Alpha mask + translucent feature not working

[lilleyse]

This is a ModelExperimental bug

Background: When a feature in a primitive become translucent we generate an opaque command and a translucent command. CPUStylingPipelineStage is responsible for rendering only opaque features in the opaque command and only translucent features in the translucent command.

The problem is that renderResources.alphaOptions.alphaMode is set to AlphaMode.BLEND and #define ALPHA_MODE_BLEND is set for both commands.

In ModelExperimentalFS.glsl this means the opaque command actually goes down the ALPHA_MODE_BLEND code path and doesn't discard alpha-mask pixels. Which leads to the artifacts in the gif below.

vec4 handleAlpha(vec3 color, float alpha)
{
    #ifdef ALPHA_MODE_MASK
    if (alpha < u_alphaCutoff) {
        discard;
    }
    return vec4(color, 1.0);
    #elif defined(ALPHA_MODE_BLEND)
    return vec4(color, alpha);
    #else // OPAQUE
    return vec4(color, 1.0);
    #endif
}

Sandcastle

N12E045_D101_S002_T001_L4_U12_R0.glb.zip