Question Graphics.DrawMeshInstancedIndirect Questions

Hello,

I came across the Graphics.DrawMeshInstancedIndirect feature for a few days.
There are some things I don't really understand yet.

1. Explain the arguments

Code (CSharp):

1. Graphics.DrawMeshInstancedIndirect(instanceMesh, 0, instanceMaterial, new Bounds(Vector3.zero, new Vector3(100.0f, 100.0f, 100.0f)), argsBuffer);

iam only have 1 material for my whole game, so i don't need submeshIndex.

frist when iam generating something outside the bounds, whats then?

argsBuffer is the most confusing thing for me.

Code (CSharp):

1.         // Indirect args
2.         if (instanceMesh != null) {
3.             args[0] = (uint)instanceMesh.GetIndexCount(0);
4.             args[1] = (uint)instanceCount;
5.             args[2] = (uint)instanceMesh.GetIndexStart(0);
6.             args[3] = (uint)instanceMesh.GetBaseVertex(0);
7.         } else {
8.             args[0] = args[1] = args[2] = args[3] = 0;
9.         }
10.         argsBuffer.SetData(args);

that's in the docs, but i don't need submeshIndex so args (0,2,3) are useless for me?

In my case, the shader needs to know the positions and colors of each object.
How can I use the arguments to save space?

this is what iam doing:
(its only do it once in start for testing)

Code (CSharp):

1.         if (positionBuffer != null) {
2.             positionBuffer.Release();
3.         }
4.        
5.         positionBuffer = new ComputeBuffer(instanceCount, 16);
6.         positionBuffer.SetData(positions);          
7.         instanceMaterial.SetBuffer("positionBuffer", positionBuffer);
8.        
9.        
10.         if (colorBuffer != null) {
11.             colorBuffer.Release();
12.         }
13.        
14.         colorBuffer = new ComputeBuffer(instanceCount, 16);
15.         colorBuffer.SetData(colors);
16.         instanceMaterial.SetBuffer("colorBuffer", colorBuffer);

there are 2 buffers (one for positions and one for colors) both are Vector4.
iam also don't know what "positionBuffer.Release()" does.


All i want is:
generate thousants of same meshes, with different colors (also transparency)

currently my gpu (render threat) is 0.2ms but my cpu is over 14.7ms why??

2. is Graphics.DrawProceduralIndirect faster then InstancedIndirect when i try to generate a world?


hope i learn more about it.

Some improvements would be better variables for me to take. The colors do not have to be given to the shader via a Vector4 but as an int (since each color has its own value).

3. what does the 4th Argument in Vector4 positions do?

thank you iam new in scripting shaders so, i only understand single things.

 

Thank you so much for the answers.

What can i do to reduce the amount of data transfered between cpu and gpu, like the ComputeBuffers? iam have two computebuffers, one for position and one for color.

My positions allways integers so is there a way to make it smaller?

Code (CSharp):

1.                 fixed3 localPosition = v.vertex.xyz * data.w;
2.                 fixed3 worldPosition = data.xyz + localPosition;
3.                 fixed3 worldNormal = v.normal;

What is worldNormal I don't know yet, but do all 3 variables have to be set?

 

Hello, sorry but i don't understand what you mean with uint (uint is for me totally new).

My Shader is this:

Code (CSharp):

1. Shader "Instanced/InstancedVertexShader" {
2.     SubShader {
3.         Tags { "RenderType"="Opaque" }
4.         Tags {"Queue"="Transparent" "IgnoreProjector"="True"}
5.         Blend SrcAlpha OneMinusSrcAlpha
6.         LOD 100
7.  
8.         Pass {
9.             CGPROGRAM
10.             #pragma vertex vert
11.             #pragma fragment frag
12.             #pragma multi_compile_instancing
13.             #include "UnityCG.cginc"
14.  
15.             StructuredBuffer<fixed4> positionBuffer;
16.             StructuredBuffer<fixed4> colorBuffer;
17.            
18.             struct v2f
19.             {
20.                 fixed4 vertex : SV_POSITION;
21.                 fixed4 color : COLOR0;
22.             };
23.  
24.             v2f vert(appdata_full v, uint instanceID : SV_InstanceID) {
25.                
26.                 fixed4 data = positionBuffer[instanceID];  
27.                 fixed4 color = colorBuffer[instanceID];
28.                 fixed3 localPosition = v.vertex.xyz * data.w;
29.                 fixed3 worldPosition = data.xyz + localPosition;
30.                 fixed3 worldNormal = v.normal;
31.                                
32.                 v2f o;
33.                 o.vertex = mul(UNITY_MATRIX_VP, fixed4(worldPosition, 1.0f));
34.                 o.color = color;
35.                 return o;
36.             }
37.            
38.             fixed4 frag (v2f i) : SV_Target
39.             {
40.                 return i.color;
41.             }
42.             ENDCG
43.         }
44.     }
45. }

i got two questions:

where to put in uint thing what you say and what does it do.

and does this shader needs #pragma multi_compile_instancing?
because if i remove it or let it in i can't see a different inside unity when i hit play.