Mesh batching

roccosaienz · October 18, 2024, 7:30pm

I have two meshes with the same materials and the same vertex and fragment constants. The vertex space is set to World.

Should they be batched in the same drawcall? It seems to me that two drawcalls are used.

Is there something I am missing?

Thanks!

EDIT: The mesh uses triangle strip as primitive type. Is this preventing batching? In any case, triangle strips could be batched using degenerate triangles.
Of course I could batch the strips myself in lua. But just to understand.

Dragosha · October 19, 2024, 4:33am

the same texture?

roccosaienz · October 19, 2024, 8:53am

Yes, same texture

Dragosha · October 19, 2024, 8:58am

Hmm, in that case, try testing draw calls with more of these meshes. Maybe the second DC is a GUI or profiler drawing?

Mathias_Westerdahl · October 19, 2024, 9:00am

When in doubt, check the source code:

github.com

defold/defold/blob/dev/engine/gamesys/src/gamesys/components/comp_mesh.cpp#L320-L352

    
      
          static void ReHash(MeshComponent* component)
          {
              // Hash resource-ptr, material-handle, textures and render constants
              HashState32 state;
              bool reverse = false;
              MeshResource* resource = component->m_Resource;
              dmHashInit32(&state, reverse);
              dmRender::HMaterial material = GetMaterial(component, resource);
              dmHashUpdateBuffer32(&state, &resource->m_PrimitiveType, sizeof(resource->m_PrimitiveType));
              dmHashUpdateBuffer32(&state, &material, sizeof(material));
          
          
    // We have to hash individually since we don't know which textures are set as properties
              for (uint32_t i = 0; i < MAX_TEXTURE_COUNT; ++i)
              {
                  dmGraphics::HTexture texture = GetTexture(component, i);
                  dmHashUpdateBuffer32(&state, &texture, sizeof(texture));
              }
          
          
    BufferResource* br = GetVerticesBuffer(component, resource);
              dmHashUpdateBuffer32(&state, &br->m_NameHash, sizeof(br->m_NameHash));

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Do you have the same buffers? Same vertex declaration?

roccosaienz · October 19, 2024, 11:22am

No, no, each time I add a new mesh I see a new drawcall

roccosaienz · October 19, 2024, 11:26am

The meshes have the same vertex declaration, yes; position, normal and colors.

About buffers. I am not sure I understand what you mean. Each mesh has its own buffer (otherwise they are the same mesh in different positions). But also different mesh could be batched if they have the same vertex data and the same material. Or not?