Multipe Instances from a Shader

Unity Engine
1

Hello folks,
I am trying to create a shader that will help me create an animated 3D stadium crowd. I currently have a rigged and animated mesh that I want to use. I was hoping to use a shader that will create multiple instances of this mesh with the verts offset by different amounts.

Shader "OffsetCrowd"
{
	Properties
	{
		_Color("Main Color", Color) = (0.5,0.5,0.5,1)
		_MainTex ("Texture", 2D) = "white" {}
		_Offset("Vertex Offset Translation", Vector) = (0,0,0,0)
	}
    SubShader
    {
		Tags {"RenderType" = "Opaque" "IgnoreProjector"="True"}
	    CGPROGRAM
	    #pragma surface surf Lambert vertex:vert
		struct Input
		{
			float2 uv_MainTex;
		};
		float4 _Offset;
		void vert (inout appdata_full v)
		{
			v.vertex.xyz += _Offset.xyz;
		}
		sampler2D _MainTex;
		float4 _Color;
		void surf (Input IN, inout SurfaceOutput o)
		{
			o.Albedo = tex2D(_MainTex,IN.uv_MainTex).rgb * float3(2,2,2) *_Color.rgb;
		}
		ENDCG
    } 
    Fallback "Diffuse"
}

So with this shader I can offset the mesh by a set amount along the objects axis. And if I make a few copies of this material, each with different _Offset values, and put them on the mesh’s Skinned Renderer, I get the effect I want. The problem with this is the excessive number of draw calls. Is it even possible to generate multiple instances of a mesh through a shader?

Any ideas or suggestions for creating an efficient 3D animated crowd are welcome.
Thanks in advance,
Andrew

2

The more materials you have, the more draw calls you will get. In order to reduce draw calls, you should try and reduce the number of materials you use, and enable batching. This will allow Unity to combine meshes which share the same material, and render them in the same draw call.

There is something called GPU mesh instancing, but Unity does not support it.

3

Thanks for the speedy reply Daniel. I am aware that additional materials on dynamic mesh will increase the number of draw calls. I was hoping that with the right shader a single material could do the work. I don’t know anything about GPU Instancing but if this is what it is, it sounds like exactly what I want.
Any other suggestions are welcome.

4

Unfortunately, the best you can do with Unity is to batch your meshes, either manually or by using static or dynamic batching.