countingView module

Builds a camera view that counts, per pixel, how many fragments satisfy a depth predicate, and colours the count. overdraw and zfighting are both instances of it; a diagnostic of your own is one more.

local CountingView = require("@builtin::systems.renderDiagnostics.countingView")

return CountingView.new({
    view = "myView",              -- the name `capture pass=myView` selects
    geometry = "@geometry.all",   -- which drawables are counted
    depthCompare = "always",      -- which of their fragments count
    levels = 16,                  -- counts that fit before the sum saturates
    mapShader = asset.resolve("~.shaders.myViewMap", "shader"),
})

The return value is a .renderFeature module — render enqueues the view's passes, teardown releases them — so a feature's whole init.luau is this one call. Register the name separately with renderer.captureView.register so capture pass=<name> resolves to it.

The two knobs that decide the question

depthCompare runs against the scene depth the frame already resolved:

• "always" counts every fragment the rasterizer produced, hidden ones included — the shading work a pixel costs.
• "lessEqual" counts only fragments reaching the winning depth — one per pixel, unless surfaces are close enough that the depth buffer cannot tell them apart.

geometry narrows what is counted: "@geometry.all", "@geometry.opaque" or "@geometry.transparent".

Reading the count

levels is how many counts fit before the accumulated sum saturates at 1.0, so a view's open-ended "this many or more" band belongs at or below that number.

mapShader is a @domain: post-process .shader asset declaring fn zero_count_color(n: i32) -> vec3<f32> — the view's reading of the decoded count, 0 where nothing was counted — over the shared decode body:

// @domain: post-process

fn zero_count_color(n: i32) -> vec3<f32> {
    ...
}

#include "~.shaders.countMap"

Flat, nameable bands read better from a still than a continuous ramp: the question is which band a region falls in, not how bright it is.