U 3.0 surface shader : access to list of other objects

Unity Engine
1

Can surface shader access a list of other objects’s position?

I’d like to darken objects based on other object’s proximity to simulate inter-object AO.

2

“Surface shaders” is not some magic that suddenly gives you access to everything in the world :slight_smile: Surface shader is just something from which a vertex a pixel shader is generated.

A vertex shader works on one vertex.
A pixel shader works on one pixel.

They don’t know anything about any other vertices or any other pixels or any other objects.

3

That said, you can make a shader with a set of vector properies and set them to the positions of nearby objects in Update(). This is nothing new in Unity 3.

4

Thanks guys, this is so frikin’ awesome !!!

Now I’d like to compute the delta position on the shader, so all the c# script does is pipe in the occluding object’s positions.

I see that surface shaders have IN.worldPos and I tried the same keyword for s.worldPos, Unity is giving me an error. Is the keyword different ?

error : “Program ‘surf’, expression left of .“worldPos” is not a struct or array at line 29”

5

What is “s.worldPos”? Moar context please.

6

half4 CustomProxymityLighting (SurfaceOutput s, half3 lightDir, half atten)

s.worldPos is the world position of the surface point that’s being processed

7

Well, SurfaceOutput structure does not have a member “worldPos”. SurfaceOutput is declared in UnityCG.cginc, and it is:

struct SurfaceOutput {
    half3 Albedo;
    half3 Normal;
    half3 Emission;
    half Specular;
    half Gloss;
    half Alpha;
};
8

Is there further documentation on what I can put after #pragma ? ie. #pragma surface surf Blinn or Phong? (They don’t work at the moment, only Lambert).

9

It’s BlinnPhong, all one word. All the options are documented on the first page about surface shaders.