I have some basic shapes in the background of a scene that represent a small city. There is a stage where the scene becomes a nights scene. I would like to have the city come to life at night with some lights.

I know that I can use a texture with emissions to achieve this effect, but the texture is extremely repetitive and the lack of variation stands out. It is a bit boring, but works relatively well.

As I am trying to learn shaders, I thought it might be a good project to attempt. The shader just divides the UV and then draws a base color or a window color. It is also more random and lights could be switched on or off over time.

enter image description here

So far so good, but there is a problem the moment the camera moves a bit away. enter image description here enter image description here

It looks like there is some strolling or banding effect. The "lights" seem to flicker a lot. I think I understand why this is happening. Maybe because the pixels visible at that instant, that determine if its a window or wall just ends up all being walls ? Or the window is smaller than 1 pixel ?

Like I said, I am just starting with shaders and have no real clue what I am doing. Can this be done with a simple shader ?

Here is what I have so far:

Shader "Custom/EmeraldCityLights"
        _Color ("Color", Color) = (1,1,1,1)
        _MainTex ("Albedo (RGB)", 2D) = "white" {}  // These will not be used 
        _Glossiness ("Smoothness", Range(0,1)) = 0.5// These will not be used 
        _Metallic ("Metallic", Range(0,1)) = 0.0    // These will not be used 
        Tags { "RenderType"="Opaque" }
        LOD 200

        // Physically based Standard lighting model, and enable shadows on all light types
        #pragma surface surf Standard fullforwardshadows

        // Use shader model 3.0 target, to get nicer looking lighting
        #pragma target 3.0

        sampler2D _MainTex;

        struct Input
            float2 uv_MainTex;
            float3 worldNormal;

        half _Glossiness;
        half _Metallic;
        fixed4 _Color;

        // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
        // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
        // #pragma instancing_options assumeuniformscaling
            // put more per-instance properties here

        float random2(float2 uv)
            return  frac(sin(uv.x * 12.11 + uv.y * 88.44) * 4497.1546);

        void surf (Input IN, inout SurfaceOutputStandard o)
            // Albedo comes from a texture tinted by color
            //fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
            half4 col = half4(0, .1, 0, 1.0);  // Building's base color
            half4 windowW = half4(1, 1, 1, 1.0);  // white window color
            half4 windowO = half4(.05, .05 ,.05, 1.0); // Windows that have no lights behind them (off)
            half4 windowY = half4(1, 1, .1, 1.0); // Yellow windows
            float2 t = IN.uv_MainTex;  // Get the UV x,y of this pixel

            float2 gt = float2(t.x * 12, t.y*20.5);  // Multiply to repeat the pattern. 12 windows by 20.5
            float2 gv = frac(gt);       //Use the frac part to draw this window.
            float2 windowID = float2((int)gt.x, (int)gt.y);  // the integer part is the windows index.

            float rnd = random2(windowID);  // get a random number based on this window's ID. All the pixels in this window will be the same color.

            fixed4 c =  lerp(lerp(windowW,windowY,rnd*1.429), windowO, step(0.7,rnd)) * 13.0; // if the random number is less than 0.7, the light is on.
                                                                                              // if the light is on, then lerp from white to yellow based on the random number.
            c = lerp(col, c, step(abs(IN.worldNormal.g), 0));   // Get the pixel's world normal. if the normal points up or down, make it the building's base color
            c = lerp(col, c, step(0.15, gv.x)); // if this pixel is on the left edge of the window, make it the building's base color
            c = lerp(c, col, step(0.85, gv.x));// if this pixel is on the right edge of the window, make it the building's base color
            c = lerp(c, col, step(gv.y - .25,0.25 )); // if its at the top or bottom, make it the building's base color
             o.Albedo = c.rgb;

            // not used yet
            //o.Metallic = _Metallic;
            //o.Smoothness = _Glossiness;
            //o.Alpha = c.a;
    FallBack "Diffuse"
  • 2
    \$\begingroup\$ If you're seeking feedback on a shader, it's helpful to post the entire shader (rather than just some of the functions) so we can try it out. \$\endgroup\$
    – Kevin
    Nov 3 at 2:34
  • \$\begingroup\$ @Kevin Thanks for the tip. I updated the code block. \$\endgroup\$ Nov 3 at 7:16


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