 
 uniform samplerCube RadianceEnvironment;
 uniform sampler3D SceneOpacityVoxel;
+uniform usampler3D PageMask;
 // maps world coords in bounds to the -0.5 .. +0.5 range
 uniform mat4 WorldToVoxelSpace;
 uniform int MaxMipmapLevel;

*/

#include <common.h>
#include "pass/gbuffer.h"
#include <brdf.h>


    float sampleDiameter = max(minDiameter, ConeAngleRatio * dist);
    float sampleLOD   = log2(sampleDiameter * gridDim);
    vec3 samplePos    = Origin + Direction * dist;
    // front to back accumulation
    // float mask = float(texture(PageMask, samplePos).r) / USE_PAGE_MARKER;
    vec4 sampleValue  = textureLod(SceneOpacityVoxel, samplePos, sampleLOD);
    accum += sampleValue * (1.0 - accum.w);
    dist += sampleDiameter;
