in fragment shader
fixed4 frag (v2f i) : SV_Target { fixed4 col = float4(1,0,0,1); col = lerp(col,float4(0,1,0,1),smoothstep(0,0.333,i.uv.x)); col = lerp(col,float4(0,0,1,1),smoothstep(0.333,0.666,i.uv.x)); col = lerp(col,float4(1,0,0,1),smoothstep(0.666,1.0,i.uv.x)); return col; }