Transparent shader receive shadows

Hi Guys,

I am looking for Transparent shader which receives shadows! This is for Unity 5.

I need to hide geometry, which has visible shadows from other objects.

Thank you

 

Oops, nobody can code shaders here? I guess wrong community

 

This should work:

Code (CSharp):

1. Shader "Custom/TransparentShadowCollector"
2. {
3.     Properties
4.     {
5.         _ShadowIntensity ("Shadow Intensity", Range (0, 1)) = 0.6
6.     }
7.  
8.  
9.     SubShader
10.     {
11.  
12.         Tags {"Queue"="AlphaTest" }
13.  
14.         Pass
15.         {
16.             Tags {"LightMode" = "ForwardBase" }
17.             Cull Back
18.             Blend SrcAlpha OneMinusSrcAlpha
19.             CGPROGRAM
20.             #pragma vertex vert
21.             #pragma fragment frag
22.             #pragma multi_compile_fwdbase
23.  
24.             #include "UnityCG.cginc"
25.             #include "AutoLight.cginc"
26.             uniform float _ShadowIntensity;
27.  
28.             struct v2f
29.             {
30.                 float4 pos : SV_POSITION;
31.                 LIGHTING_COORDS(0,1)
32.             };
33.             v2f vert(appdata_base v)
34.             {
35.                 v2f o;
36.                 o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
37.                 TRANSFER_VERTEX_TO_FRAGMENT(o);
38.                
39.                 return o;
40.             }
41.             fixed4 frag(v2f i) : COLOR
42.             {
43.                 float attenuation = LIGHT_ATTENUATION(i);
44.                 return fixed4(0,0,0,(1-attenuation)*_ShadowIntensity);
45.             }
46.             ENDCG
47.         }
48.  
49.     }
50.     Fallback "VertexLit"
51. }

 

Thanks it works ... 90% .. I am just wondering, why the shadow is also on wrong side of the object. There is a light going from the left... and it shouldnt go through the whole 3d object. Also could you add main color into it?

(the table has shadow off, because the painting has its own shadow.)

image:
https://dl.dropboxusercontent.com/u/39935592/Echo_shader.jpg

 

Could that shadow be caused by that figure standing there?

A transparent shadow receiving object can be difficult sometimes to allow for all cases.

Here's two to try, first is the same but with a main color:

Code (CSharp):

1. Shader "Custom/TransparentShadowCollector"
2. {
3.     Properties
4.     {
5.         _Color ("Main Color", Color) = (1,1,1,.5)
6.         _ShadowIntensity ("Shadow Intensity", Range (0, 1)) = 0.6
7.     }
8.     SubShader
9.     {
10.         Tags {"Queue"="AlphaTest" }
11.         Pass
12.         {
13.             Tags {"LightMode" = "ForwardBase" }
14.             Cull Back
15.             Blend SrcAlpha OneMinusSrcAlpha
16.             CGPROGRAM
17.             #pragma vertex vert
18.             #pragma fragment frag
19.             #pragma multi_compile_fwdbase
20.             #include "UnityCG.cginc"
21.             #include "AutoLight.cginc"
22.             uniform fixed4  _Color;
23.             uniform float _ShadowIntensity;
24.             struct v2f
25.             {
26.                 float4 pos : SV_POSITION;
27.                 LIGHTING_COORDS(0,1)
28.             };
29.             v2f vert(appdata_base v)
30.             {
31.                 v2f o;
32.                 o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
33.                 TRANSFER_VERTEX_TO_FRAGMENT(o);
34.              
35.                 return o;
36.             }
37.             fixed4 frag(v2f i) : COLOR
38.             {
39.                 float attenuation = LIGHT_ATTENUATION(i);
40.                 return fixed4(0,0,0,(1-attenuation)*_ShadowIntensity) * _Color;
41.             }
42.             ENDCG
43.         }
44.     }
45.     Fallback "VertexLit"
46. }

This is the same but is at a different render queue which can sometimes get better transparency results, but you might have some depth sorting issues:

Code (CSharp):

1. Shader "Custom/TransparentShadowCollector"
2. {
3.     Properties
4.     {
5.         _Color ("Main Color", Color) = (1,1,1,.5)
6.         _ShadowIntensity ("Shadow Intensity", Range (0, 1)) = 0.6
7.     }
8.  
9.  
10.     SubShader
11.     {
12.  
13.         Tags {"Queue"="Geometry" }
14.  
15.         Pass
16.         {
17.             Tags {"LightMode" = "ForwardBase" }
18.             Cull Back
19.             Blend SrcAlpha OneMinusSrcAlpha
20.             CGPROGRAM
21.             #pragma vertex vert
22.             #pragma fragment frag
23.             #pragma multi_compile_fwdbase
24.  
25.             #include "UnityCG.cginc"
26.             #include "AutoLight.cginc"
27.             uniform fixed4  _Color;
28.             uniform float _ShadowIntensity;
29.  
30.             struct v2f
31.             {
32.                 float4 pos : SV_POSITION;
33.                 LIGHTING_COORDS(0,1)
34.             };
35.             v2f vert(appdata_base v)
36.             {
37.                 v2f o;
38.                 o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
39.                 TRANSFER_VERTEX_TO_FRAGMENT(o);
40.              
41.                 return o;
42.             }
43.             fixed4 frag(v2f i) : COLOR
44.             {
45.                 float attenuation = LIGHT_ATTENUATION(i);
46.                 return fixed4(0,0,0,(1-attenuation)*_ShadowIntensity) * _Color;
47.             }
48.             ENDCG
49.         }
50.  
51.     }
52.     Fallback "VertexLit"
53. }

 

Eek, sorry, that should + _Color not * _Color.

 

Thank you for the main color.

They both does same thing... no difference here.

Yes, the person needs to stay there to show how it works.
The table (3D object) should block the cast shadow as well. So only visible shadow from the character should be on top of the table. Not underneath, not on the side.

: Now we have matte shader receiving shadows, which is cool! Correct. But the shadows arent blocked by the 3d objects as well.

 

I don't understand why you don't use shadows only property of mesh renderer? Why do you need a shader?

 

Because it cast shadows only, not receives shadows.

 

by changing * to + all shadows and matte is gone. So I keep * (46th line)

 

Is there a way to have that hidden geometry occlude Indy??

 

For the record, it's working, you have just to set the alpha of the main color to 0.
Wonderful shader, thank you so much Echo4papa !

 

No problem.

 

@echo4papa This works with directional lights but not spot lights...do you know how I can make it work with spot lights?

 

Trawling the web for an answer to this problem, i have found this magnificent shader from @Farfarer on https://forum.unity3d.com/threads/cutout-with-soft-edge-cutout-bumped-specular.150145/

Works like a treat on unity 5.5.2f1.

kudos Farfarer, thank you!

 

I think the second shader from post number 5 is working best. But is there a way to add a texture color to the shadow?

 

Hi there, I tried the two last shaders to get a working shadow catcher when using Kudan for Unity, building for the Android platform. But alas, I see no shadow in the resulting app. I do have a shadow showing in the Unity viewport.

Any ideas?

 

@echo4papa
@paleajed
@Klaus-Eiperle
Hello, do I understand correctly that the subject of the question (and answers) is something in 3D graphics called as matte shadow?

I run into great matte shader from Unity guy Keigiro Takahashi, which also allows to adjust the color and transparency of the shadows: https://github.com/keijiro/ShadowDrawer

It has however the drawback probably common for all similar shaders - it does not work against skyboxes - only against the solid color or another object (plane - floor, wall). Unfortunately it seems to be caused by Unity design itself :-(

Does anybody know if Unity addressed this issue in the latest versions (2017.1 or 2)?
Such feature is imho very useful for things like product visualization or AR and I really miss it...

 

Yes, it would be very useful to have a shader like this that works with skyboxes. AFAIK 2017.2 does not address this.

 

Hmm so a "solution" could be to make a big inside-out sphere around your scene with the skybox on it? not the best though..

 

2017.3 and the new HD Render pipeline does semi-transparent shadow receiving/casting by default. Right now you have to add the scriptable render loop assets to your project though from the git.

 

The first code doesn't work... renders just black plane, nothing more. What can be wrong?

 

Working on an AR project where we want to have the floors of our scenes be semi-transparent... some parts fully opaque fade to complete video background as well. At first I was struggling to get the floor to receive shadows, but in this thread, I saw the suggestion to use the Alpha-Test queue and after setting the render queue to 2500, the mesh receives shadows!

However, there appears to be a big difference between DirectX 11 and Metal platforms: on Metal, the alpha of the fragment appears to effect the strength of the shadow... if the alpha is zero, you won't see ANY shadow at all... if alpha is .5, you see a half-way faded shadow, etc.

On Windows (DirectX 11) the shadows show on all fragments, which is the effect I want so that the scenery can cast shadows on the cg floor as well as the real-world surface that the scene is placed on.

I realize its a bit hack-y that putting the transparent shader on 2500 works to begin with, but I wonder if anyone can offer any suggestions that could make the shadows work regardless of the frag's alpha on Metal?

 

I know this is an old thread, but I have problems when building for Windows.

I have used this shader for quite some time and it works perfectly in the editor and on Android devices. But when building the same project for Windows, there are no shadows :-(

What should I do to get this shader work in Windows?

EDIT:
====
To answer my own question : The shader works just fine if the quality settings in Unity is set to Good or above. On Android, Unity selects the default level (which is set to Good), but in Windows Unity ignores the assigned default setting and instead selects the lowest available option (Fastest) which doesn't allow shadows.

This of course make perfect sense, who knows - the game that runs perfectly fine on an Android device may overload my Threadripper 3960x/120GB/RTX2080Ti...

I had to disable the Fastest, Fast and Simple quality levels in order for Unity to select the Good level in Windows, and now the shadows are back.

 

This works great for my project! thank you very much for sharing.

 

Hi there

@echo4papa 's shader does the job, when the transparent object is a in front of 3D object or Mesh
But if I have a Sprite between that 3D object and my shawdow shaded one, the sprite is no longer visible.

I didn't find an easy and cheap way to get shadows on Sprite, so I'm using a transparent shadow receiver plan in front of my sprite to display the shadow. It works in URP but I have to downgrade to builtin so...

any idea of how to solve that ?

 

Unity's built in renderer does not support shadows on transparent objects. Full stop.

The shaders in this thread hack around that by making an otherwise "opaque" surface render with a transparent blend mode, but it is in fact still an "opaque" object. That means other transparent objects, or the skybox, will not render behind it. You can work around the issue of transparent objects not appearing when behind it by changing the ZWrite to On for the forward pass, but then transparent objects will always render on top.

The solution is to use the URP / HDRP. If you can't, then you don't get shadows on transparent objects outside of very specific hacks like the "transparent" ground the shaders in this thread are attempting.


There is one other work around that works for a single directional light, which is to expose that light's shadow map globally using a command buffer and then using custom code to sample it. But again, this only works for a single directional light. If you want to support shadow casting point or spot lights then you're out of luck.
https://forum.unity.com/threads/usi...ows-in-forwardbase-pass.1080503/#post-6966797

 

same issue,any workround?

 

You can create a new camera to render lower level parts, including the skybox.