Why isn't the 3rd parameter of gvdbBrickFunc2_t passed by reference?

[nvidia]

Why isn't the 3rd parameter of gvdbBrickFunc2_t passed by reference?

[ramakarl]

Take a look at STEP_DDA which immediately follows the brickFunc call.
The next instruction there is t.x=t.y, which sets the t value to the exit point residing on the brick boundary as soon as brickFunc completes. Whereas the rayDeepBrick samples along dt, this is required for further DDA jumps at level 1.

There may be a variant of this approach which preserves the 't' value across bricks, making the deep volume sampling easier, but it must account for stepping across, up and down the tree also. I believe I experimented with this yet was unable to find a solution for rayCast that covered all scenarios. The current approach works for both deep and isosurface raytracing, and when the ray traces several side-by-side bricks, or if it has to jump across empty bricks and re-enter elsewhere.

[drmateo]

You are rigth. Thanks for your feedback