Scripted driver expressions not working in material nodes #46753

New Issue

Seth L. · 2015-11-12T22:24:22+01:00

Seth L. commented

2015-11-12 22:24:22 +01:00

System Information
OS X 10.10.1
ATI Radeon HD 4850 512 MB

Blender Version
Broken: 2.76 48f7dd6
Worked: unknown

Short description of error
Scripted driver expressions can be used to animate objects in various ways, but they do not work for material node values.

For example, we can make an object rotate back and forth using the expression: #cos(frame*pi/30)
but we can't use such an expression to make a pulsating glow on a material by using that same expression on an Emission Shader's strength.

To use a simpler example, we can use the single-variable expression #frame to increment some value each frame. It doesn't really matter what the expression is - driver expressions aren't working in material nodes.

They are working in compositing nodes, from what I have observed.

Exact steps for others to reproduce the error

Create an object and a material for it.
In one of the material's nodes (for example an Emission Shader's strength) type in a scripted expression as the value. ("#frame" will do)
Play the animation and see that it doesn't work.

Here is a .blend where the object is animating just fine, but the material is not animating even though the same expression is being used. There is no change in the render, and the node's value does not change as animation is played. The emission strength value remains at -0.5 no matter what expression is inserted. (Before saving the file it showed as the default 1, but after saving and re-loading it shows as -0.5)
driver_expressions_in_material_nodes.blend

**System Information** OS X 10.10.1 ATI Radeon HD 4850 512 MB **Blender Version** Broken: 2.76 48f7dd6 Worked: unknown **Short description of error** Scripted driver expressions can be used to animate objects in various ways, but they do not work for material node values. For example, we can make an object rotate back and forth using the expression: #cos(frame*pi/30) but we can't use such an expression to make a pulsating glow on a material by using that same expression on an Emission Shader's strength. To use a simpler example, we can use the single-variable expression #frame to increment some value each frame. It doesn't really matter what the expression is - driver expressions aren't working in material nodes. They *are* working in *compositing* nodes, from what I have observed. **Exact steps for others to reproduce the error** 1. Create an object and a material for it. 2. In one of the material's nodes (for example an Emission Shader's strength) type in a scripted expression as the value. ("#frame" will do) 3. Play the animation and see that it doesn't work. Here is a .blend where the object is animating just fine, but the material is not animating even though the same expression is being used. There is no change in the render, and the node's value does not change as animation is played. The emission strength value remains at -0.5 no matter what expression is inserted. (Before saving the file it showed as the default 1, but after saving and re-loading it shows as -0.5) [driver_expressions_in_material_nodes.blend](https://archive.blender.org/developer/F254208/driver_expressions_in_material_nodes.blend)

Seth L. commented

2015-11-12 22:24:22 +01:00

Changed status to: 'Open'

Seth L. commented

2015-11-12 22:24:22 +01:00

Added subscriber: @quantumanomaly

Sergey Sharybin commented

2015-11-13 07:25:17 +01:00

Added subscriber: @Sergey

Sergey Sharybin commented

2015-11-13 07:25:17 +01:00

Changed status from 'Open' to: 'Archived'

Sergey Sharybin closed this issue

2015-11-13 07:25:17 +01:00

Sergey Sharybin self-assigned this 2015-11-13 07:25:17 +01:00

Sergey Sharybin commented

2015-11-13 07:25:17 +01:00

This is limitation of old dependency graph. unfortunately, which isn't really easy to solve without doing extra drivers recalculations which will slow things down. This is supported in the new dependency graph so it makes sense to invest time in finishing new depsgraph rather than trying to stretch old one even further.

Thanks for the report, but closing it now.

This is limitation of old dependency graph. unfortunately, which isn't really easy to solve without doing extra drivers recalculations which will slow things down. This is supported in the new dependency graph so it makes sense to invest time in finishing new depsgraph rather than trying to stretch old one even further. Thanks for the report, but closing it now.

Seth L. commented

2015-11-13 16:06:46 +01:00

Got it - thank you for the explanation! Looking forward to when this becomes possible. :-)

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Scripted driver expressions not working in material nodes #46753