Implementing Web Animation Without an API: Interactive Web Development Part 2

To implement the effect of snow piling up on specific objects, ray casting and orthographic projection techniques are utilized.

The animation of snow accumulating on a star applies the principle of 'ball bouncing.' Ray casting is used to detect the moment snow collides with the star's surface, finding the intersection point between the snow and the star's line segments.

For the intersection point calculation, the slope of the line segment and the rate of change of the y value are used in a 2D coordinate space. It checks whether the snow's y-coordinate is within the line segment's y-range, and derives the exact x-coordinate through the rate of change, setting the snow's velocity to 0 to stop the snow.

For the tree, orthographic projection is applied so that snow piles up precisely on the curve, implementing the snow's placement to follow the shape of the curve.