Question What is the correct way to calculate the depth of objects under a mesh?

I am so confused which node to use to calculate the depth under my water plane...its not clear which ones you should use to subtract to get the true distance.

My current setup is like this:



I output to base so i can just see a white fade to see if its working but it doesn't and its buggy:



What's the correct way to calculate this?

 

Maybe use the world (or maybe object, but assume world) position instead of the view position?

 

But the depth is relative to camera. It didn't work for me.

 

Hi, I think what you need is not depth (distance to camera), but vertical distance between two "points" (position.y related).

There's no cube's position information in water plane shader.

In this case, you can reconstruct the position (can be WorldSpace, NDC, ...) with scene depth (such as this thread).

This node samples the camera depth texture. (stores opaque object's depth only)


For each pixel (on water plane), this node returns the opaque scene (cube's) depth.

(Pictures are hidden in spoiler blocks, sorry that the color is terrible)

Spoiler

See, these two points have different depth.

You can convert this opaque scene (cube's) depth to position so that it's possible to calculate vertical distance.

Spoiler

"d" is the vertical distance.
You can easily get the water plane point (pixel)'s position with a Position Node.

 

The range of vertical distance depends on the position type.

If you need a more controllable range, I suggest reconstructing to "NDC space (-1..1)", rather than "WorldSpace".