Tiled terrain and normals

Next, problem are texture seams between terrain tile borders (expected). Did a quick smoothstep in shader between 4 textures like this:


uniform sampler2D texture_heightMap;

uniform sampler2D texture_sandMap;
uniform sampler2D texture_grassMap;
uniform sampler2D texture_gravelMap;
uniform sampler2D texture_snowMap;

void getAlbedo() {
    
    vec4 bumpData = texture2D( texture_heightMap, $UV );
    float amount = bumpData.r;
    
    vec3 sand = (smoothstep(0.01, 0.30, amount) - smoothstep(0.28, 0.31, amount)) * texture2DSRGB( texture_sandMap, $UV * 25.0 ).$CH;
    vec3 grass = (smoothstep(0.28, 0.32, amount) - smoothstep(0.35, 0.40, amount)) * texture2DSRGB( texture_grassMap, $UV * 25.0).$CH;
    vec3 gravel = (smoothstep(0.30, 0.50, amount) - smoothstep(0.40, 0.70, amount)) * texture2DSRGB( texture_gravelMap, $UV * 25.0).$CH;
    vec3 snow = (smoothstep(0.50, 0.65, amount)) * texture2DSRGB( texture_snowMap, $UV * 25.0).$CH;
    
    dAlbedo = sand + grass + gravel + snow;
}

Thought that clamp to edge will fix that. Do we have a property like clamp to model border or similar? Or any ideas how to fix this?

Clamp to edge:

Thanks a lot!