Uploaded September 2018 | Updated September 2026, 1 week ago

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In this video we'll have a look at how we can use the depth buffer to find out how much distance there is between the surface of the water and the walls of the pool behind it. Then we use that to darken the water the higher that distance is.

Info about reconstructing positions from depth buffer:
derschmale.com/2014/01/26/reconstructing-positions-from-the-depth-buffer

Beers law:
en.wikipedia.org/wiki/Beer%E2%80%93Lambert_law

Just for completeness (note I'm leaving z as negative):
float depth = texture(DEPTH_TEXTURE, SCREEN_UV).r;
depth = depth * 2.0 - 1.0;
float z = -PROJECTION_MATRIX[3][2] / (depth + PROJECTION_MATRIX[2][2]);
float x = (SCREEN_UV.x * 2.0 - 1.0) * z / PROJECTION_MATRIX[0][0];
float y = (SCREEN_UV.y * 2.0 - 1.0) * z / PROJECTION_MATRIX[1][1];

or alternatively:
float depth = texture(DEPTH_TEXTURE, SCREEN_UV).r;
vec4 unproject = INV_PROJECTION_MATRIX * vec4(SCREEN_UV * 2.0 - 1.0, depth * 2.0 - 1.0, 1.0);
vec3 view_vertex = unproject.xyz / unproject.w;

Source code on github:
github.com/BastiaanOlij/shader_tutorial

Playlist:
youtube.com/watch?v=xoyk_A0RSpI&list=PLhqJJNjsQ7KHqNMYmTwtsYTeTrqrRP_fP

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