HLSL Pixelshader Texture Blending

//input.Int is the interpolated position in object space, as opposed to the clip space in SV_Position
float3 pos = input.Int.xyz;

//load normal map and calculate missing component
float3 n;
n.xz = (g_Normal.Sample(samAnisotropic, input.Tex).xy * 2 - 1);
n.y = sqrt(1 - min(1.0f, n.x * n.x + n.z * n.z));
n = normalize(n);

//calculate slope and height for texture blending
float slope = 1 - n.y;
float height = (sqrt(max(0, pos.x * pos.x + pos.y * pos.y + pos.z * pos.z)) - g_TerrainScaling.x)/(g_TerrainScaling.y);

//alphas for texture blending
float a1 = smoothstep(smoothstep(smoothstep(smoothstep(smoothstep(slope + 0.15f)))));				//dirt
float a2 = smoothstep(smoothstep(smoothstep(smoothstep(height + 0.1f))));					//rock
float a3 = smoothstep(smoothstep(smoothstep(smoothstep(smoothstep(smoothstep(height - 0.1f))))));		//snow
float a4 = smoothstep(smoothstep(abs(pos.y/g_TerrainScaling.x) + 0.45f));					//desert



//load different textures
float3 grass = t_Grass.Sample(samAnisotropic, tex * 50).xyz;
float3 dirt = t_Dirt.Sample(samAnisotropic, tex * 50).xyz;
float3 rock = t_Rock.Sample(samAnisotropic, tex * 50).xyz;
float3 sand = t_Sand.Sample(samAnisotropic, tex * 50).xyz;
float3 snow = t_Snow.Sample(samAnisotropic, tex * 50).xyz;
float3 water = t_Water.Sample(samAnisotropic, tex * 25).xyz;



d = (((grass * (1 - a1) + a1 * dirt) * (a4) + (1 - a4) * sand) * (1 - a2) + a2 * rock) * (1 - a3) + a3 * snow;   //(1 - a3) * ((1 - a2) * ((1 - a1) * grass + dirt * a1) + snow * a2) + rock * a3;