Double Paraboloid Seams

Question

Double Paraboloid Seams

I implemented double paraboloid shadows for point lights. The goal was to reduce the number of shadow passes. GLES3.0 is also a goal, so there is no multi-level rendering. Shadows work, and in fact the quality is not bad. There is one problem. I store both hemisphere maps in the same atlas during a shadow passage. During the passage of lighting, I take a sample from this atlas, from the corresponding part based on the direction (forward or backward). When the shadow crosses both cards there is a white seam in the middle. I tried to change the FBO texture filter mode, also changed the wrapping mode, but nothing helps. Here is a screenshot:

and this is a double shadow mapping:

- , , . .

GLSL :

float Shadow(vec3 viewPos,vec3 lightViewPos,vec3 viewNormal,float bias)
{
 vec3 vPosDP = vec3(u_lightViewMatrix * v_worldPosition); 
 float fLength = length(vPosDP);
 vPosDP /= fLength;
 lightViewPos = (u_viewMatrix * vec4(lightViewPos,1.0)).xyz;
 vec3 L = normalize(lightViewPos - viewPos);
 float NdotL = saturate(dot(L, viewNormal));
 bias =  max(0.01 *(1.0 - NdotL), bias); 
 float fDPDepth;
 float fSceneDepth;

 if(vPosDP.z >=  0.0)//one side
 {       
    vec2 vTexFront;
    vTexFront.x =  ((vPosDP.x /  (1.0 + vPosDP.z))  * 0.25  + 0.25 ); 
    vTexFront.y =  ((vPosDP.y /  (1.0 + vPosDP.z))  * 0.5  + 0.5  );     
    fSceneDepth = (fLength - u_nearFarPlanes.x) / (u_nearFarPlanes.y - u_nearFarPlanes.x);
    fDPDepth =   texture(u_shadowMap, vec3(vTexFront,fSceneDepth - bias));            
 }
 else //another side
 {

    vec2 vTexBack;
    vTexBack.x =  ((vPosDP.x /  (1.0 - vPosDP.z)) * 0.25  + 0.75); 
    vTexBack.y =  ((vPosDP.y /  (1.0 - vPosDP.z)) * 0.5  + 0.5); 

    fSceneDepth = (fLength - u_nearFarPlanes.x) / (u_nearFarPlanes.y - u_nearFarPlanes.x);

    fDPDepth =   texture(u_shadowMap, vec3(vTexBack,fSceneDepth - bias)); 

  }
return  fDPDepth;