Geometry Nodes Instance Invisible in Cycles #91516

New Issue

Zijun Zhou · 2021-09-19T10:56:01+02:00

Zijun Zhou commented

2021-09-19 10:56:01 +02:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: NVIDIA GeForce MX130/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 471.96

Blender Version
Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-09-18 19:45, hash: bdbc7e12a0
Worked: (newest version of Blender that worked as expected)

Short description of error
No sure whether it is on the Cycles side or Geometry Nodes side. The instances are not visible in the final render, in the viewport you can get it to work by chance if you keep turning the Geometry Nodes modifier on and off. I just happened to get the bug and saved this file, I don't know how to reproduce it from startup.

Exact steps for others to reproduce the error
Based on an attached .blend file

Open the attached file and hit rendered view
Confirm it is invisible, then try to turn the modifier on and off, see it shows up occasionally
Hit final render, see it does not show in the final image

GN Geometry Instance Cycles Invisible Bug.blend
GN Geometry Instance Cycles Invisible Bug.mp4

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: NVIDIA GeForce MX130/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 471.96 **Blender Version** Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-09-18 19:45, hash: `bdbc7e12a0` Worked: (newest version of Blender that worked as expected) **Short description of error** No sure whether it is on the Cycles side or Geometry Nodes side. The instances are not visible in the final render, in the viewport you can get it to work by chance if you keep turning the Geometry Nodes modifier on and off. I just happened to get the bug and saved this file, I don't know how to reproduce it from startup. **Exact steps for others to reproduce the error** Based on an attached .blend file 1. Open the attached file and hit rendered view 2. Confirm it is invisible, then try to turn the modifier on and off, see it shows up occasionally 3. Hit final render, see it does not show in the final image [GN Geometry Instance Cycles Invisible Bug.blend](https://archive.blender.org/developer/F10506925/GN_Geometry_Instance_Cycles_Invisible_Bug.blend) [GN Geometry Instance Cycles Invisible Bug.mp4](https://archive.blender.org/developer/F10488777/GN_Geometry_Instance_Cycles_Invisible_Bug.mp4)

Zijun Zhou commented

2021-09-19 10:56:01 +02:00

Added subscriber: @Eary

Pratik Borhade commented

2021-09-20 07:42:44 +02:00

Added subscriber: @PratikPB2123

Pratik Borhade commented

2021-09-20 07:54:59 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Jacques Lucke commented

2021-09-23 19:47:08 +02:00

Added subscribers: @brecht, @JacquesLucke

Jacques Lucke commented

2021-09-23 19:47:08 +02:00

Don't have a full solution yet, but have some new info. Right now there are two problems:

The Auto Smooth option is set on the object. With this on, an assert is triggered in object_to_mesh.
A second issue introduced in e57ce464c2 hid this assert at first.

This second issue is fixed with the following patch. @brecht, does this look good to you?

diff --git a/intern/cycles/blender/blender_geometry.cpp b/intern/cycles/blender/blender_geometry.cpp
index fca8cb9eda3..63f865c97eb 100644
--- a/intern/cycles/blender/blender_geometry.cpp
+++ b/intern/cycles/blender/blender_geometry.cpp
@@ -80,8 +80,10 @@ Geometry *BlenderSync::sync_geometry(BL::Depsgraph &b_depsgraph,
 {
   /* Test if we can instance or if the object is modified. */
   Geometry::Type geom_type = determine_geom_type(b_ob_info, use_particle_hair);
-  BL::ID b_key_id = (BKE_object_is_modified(b_ob_info.real_object)) ? b_ob_info.real_object :
-                                                                      b_ob_info.object_data;
+  BL::ID b_key_id = (BKE_object_is_modified(b_ob_info.real_object) &&
+                     b_ob_info.is_real_object_data()) ?
+                        b_ob_info.real_object :
+                        b_ob_info.object_data;
   GeometryKey key(b_key_id.ptr.data, geom_type);
 
   /* Find shader indices. */

Still have to investigate how the first issue should be solved.

Don't have a full solution yet, but have some new info. Right now there are two problems: * The `Auto Smooth` option is set on the object. With this on, an assert is triggered in `object_to_mesh`. * A second issue introduced in e57ce464c2 hid this assert at first. This second issue is fixed with the following patch. @brecht, does this look good to you? ``` diff --git a/intern/cycles/blender/blender_geometry.cpp b/intern/cycles/blender/blender_geometry.cpp index fca8cb9eda3..63f865c97eb 100644 --- a/intern/cycles/blender/blender_geometry.cpp +++ b/intern/cycles/blender/blender_geometry.cpp @@ -80,8 +80,10 @@ Geometry *BlenderSync::sync_geometry(BL::Depsgraph &b_depsgraph, { /* Test if we can instance or if the object is modified. */ Geometry::Type geom_type = determine_geom_type(b_ob_info, use_particle_hair); - BL::ID b_key_id = (BKE_object_is_modified(b_ob_info.real_object)) ? b_ob_info.real_object : - b_ob_info.object_data; + BL::ID b_key_id = (BKE_object_is_modified(b_ob_info.real_object) && + b_ob_info.is_real_object_data()) ? + b_ob_info.real_object : + b_ob_info.object_data; GeometryKey key(b_key_id.ptr.data, geom_type); /* Find shader indices. */ ``` Still have to investigate how the first issue should be solved.

Brecht Van Lommel commented

2021-09-27 19:53:32 +02:00

Thanks, I committed that change along with avoiding the problem with auto smooth in this file. But this code is still weak and I think there are more bugs. I need to look into it closer.

Jacques Lucke commented

2021-09-30 12:26:39 +02:00

@brecht Do you have a specific bug in mind that we can put in a bug report? Currently this task is marked as a high priority bug, but it is not really actionable for me.

Brecht Van Lommel commented

2021-09-30 17:47:02 +02:00

@JacquesLucke, I have not had the time yet to investigate this more or confirm there are more issues. But the things I wanted to check:

If geometry nodes generate geometry like metaballs or curves, Cycles has no way of converting those to a mesh. I'm not sure if that can happen right now.
We currently apply autosmooth vertex splitting to the mesh owned by Blender. Not sure if this breaks anything in practice, but it's not great to permanently modify Blender data from the exporter.

I think these are mostly Cycles side things, so will lower the priority and remove the geometry nodes tag.

@JacquesLucke, I have not had the time yet to investigate this more or confirm there are more issues. But the things I wanted to check: * If geometry nodes generate geometry like metaballs or curves, Cycles has no way of converting those to a mesh. I'm not sure if that can happen right now. * We currently apply autosmooth vertex splitting to the mesh owned by Blender. Not sure if this breaks anything in practice, but it's not great to permanently modify Blender data from the exporter. I think these are mostly Cycles side things, so will lower the priority and remove the geometry nodes tag.

Hans Goudey commented

2021-09-30 18:03:16 +02:00

Added subscriber: @HooglyBoogly

Hans Goudey commented

2021-09-30 18:03:16 +02:00

As far as I know, cycles shouldn't have to worry about converting curve objects to meshes anymore, since this is part of curve object evaluation-- if the curve object evaluates to a mesh, cycles will see a mesh object when it iterates through the evaluated objects.

Metaballs haven't been changed though, they will probably still need the displist -> mesh conversion.

As far as I know, cycles shouldn't have to worry about converting curve objects to meshes anymore, since this is part of curve object evaluation-- if the curve object evaluates to a mesh, cycles will see a mesh object when it iterates through the evaluated objects. Metaballs haven't been changed though, they will probably still need the displist -> mesh conversion.

Jacques Lucke commented

2021-09-30 18:03:40 +02:00

Generally, when geometry nodes outputs a curve, it's really just a curve without any thickness. So it can't really be rendered. People use the Curve to Mesh node to give the curve a profile so that it can be rendered. This mesh will then be passed to cycles, not the original curve. Cycles does not have to do the curve-to-mesh conversion.

Brecht Van Lommel commented

2021-11-05 22:06:49 +01:00

Changed status from 'Confirmed' to: 'Resolved'

Brecht Van Lommel closed this issue

2021-11-05 22:06:49 +01:00

Brecht Van Lommel self-assigned this 2021-11-05 22:06:49 +01:00

Brecht Van Lommel commented

2021-11-05 22:06:49 +01:00

After all the latest fixes I think we can close this.

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Geometry Nodes Instance Invisible in Cycles #91516