I took a closer look and I get an error indicating that the OES_standard_derivatives extension has not been enabled when the square grid is used but not when a hex grid is used. [17991:17991:1103/003327.743148:INFO:CONSOLE:3] "BJS - [00:33:27]: Error compiling effect", source: <a href="https://cdn.roll20.net/vtt/jumpgate/production/latest/totallyNotAnalytics.bundle.b79d2cd60574f04210e4.js" rel="nofollow">https://cdn.roll20.net/vtt/jumpgate/production/latest/totallyNotAnalytics.bundle.b79d2cd60574f04210e4.js</a> (3)
[17991:17991:1103/003327.746245:INFO:CONSOLE:3] "BJS - [00:33:27]: Unable to compile effect:", source: <a href="https://cdn.roll20.net/vtt/jumpgate/production/latest/totallyNotAnalytics.bundle.b79d2cd60574f04210e4.js" rel="nofollow">https://cdn.roll20.net/vtt/jumpgate/production/latest/totallyNotAnalytics.bundle.b79d2cd60574f04210e4.js</a> (3)
[17991:17991:1103/003327.747355:INFO:CONSOLE:3] "BJS - [00:33:27]: Uniforms: world, worldView, worldViewProjection, gridSize, color, opacity", source: <a href="https://cdn.roll20.net/vtt/jumpgate/production/latest/totallyNotAnalytics.bundle.b79d2cd60574f04210e4.js" rel="nofollow">https://cdn.roll20.net/vtt/jumpgate/production/latest/totallyNotAnalytics.bundle.b79d2cd60574f04210e4.js</a> (3)
[17991:17991:1103/003327.748109:INFO:CONSOLE:3] "BJS - [00:33:27]: Attributes: position, uv", source: <a href="https://cdn.roll20.net/vtt/jumpgate/production/latest/totallyNotAnalytics.bundle.b79d2cd60574f04210e4.js" rel="nofollow">https://cdn.roll20.net/vtt/jumpgate/production/latest/totallyNotAnalytics.bundle.b79d2cd60574f04210e4.js</a> (3)
[17991:17991:1103/003327.748719:INFO:CONSOLE:3] "BJS - [00:33:27]: Defines:
#define NUM_BONE_INFLUENCERS 0
#define NUM_MORPH_INFLUENCERS 0", source: <a href="https://cdn.roll20.net/vtt/jumpgate/production/latest/totallyNotAnalytics.bundle.b79d2cd60574f04210e4.js" rel="nofollow">https://cdn.roll20.net/vtt/jumpgate/production/latest/totallyNotAnalytics.bundle.b79d2cd60574f04210e4.js</a> (3)
[17991:17991:1103/003327.749297:INFO:CONSOLE:3] "BJS - [00:33:27]: Error: FRAGMENT SHADER ERROR: 0:15: 'GL_OES_standard_derivatives' : extension is disabled
�", source: <a href="https://cdn.roll20.net/vtt/jumpgate/production/latest/totallyNotAnalytics.bundle.b79d2cd60574f04210e4.js" rel="nofollow">https://cdn.roll20.net/vtt/jumpgate/production/latest/totallyNotAnalytics.bundle.b79d2cd60574f04210e4.js</a> (3)
From OES_standard_derivatives extension This extension is only available to WebGL1 contexts. In WebGL2, the functionality of this extension is available on the WebGL2 context by default. So it only needs to be enabled it on systems that only support WebGL1. If I enable the extension in the square grid shader code by adding a #extension GL_OES_standard_derivatives : enable line I can get the square grid to appear. That is when I make the following change $ diff -u7 vtt.bundle.b30cef3cc0400914a64d.js.~1~ vtt.bundle.b30cef3cc0400914a64d.js
--- vtt.bundle.b30cef3cc0400914a64d.js.~1~ 2025-11-02 23:16:03.473576000 +0000
+++ vtt.bundle.b30cef3cc0400914a64d.js 2025-11-03 00:37:09.874576000 +0000
@@ -6541,14 +6541,15 @@
}`,h6=`// Adapted from <a href="https://madebyevan.com/shaders/grid/" rel="nofollow">https://madebyevan.com/shaders/grid/</a>
precision highp float;
#define GLSLIFY 1
uniform vec2 gridSize;
uniform vec3 color;
uniform float opacity;
varying vec2 vUV;
+#extension GL_OES_standard_derivatives : enable
void main() {
// The coordinate we're looking at scaled to the grid size.
vec2 coord = vUV * vec2(gridSize.x, gridSize.y);
// Compute anti-aliased world-space grid lines
vec2 grid = abs(fract(coord - 0.5) - 0.5) / fwidth(coord);
float line = min(grid.x, grid.y);
although I have no idea if this is a proper fix.