Displacement node ignores bump node output. #98123

New Issue

tempdevnova · 2022-05-14T18:04:50+02:00

tempdevnova commented

2022-05-14 18:04:50 +02:00

System Information
Operating system: Windows-10-10.0.19043-SP0 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.07

Blender Version
Broken: version: 3.0.0, branch: master, commit date: 2021-12-02 18:35, hash: f1cca30557
Worked: (newest version of Blender that worked as expected)

Short description of error
When connecting a bump node to the normal input of a displacement node the displacement node ignores the bump node and instead defaults to using the geometry node normals.

Exact steps for others to reproduce the error
Test file:

test1.blend

If you connect the color output to the normal input of the displacement node, the displacement node does take the output of the noise texture into consideration.

Thank you and have a nice day!

**System Information** Operating system: Windows-10-10.0.19043-SP0 64 Bits Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.07 **Blender Version** Broken: version: 3.0.0, branch: master, commit date: 2021-12-02 18:35, hash: `f1cca30557` Worked: (newest version of Blender that worked as expected) **Short description of error** When connecting a bump node to the normal input of a displacement node the displacement node ignores the bump node and instead defaults to using the geometry node normals. **Exact steps for others to reproduce the error** Test file: [test1.blend](https://archive.blender.org/developer/F13074429/test1.blend) If you connect the color output to the normal input of the displacement node, the displacement node does take the output of the noise texture into consideration. Thank you and have a nice day!

tempdevnova commented

2022-05-14 18:04:50 +02:00

Added subscriber: @tempdevnova

Philipp Oeser commented

2022-05-17 15:59:23 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2022-05-17 15:59:23 +02:00

Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'

Philipp Oeser commented

2022-05-17 15:59:23 +02:00

I always thought the regular Displacment node can only displace along the surface normals (not along arbitrary directions -- for that I assumed you have to use the Vector Displacement node)
https://docs.blender.org/manual/en/latest/render/shader_nodes/vector/displacement.html
https://docs.blender.org/manual/en/latest/render/shader_nodes/vector/vector_displacement.html

So I am a bit surprised it actually displaces along a modified normal (I thought the normal input was only there to set the normal after displacing...)
Is the documentation wrong then?
Guess this needs some clarification from the #render_cycles team

I always thought the regular `Displacment` node can only displace along the surface normals (not along arbitrary directions -- for that I assumed you have to use the `Vector Displacement` node) https://docs.blender.org/manual/en/latest/render/shader_nodes/vector/displacement.html https://docs.blender.org/manual/en/latest/render/shader_nodes/vector/vector_displacement.html So I am a bit surprised it actually displaces along a modified normal (I thought the normal input was only there to set the normal after displacing...) Is the documentation wrong then? Guess this needs some clarification from the #render_cycles team

Brecht Van Lommel commented

2022-05-17 16:45:21 +02:00

Added subscriber: @brecht

Brecht Van Lommel commented

2022-05-17 16:45:21 +02:00

Changed status from 'Needs Developer To Reproduce' to: 'Archived'

Brecht Van Lommel closed this issue

2022-05-17 16:45:21 +02:00

Brecht Van Lommel commented

2022-05-17 16:45:21 +02:00

There is no bump mapping in the context of displacement, not considered a bug.

tempdevnova commented

2022-05-17 18:54:58 +02:00

To my knowledge the displacement map calculates the displacement as follows: Normal_input*(Height-Displacement)*Scale. I tested this with a node setup in cycles and it indeed gave the same results in all cases except for when the bump node was plugged into the normal input.
There is no bump mapping in the context of displacement There is! By using a height map you can create gradients on the bump map, which then combined with a displacement map gives you the ability to create slopes, which is a very handy trick to e.g. get slopes with greebles on spaceships.

Apart from that is there ana ctual reason why some nodes just arbitrarily behave differently when connected to specific nodes?
To me it seems just as a source of bugs and confusion like e.g. #95671

To my knowledge the displacement map calculates the displacement as follows: Normal_input*(Height-Displacement)*Scale. I tested this with a node setup in cycles and it indeed gave the same results in all cases except for when the bump node was plugged into the normal input. `There is no bump mapping in the context of displacement` There is! By using a height map you can create gradients on the bump map, which then combined with a displacement map gives you the ability to create slopes, which is a very handy trick to e.g. get slopes with greebles on spaceships. Apart from that is there ana ctual reason why some nodes just arbitrarily behave differently when connected to specific nodes? To me it seems just as a source of bugs and confusion like e.g. #95671

tempdevnova commented

2022-05-17 18:56:58 +02:00

So I am a bit surprised it actually displaces along a modified normal (I thought the normal input was only there to set the normal after displacing...) Is the documentation wrong then?
Yes I am certain that it does not do that. You can test it with a weighted normal modifier. The displacement will change as you change the parameters in the weighted normals modifier.

`So I am a bit surprised it actually displaces along a modified normal (I thought the normal input was only there to set the normal after displacing...) Is the documentation wrong then?` Yes I am certain that it does not do that. You can test it with a weighted normal modifier. The displacement will change as you change the parameters in the weighted normals modifier.

Brecht Van Lommel commented

2022-05-17 19:00:35 +02:00

Nodes work different for surface, volume and displacement evaluation. This may be confusing, but it is also useful to be able to share nodes when they are compatible.

Cycles simply does not support bump mapping as part of displacement evaluation, it's only there for surface shading.

Nodes work different for surface, volume and displacement evaluation. This may be confusing, but it is also useful to be able to share nodes when they are compatible. Cycles simply does not support bump mapping as part of displacement evaluation, it's only there for surface shading.

tempdevnova commented

2022-05-17 19:11:15 +02:00

Oh, so I guess it's one of the optimizations, where ceratin nodes are evaluated before others?
But shouldn't it easy to simply include bump mapping as part of the things the displacement modifier evaluates, as it does work with basically all other kinds of inputs or would that drag down performance?

Oh, so I guess it's one of the optimizations, where ceratin nodes are evaluated before others? But shouldn't it easy to simply include bump mapping as part of the things the displacement modifier evaluates, as it does work with basically all other kinds of inputs or would that drag down performance?

Brecht Van Lommel commented

2022-05-17 19:20:43 +02:00

It's possible support, but it's outside the scope of the bug tracker and I consider it low priority.

tempdevnova commented

2022-05-17 20:19:35 +02:00

I mean just remove whatever line of code tells cycles to ignore the bump node and just take the input as is ¯_(ツ)_/¯.

I mean just remove whatever line of code tells cycles to ignore the bump node and just take the input as is ¯\_(ツ)_/¯.

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Displacement node ignores bump node output. #98123