Unified perspective near-plane fade (runtime-uniform variant, for
the point/gsplat graphs whose ortho flag is the uIsOrtho uniform).
Mirrors GLSL perspectiveNearFade in glsl-lib.ts: perspective =
0.0 behind the camera, smoothstep across [nearCull, 2*nearCull];
ortho = 1.0 always (NDC clipping is the sole cull authority).
Callers reject the vertex when the result < 0.01 and multiply the
surviving amplitude/alpha/brightness by it.
Unified perspective near-plane fade (runtime-uniform variant, for the point/gsplat graphs whose ortho flag is the
uIsOrthouniform). Mirrors GLSLperspectiveNearFadein glsl-lib.ts: perspective = 0.0 behind the camera, smoothstep across [nearCull, 2*nearCull]; ortho = 1.0 always (NDC clipping is the sole cull authority). Callers reject the vertex when the result < 0.01 and multiply the surviving amplitude/alpha/brightness by it.