3 meshes, 1 material, 3 Draw Calls - Why?

Unity Engine
1

Hi Folks.

I expected to get 1 draw call, not 3.

I have a vehicle about 1000 polys, so no dynamic batching. The vehicle is setup with the three meshes:

Vehicle
+Body
+Decal1
+Decal2

The texture atlas is as such

1 2 3 4
5 6 7 8
9 A B C
D E F X

where 1-F = paint jobs and X is a set of numbers in a 512x512 cell at the bottom right of the atlas:

0123456789
0123456789
0123456789
…etc.

where 0-9 is the actual digits that go on the decals. The uvs get shifted up/down and left/right to match the digit/font for the car.

To change the paint job on the car, I shift the UVs on the body mesh. To change the numbers (Decal1 and 2), I shift the UVs of the Decal1 and Decal2 meshes.

It all works. Except it’s three draw calls, not 1.

If I combine the meshes, it goes to 1 draw call, but the numbers are set to 00, and thus my UV-moving script doesn’t work properly.

I gather I can’t move the UVs because of the mesh combining, maybe I need to “reread them” after the mesh has been combined.

Is there a best practice for this? Am I missing something obvious? How do others manipulate UVs after mesh combining?

2

3 draw calls are becaue of the shaders / lights / shadows.

Anyway ppl need to stop worrying about draw calls :stuck_out_tongue:

3

You worry about them when you’re fitting it into an iOS device :slight_smile:

Anyway, just merging the meshes gives me 1 draw call. I need to be able to manipulate the uvs of 3 different sets of polygons inside the same model using the same atlas, just different parts.

I don’t know how to access the uvs after the mesh combine.

4

Sounds to me like you already answered your own question.

–Eric

5

That doesn’t answer why the two decals weren’t batched, then. They are <50 polys each. Then it should be 2 draw calls with tem dynamically batching.

It also doesn’t answer the sub-question (new post?) - how do you access/manipulate different uvs for different polygons inside a mesh?

Or am I on Mars?