glsl - what is the difference between querying time elapsed in OpenGL with GL_TIME_ELAPSED and GL_TIMESTAMP -


both of them can used time elapsed in nanoseconds. former uses scoped glbeginquery/glendquery. difference?

is difference?

you though minor difference.

gl_time_elapsed delivers gpu time took process commands in query's scope (ie: glbegin/end). gl_timestamp not count of anything. merely gets time, in nanoseconds, since... well, something. start time implementation defined, increasing (unless overflows).

to put way, gl_time_elapsed stopwatch: time between when start , stop. it's delta. gl_timestamp looking @ clock: it's increasing. it's absolute time, it's relative implementation dependent.


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