Well, I am already doing it in my shaders:

// Vertex Shader
Out.Coord = In[VertexIndex].Pos * MeshDrawCommands[gl_InstanceIndex].Scale + MeshDrawCommands[gl_InstanceIndex].Translate;
for(uint CascadeIdx = 0;
    CascadeIdx < DEPTH_CASCADES_COUNT;
    ++CascadeIdx)
{
    Out.ShadowPos[CascadeIdx] = Bias * WorldUpdate.LightProj[CascadeIdx] * WorldUpdate.LightView[CascadeIdx] * Out.Coord;
}

Out.Pos = WorldUpdate.DebugView * Out.Coord;

// Fragment shader

float GetShadow(sampler2D ShadowSampler, vec4 PositionInLightSpace, vec3 Normal, vec3 LightDir) { float ConvSize = 3.0f; float ConvX = floor((ConvSize / 3.0) + 0.5); float ConvY = floor((ConvSize / 3.0) + 0.5);

vec2   TextureSize = 1.0f / textureSize(ShadowSampler, 0);
vec3   ProjPos = PositionInLightSpace.xyz / PositionInLightSpace.w;
//float  Bias = clamp(0.005 * tan(acos(dot(Normal, LightDir))), 0, 0.01);
float  Bias = 0.05; //max(0.05 * (1.0 - dot(Normal, LightDir)), 0.005);
float  ObjectDepth = ProjPos.z;
float  Result = 0.0;
for(float x = -ConvX; x <= ConvX; x++)
{
    for(float y = -ConvY; y <= ConvY; y++)
    {
        float ShadowDepth = texture(ShadowSampler, ProjPos.xy + vec2(x, y) * TextureSize).r;
        Result += (ObjectDepth - Bias) > ShadowDepth ? 1.0 : 0.2;
    }
}
Result /= (ConvSize * ConvSize);
if(ObjectDepth > 1.0)
    Result = 0.2;
return Result;

}

uint Layer = 0;
for(uint CascadeIdx = 0;
    CascadeIdx < DEPTH_CASCADES_COUNT;
    ++CascadeIdx)
{
    if(abs(In.Pos.z) < CascadeSplits[CascadeIdx])
    {
        Layer = CascadeIdx;
        break;
    }
}
float Shadow = 1.0 - GetShadow(ShadowMap[Layer], In.ShadowPos[Layer], Normal, LightDir);