Unified perspective near-plane fade. isOrthoInt is the int ortho flag of the
draw — every caller passes isOrthoProjectionTSL (or a var holding it).
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.
isOrthoIntis the int ortho flag of the draw — every caller passes isOrthoProjectionTSL (or a var holding it). 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.