Tuesday, 23 April 2013

Day 3 with my shooter game

I had the chance last weekend to spent some time on the game.
I removed the jump button and instead I am using one button for moving and jumping and the other for shooting.

Also did some work on the visuals (excuse my artwork for the buttons :-P) to add some colour and make it look bit polished.

Saturday, 13 April 2013

Beware Of The Mini UFO

Today I had some time to catch up with the game and now I have a "playable" prototype version.
I've added one type of enemy AI for now, health , basic waves logic and some scoring to make it look like a serious project :-P
Still long way to go:

Next steps is to optimise this version and do some game play design

Friday, 12 April 2013

Light calculations inside Unity's CG shader

Unity provides Built-in values that can be used to do the lighting calculations inside CG shaders.
However, the documentation seems to be outdated because when i tried using the values:
 _ModelLightColor[0], _ObjectSpaceLightPos[0]
I got undefined variable error.

After digging into UnityCG.cginc I found unity_LightPosition[0] &unity_LightColor[0] variables which did the trick.

Here is an example of a basic per-vertex diffuse lighting Shader that accepts a texture and an ambient color inputs and adds one light calculations:
Shader "Custom/Per-Vertex diffuse" {
      Properties {
        _MainTex ("Texture 1", 2D) = "white" {}
        _Ambient("Ambient Color",Color) = (0.3,0.3,0.3,1)
      SubShader {
      Tags { "RenderType"="Opaque"}
      Pass {
           Tags { "LightMode" = "Vertex" }//otherwise no light related values will be filled
           #pragma vertex vert
           #pragma fragment frag
           #include "UnityCG.cginc"
           sampler2D _MainTex;
           fixed4 _Ambient;
           half4 _MainTex_ST;
           struct v2f{
               fixed4 position: POSITION;
               half2 uv_MainTex:TEXCOORD0;
               fixed4 color: COLOR;
           v2f vert (appdata_base ab) {
               v2f o;
               o.position = mul(UNITY_MATRIX_MVP,ab.vertex);
               o.uv_MainTex = TRANSFORM_TEX(ab.texcoord.xy , _MainTex);
               // per vertex light calc
               fixed3 lightDirection;
               fixed attenuation;
               // add diffuse
               if(unity_LightPosition[0].w == 0.0)//directional light
                  attenuation = 2;
                  lightDirection = normalize(mul(unity_LightPosition[0],UNITY_MATRIX_IT_MV).xyz);
               else// point or spot light
                  lightDirection = normalize(mul(unity_LightPosition[0],UNITY_MATRIX_IT_MV).xyz - ab.vertex.xyz);
                  attenuation = 1.0/(length(mul(unity_LightPosition[0],UNITY_MATRIX_IT_MV).xyz - ab.vertex.xyz)) * 0.5;
               fixed3 normalDirction = normalize(ab.normal);
               fixed3 diffuseLight =  unity_LightColor[0].xyz * max(dot(normalDirction,lightDirection),0);
               // combine the lights (diffuse + ambient)
               o.color.xyz = diffuseLight * attenuation + _Ambient.xyz;
               return o;
           fixed4 frag(v2f i):COLOR{
              fixed4 c = tex2D(_MainTex, i.uv_MainTex);   
              return  c * i.color;
Fallback "Mobile/Diffuse"


To learn about the math of differnt types of lighting I recommend Nvidia's Tutorial for CG shaders

Sunday, 7 April 2013

Fill Shader for Unity

I wrote a simple shader that can be used to "fill" a 3d model with a color gradient and texture by feeding a fill input.

The shader has two passes:
  • One pass to draw the border
  • The other uses the color and texture inputs + fill parameter that I check against the UV coordinates and set alpha accordingly

The following is the result for Y-axis UV "fill"