_between(ll_influence_val, lr_influence_val, x_weight)
interpolated_val = self._interpolate_between(upper_influence_val, lower_influence_val, y_weight)
# Normalize interpolated_val to be between 0 and 1, return as height
# Can range from 0.5 to -0.5, add 0.5 to achieve proper result
height = interpolated_val + 0.5
# Some margin of error, ensure is still between 0 and 1
return round(height) if not 0 <= height <= 1 else height
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