float ao = smoothstep(0.0, 0.7, vGrassUv.y);
ao = mix(0.05, 1.0, ao);

vec3 rootColor = diffuseColor.rgb * 0.4;
vec3 tipColor = diffuseColor.rgb * 1.5;

vec3 grassColor = mix(rootColor, tipColor, vGrassUv.y);
grassColor *= ao;

float translucency = pow(vGrassUv.y, 2.0) * 0.5;
grassColor += diffuseColor.rgb * translucency;

diffuseColor.rgb = grassColor;