Instances becomes transparent in geometry node

[HSDSZ]

Malt version

Development-latest

Blender version

Blender 3.1

OS

Windows 11 64bits

Hardware info

Intel i5-9400F | 8 GB RAM | NVDIA GTX 1660 Ti

Issue description and reproduction steps

In eevee/cycles, the instances auto inherit the shader of original object

If I switch to Malt render engine, the instances become transparent even with set material node added

Can this be fixed from the MALT part?

Attachments

instances become transparent in geo node.zip

[pragma37]

It's weird, because Blender reports the instances as instances of the Sphere object (which they are not) and the Sphere object mesh is empty.
I guess this is a bug on the Blender side? I'd need to take a more in-depth look.

In any case, you can workaround the issue with the Realize Instances node:

[HSDSZ]

Realize instance works, but the number of triangles increases sharply. I found another work around by instance the whole collection instead of the object

[Kolupsy]

@pragma37 are you aware of the changes made to the API regarding geometry instancing in 3.0 + ? I dont quite understand it myself but in case you have not seen it already here is a link to the changes made in that area (scroll a bit down under 'Geometry Instancing') https://wiki.blender.org/wiki/Reference/Release_Notes/3.0/Python_API#Breaking_Changes

[pragma37]

@Kolupsy Seems likely related. Thank you, I'll take a look at it.

Edit: Nope, same issue. :(

[HSDSZ]

With previous Malt version, instancing collection is still a workaround. If I use the latest development version, it does not work

Sample File.zip

[pragma37]

🤦

I reverted the changes I made. Thank you for reporting.

[Kolupsy]

I reverted the changes I made. Thank you for reporting.

Instanced geometry is still not rendered by Malt. What is keeping this issue from being fixed?

[pragma37]

I don't remember the details, but iirc there was no way to retrieve the actual mesh data.

The new API didn't fix that and actually introduced new issues.

[Kolupsy]

The text drawing is not getting positioned correctly for me, though.

Did you ask the Blender Developers about this? I think it would be pretty important to address this issue. I wanted to create a task on the Blender Dev Talk but I actually do not know all the details about this issue. Also I have come across another addon developer working on a custom render engine and they confirmed that they couldnt render instanced geometry in GN using their engine either

[pragma37]

Did you ask the Blender Developers about this?

Not yet. I have to set a minimal reproduction script before that.

[Snowdaw]

In my test case the Circle object has geometry nodes that instances Cube.

In MaltRenderEngine.py around line 202

for instance in depsgraph.object_instances:
            if instance.instance_object:
                obj = instance.instance_object
                parent = instance.parent
                if is_f12 or (visible_display(obj) and visible_display(parent) and
                parent.visible_in_viewport_get(context.space_data)):
                    id = abs(instance.random_id) % (2**16)
                    add_object(instance.instance_object, instance.matrix_world, id)

When rendering Circle, the instance.instance_object is also Circle, when it should be Cube.

To fix this I added the object info node and checked the "As Instance" box which makes it behave correctly again.

Without:

With: