HdStorm Mesh Wires drawing issue in USD 24.05 on MacOS

Community Hydra
1

Hi, When upgrading from USD 23.11 to USD 24.05, we got a mesh wires drawing issue on MacOS, it seems to be a regression of computing of edge opacity in Storm shader, it caused all edge pixels to be discarded, nothing was drawn under wireframe mode, no such issue on Windows & Linux.

// line 265 “meshWire.glslfx”
vec4 ApplyEdgeColor(vec4 Cfill, vec4 patchCoord)
{
float p = GetEdgeOpacity();
if (p < 0.5) discard;
vec4 wireColor = GetWireframeColor();
// If wireColor is unset (zero), ignore it altogether
Cfill.rgb = mix(Cfill.rgb, wireColor.rgb, wireColor.a);
return ApplyFinalEdgeOpacity(Cfill);
}

Here’s how Edge Opacity is computed, anyone know any changes related to this?

// line 82 “meshWire.glslfx”

// Returns the distance of the current fragment (in viewport pixel units) from
// the nearest edge.
float GetMinEdgeDistance()
{
// Hide triangle edges by adding edge mask.
vec3 param = GetEdgeCoord() + GetPrimitiveEdgeMask();
vec3 edgeDistance = max(vec3(0.0), param / fwidth(param));
return min(edgeDistance.x,
min(edgeDistance.y,
edgeDistance.z));
}

// Use edge distance to compute a smooth opacity falloff for good looking edges.
float GetEdgeFalloff(float d) {
return exp2(-4 * d * d);
}

float GetEdgeOpacity() {
return GetEdgeFalloff(GetMinEdgeDistance());
}

Thanks,
Keli