Hello,
I tried to create a material based on some vector attributes of a model. Basically it is a very simple tire model which has some velocity vector on all vertices. I want to use this material for scientific
visualizations. The shader nodes setup is shown below
When I render this in Eevee things look like expected. Based on the absolute vector the tire gets colored from blue to red (blue=slow, red=fast). Exactly what I wanted. But using Cycles gives some unexpected results where everything is shown in blue only. I only switched from Eevee to Cycles and left everything else alone.
Any idea what can cause this behavior? Unfortunately I am bound to Cycles because of some geometry nodes requirements.
Thank you in advance for helpful comments!
Hi just tested in Blender 3.4 Alpha (windows x64)
Works as expected.
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Thank you, I will check if it is the Blender version.
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It’s not the Blender version. I get the same result with 3.3 and 3.4 Alpha. But I tried to change the attribute that is used. The one shown above is named “velocity”. That does not work in both versions. But switching to some other attributes works fine in Eevee and Cycles. Following this I used geometry nodes to copy the “velocity” attribute to a new attribute with a different name. In the spreadsheet editor I can see that it has the same values. With this simply renamed attribute the renderings show the same colors between Eevvee and Cycles. So I guess the name “velocity” for an attribute is not a good idea in this case. Maybe since it is already used internally (e.g. for motion blur etc.)?
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Yes, steer away from names like fire, Col, Color, velocity, temperature and Position
I should have asked where this attribute came form, anyways, you found your solution.
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Just in case you run into the same issue: It’s already tracked by Blender team…
https://developer.blender.org/T87494
