Evaluate the ambient probe outside of the loop

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Lighting/Volumetrics/Resources/VolumetricLighting.compute

     float t0 = ray.strataDirInvViewZ * z0; // Convert view space Z to distance along the stratified ray
     float de = rcp(VBUFFER_SLICE_COUNT);   // Log-encoded distance between slices
 
+    // The contribution of the ambient probe does not depend on the position,
+    // only on the direction and the length of the interval.
+    float3 probeInScatteredRadiance = EvaluateLightProbe(GetPreconvolvedAmbientProbe(), ray.centerDirWS);
+
     float3 totalRadiance = 0;
     float  opticalDepth  = 0;
 
         float phase = IsotropicPhaseFunction();
     #endif
 
-        // Sample the light probe.
-        float3 probeRadiance = EvaluateLightProbe(GetPreconvolvedAmbientProbe(), ray.centerDirWS) * TransmittanceIntegralHomogeneousMedium(extinction, dt);
-
+        // Integrate the contribution of the probe over the interval.
+        float3 probeRadiance = probeInScatteredRadiance * TransmittanceIntegralHomogeneousMedium(extinction, dt);
+
         totalRadiance += transmittance * scattering * (phase * blendedRadiance + probeRadiance);
 
         // Compute the optical depth up to the center of the interval.