_Projector, Projector shader and CG

Hi all.

Trying to improve the visual quality of our projectors, I wanted to modify the shader we use for the projectors material.

This is what we and probably most people are using:

Code (csharp):

1. Shader "Projector/Projector Multiply"
2. {
3.     Properties
4.     {
5.         _Color ("Main Colour", Color) = (1,1,1,0)
6.         _ShadowTex ("Cookie", 2D) = "gray" { TexGen ObjectLinear }
7.     }
8.  
9.     Subshader
10.     {
11.         Tags { "RenderType"="Transparent"  "Queue"="Transparent+100"}
12.         Pass
13.         {
14.             ZWrite Off
15.             Offset -1, -1
16.  
17.             Fog { Mode Off }
18.            
19.             //AlphaTest Greater .1
20.             AlphaTest Less 1
21.             ColorMask RGB
22.             Blend One SrcAlpha
23.  
24.             SetTexture [_ShadowTex]
25.             {
26.                 constantColor [_Color]
27.                 combine texture * constant, One - texture
28.                 Matrix [_Projector]
29.             }
30.         }
31.     }
32. }
33.  

We slightly modified it so that it can take a color and removed the falloff texture, but that's pretty much what you'll find in the Projectors package BlobShadow prefab shader.





Since I want way better control about the way this is all rendered, I wanted to move it to CG code. My puny and failed attempt at simply reproducing what the fixed function shader was doing looks like this:

Code (csharp):

1. Shader "Projector/Projector Multiply"
2. {
3.     Properties
4.     {
5.         _Color ("Main Colour", Color) = (1,1,1,0)
6.         _ShadowTex ("Cookie", 2D) = "gray" { TexGen ObjectLinear }
7.     }
8.  
9.     Subshader
10.     {
11.         Tags { "RenderType"="Transparent"  "Queue"="Transparent+100"}
12.         Pass
13.         {
14.             ZWrite Off
15.             Offset -1, -1
16.  
17.             Fog { Mode Off }
18.            
19.             //AlphaTest Greater .1
20.             AlphaTest Less 1
21.             ColorMask RGB
22.             Blend One SrcAlpha
23. CGPROGRAM
24. #pragma vertex vert
25. #pragma fragment frag
26. #pragma fragmentoption ARB_fog_exp2
27. #pragma fragmentoption ARB_precision_hint_fastest
28. #include "UnityCG.cginc"
29.  
30. struct v2f
31. {
32.     float4 pos : SV_POSITION;
33.     float2  uv_Main     : TEXCOORD0;
34. };
35.  
36. sampler2D _ShadowTex;
37. float4 _Color;
38. float4x4 _Projector;
39.  
40. v2f vert(appdata_tan v)
41. {
42.     v2f o;
43.     o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
44.     o.uv_Main = mul (_Projector, v.texcoord).xy;
45.     return o;
46. }
47.  
48. half4 frag (v2f i) : COLOR
49. {
50.     half4 tex = tex2D(_ShadowTex, i.uv_Main) * _Color;
51.     tex.a = 1-tex.a;
52.     return tex;
53. }
54. ENDCG
55.  
56.         }
57.     }
58. }
59.  

This doesn't work, it looks like the projection is being done wrong, as it seems to take only a very little part of the texture I'm passing in:



(I didn't use the same texture since the other one was simply giving invisible results, whereas this one shows a little gradient on the right coming from the texture, God knows from what part of it though)
(The receiving geometry in the back is a Terrain in both cases)

Anyone knows projectors in great details, someone from Unity who worked on it? Someone like, oh I don't knooow, let's saaaaay, Aras?

 

Still in need of an answer for that.

Also, I'd like to be able to control the projection's transparency by the main color's alpha channel, with the old shader everyone uses.
If I do something like

Code (csharp):

1. combine texture * constant, One - texture * constant

and set the main color's alpha to 0.5 (128), all I get is



instead of



if I set the main color's alpha back to 1, which isn't the result I was expecting.

Thanks for any help. At all. Please.

 

Concerning the ability to fade a projector in transparency, this shader works:

Code (csharp):

1.  
2.     Subshader
3.     {
4.         Tags { "RenderType"="Transparent" "Queue"="Transparent-100" }
5.         Pass
6.         {
7.             ZWrite Off
8.             Fog { Mode Off }
9.             ColorMask RGB
10.             Blend SrcAlpha OneMinusSrcAlpha
11.             SetTexture [_ShadowTex]
12.             {
13.                 constantColor [_Color]
14.                 combine texture * constant, texture * constant
15.                 Matrix [_Projector]
16.             }
17.         }
18.     }

But I'd really rather do those things in CG.

Thanks!

 

Got it:

Code (csharp):

1. Shader "Projector/Projector MultiplyCG"
2. {
3.     Properties
4.     {
5.         _Color ("Main Colour", Color) = (1,1,1,0)
6.         _ShadowTex ("Cookie", 2D) = "gray" { TexGen ObjectLinear }
7.     }
8.  
9.     Subshader
10.     {
11.         Tags { "RenderType"="Transparent"  "Queue"="Transparent+100"}
12.         Pass
13.         {
14.             ZWrite Off
15.             Offset -1, -1
16.  
17.             Fog { Mode Off }
18.            
19.             AlphaTest Less 1
20.             ColorMask RGB
21.             Blend One SrcAlpha
22. CGPROGRAM
23. #pragma vertex vert
24. #pragma fragment frag
25. #pragma fragmentoption ARB_fog_exp2
26. #pragma fragmentoption ARB_precision_hint_fastest
27. #include "UnityCG.cginc"
28.  
29. struct v2f
30. {
31.     float4 pos : SV_POSITION;
32.     float[COLOR="red"]4[/COLOR] uv_Main     : TEXCOORD0;
33. };
34.  
35. sampler2D _ShadowTex;
36. float4 _Color;
37. float4x4 _Projector;
38.  
39. v2f vert(appdata_tan v)
40. {
41.     v2f o;
42.     o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
43.     o.uv_Main = [COLOR="red"]mul (_Projector, v.vertex);[/COLOR]
44.     return o;
45. }
46.  
47. half4 frag (v2f i) : COLOR
48. {
49.     half4 tex = [COLOR="red"]tex2Dproj[/COLOR](_ShadowTex, [COLOR="red"]UNITY_PROJ_COORD(i.uv_Main)[/COLOR]) * _Color;
50.     tex.a = 1-tex.a;
51.     return tex;
52. }
53. ENDCG
54.         }
55.     }
56. }
57.  

Serves me right for completely overlooking TexGen ObjectLinear in the texture declaration

We now have a CG version of the projector shader to which we can do more easily some nasty though cool and expensive things!

All my thanks to Aras

 

Thanks

 

I am looking to make my own projector shader. The code posted above throws many errors in Unity 4. Are there any examples or working unity cg shaders for projectors out there?

 

This might work with Unity4 (not sure): http://en.wikibooks.org/wiki/Cg_Programming/Unity/Projectors
Let me know if it doesn't.

 

Many thanks, Martin! It compiles, though it has some issues with flickering and applying the blob shadow to objects that are not in the projectors FOV. I will tinker around and see if I can get it working correctly before posting again.

 

I am thankfull from the deep of my heart, this code saved my life!

The code works, just remove any tag between "[ ]" like "[Color = "red"]" this is probably due to the code editor in here...