get the id offset

@brief != operator @param other Comparing with the other StringID.

operator to get a point from the ray para 't' : the distance from the retrieve point if the direction of the ray is normalized. reslut : A point

transform a ray para 'r' : the ray to transform result : transformed ray

matrix mutiplication

Comparator for the struct. @param split The split plane to compare with. @return A comparing result based on position and type of the spli

@brief Helper function to check whether sid_t equals to StringID

@brief == operator @param other Comparing with the other StringID.

@brief Return value in specific channel. It is the upper level code's repsonsibility to make sure that i is within valid range. Otherwise, it is ver

@brief Get the data of specific channel. @param id Index of channel of interest. @return Value of channel of interest.

Appending '_sid' converts a string to StringID, which is essentially an unsigned integer.

transform a ray

operator for transform

@brief Access value in a specific channel. It is up to the higher level code to make sure id is with the valid range. @param id Index of channel

@brief Access value in a specific channel. It is up to the higher level code to make sure id is with the valid range. @param id Index of channel

the pdf for the sampled direction