Debugging batch groups

LeXXik · January 19, 2023, 4:42pm

I am adding 2 mesh instances that were generated using mesh API into a single batch group (2 render components, 1 mesh instance each, same batch group). However, they still draw in separate draw calls. What would be an approach to understand what is causing them not being drawn in a single call? Does batch manager have some additional logs that would indicate the reasons?

mvaligursky · January 19, 2023, 5:41pm

None at the moment. Are your mesh instances using the same material? Any different uniforms set up on the mesh instances?

Leonidas · January 19, 2023, 8:29pm

Is there a case their bounding box is larger than the max aabb size?

You can check here all the grouping rules applied:

github.com

playcanvas/engine/blob/96141aad3a19b4d3744a14c4f5198f4416a018d2/src/scene/batching/batch-manager.js#L466

      
        
                        }
                    }
                }
            }
            
            

            
/**
             * Takes a list of mesh instances to be batched and sorts them into lists one for each draw
             * call. The input list will be split, if:
             *
             * - Mesh instances use different materials.
             * - Mesh instances have different parameters (e.g. lightmaps or static lights).
             * - Mesh instances have different shader defines (shadow receiving, being aligned to screen
             * space, etc).
             * - Too many vertices for a single batch (65535 is maximum).
             * - Too many instances for a single batch (hardware-dependent, expect 128 on low-end and 1024
             * on high-end).
             * - Bounding box of a batch is larger than maxAabbSize in any dimension.
             *
             * @param {MeshInstance[]} meshInstances - Input list of mesh instances
             * @param {boolean} dynamic - Are we preparing for a dynamic batch? Instance count will matter

LeXXik · January 20, 2023, 6:44pm

Made a little repro project. Except it doesn’t repro In the sample project it batches correctly:

https://playcanvas.com/editor/scene/1643083

The setup is same, so not sure what’s up. Going to debug more. Also, in the sample project the mesh has issue with shading (default standard material). Any idea what I missed? I don’t have that issue in the real project.

yaustar · January 23, 2023, 10:03am

Shading looks fine?

LeXXik · January 23, 2023, 10:20am

The light falls directly onto them? You can see the shadows direction. I would expect them to be the same whitish color as the bottom plane. The material is a default standard material. Here, I put a box behind for reference:

Leonidas · January 23, 2023, 10:25am

@LeXXik are you generating normals too?

LeXXik · January 23, 2023, 10:27am

@Leonidas I don’t! Ok, that would be it then.
facepalm

Will continue debugging the original project for batching issue and will update this thread, if there is any finding.

Leonidas · January 23, 2023, 10:29am

Yes, seems to work then:

const indices = [0, 1, 2];
mesh.setPositions(positions);
mesh.setIndices(indices);
mesh.setNormals(pc.calculateNormals(positions, indices));
mesh.update();

LeXXik · May 2, 2023, 5:27pm

Still struggling with the batcher. At least, I’ve narrowed it down to an issue related to timing. Here, I made a small repro:
https://playcanvas.com/editor/project/1070373

Both triangle and box belong to the same batch group. There is a function init() that generates a triangle. If I call it immediately, then I can see both triangle and box. If I call it on delay, then triangle never appears. Any ideas?

VS

Leonidas · May 2, 2023, 5:53pm

This seems like a bug to report, most likely a grouping issue with the batcher. If I call batcher.generate() in the console manually, I get a second duplicate box batch.

LeXXik · May 2, 2023, 6:23pm

Made one for tracking: