guard against issue with bumpiness in impostors

CHANGELOG.md

@@ -6,6 +6,8 @@ Note that since we don't clearly distinguish between a public and private interf
 
 ## [Unreleased]
 
+- Better guard against issue (black fringes) with bumpiness in impostors
+
 ## [v3.26.0] - 2022-12-04
 
 - Support for ``powerPreference`` webgl attribute. Add ``PluginConfig.General.PowerPreference`` and ``power-preference`` Viewer GET param.

src/mol-gl/shader/chunks/apply-light-color.glsl.ts

@@ -12,7 +12,7 @@ export const apply_light_color = `
     gl_FragColor = material;
 #else
     #ifdef bumpEnabled
-        if (uBumpFrequency > 0.0 && uBumpAmplitude > 0.0) {
+        if (uBumpFrequency > 0.0 && uBumpAmplitude > 0.0 && bumpiness > 0.0) {
             normal = perturbNormal(-vViewPosition, normal, fbm(vModelPosition * uBumpFrequency), (uBumpAmplitude * bumpiness) / uBumpFrequency);
         }
     #endif