Value of depth in ShaderPass with depth

Questions
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1

Hi,

I’m trying to use the depth (distance from camera) value in a fragment shader use in post processing. I based my code on this example.

I have an orthographic camera and a scene that’s 300x300x300, with a sphere of diameter 200 right in the middle, and the camera looking at it. After tweaking things a bit, I can render the depth to the screen.

depth of sphere
depth of sphere1144×882 13.6 KB

here’s the link: codepen link

While it works, there’s a few things I don’t understand:

  • What does “depth” represent exactly? I first assumed it was the distance to the camera plane, but I have to multiply that value by 1000000 to get something meaningful. And moreover if I set the camera.near to 0, the depth won’t work at all, which I don’t understand.
  • What is the dimension of the depth texture? Should that be the same size (in pixels) as the canvas rendering the scene?

Thanks in advance!

2

I’ve just realized the fragment shader can be simplified to something like this:

        varying vec2 vUv;
        uniform sampler2D tDepth;

        void main() {
            float depth = texture2D( tDepth, vUv ).x * 15.0;
            gl_FragColor.rgb = 1.0 - vec3( depth);
            gl_FragColor.a = 1.0;
        }
3

Ok, I’ve figured it out. The value of depth ranges from 0 (near plane) to 1 (far plane). I had a typo in my code and the far plane was much further than expected (x10).

(codepen updated with the working version)