Bump modes not the same between CPU and GPU

[andybot_cg]

I tested out the various common bump methods that work (and sometimes don't) between CPU and GPU, and I'm finding a lot of mismatches. Would it be possible to get the two engines working more similarly for something as basic as bump mapping. In the meantime, I am curious is there is a "switch" node that would allow a material to go to one set of nodes for CPU and another set of nodes for GPU? Blender file attached. Also note that fog color doesn't render the same.

[andybot_cg]

normal maps seem to match, though again you can see the refraction fog color is different. (There also seems to be a difference in the IOR that is calculated between CPU and GPU)

Here is also the triangulation bug with the normal "Bump" setting instead of "From Bump" Seems the problem is only in CPU rendering, GPU renders regular bump fine.

[andybot_cg]

So I got a little mixed up with versioning and uploaded some incorrect info. Here is a simplified blend file with two materials for comparison. The difference is one has the bump method as "Bump" and the other has "From Bump" They are rendered once each with CPU and GPU.

I also dropped in the first version of "Water_Seas-GPU-bump" material from the post above - the one that rendered with no bump effect in the 2nd image "gpu_compare-GPU-tex2.jpg". Seems the issue is that if the multiplier is not 100%, then "From Bump" will not render in either CPU or GPU. In this case, a multiplier of 40% produces no bump effect.

Thanks,

Andy

[poseidon4o]

For the "Water_Seas_bump" material remove "Bump Shadows". Also your noise texture seems outdated, re-create with newer version to get the proper sockets and also connect the color output to the "Normal Texture" socket:



With these changes all 3 materials render bump both on CPU and GPU.

[andybot_cg]

Thanks for sorting that out! It seems the refraction fog color still does not render the same though. Is that a separate issue?

[andybot_cg]

Now that I have the bump mapping settings in order, I see the refraction color is still not the same. What is causing the GPU refraction to be lighter in color than CPU?

[savage309]

Now that I have the bump mapping settings in order, I see the refraction color is still not the same. What is causing the GPU refraction to be lighter in color than CPU?

Fog works somewhat differently on the GPU.
Keep in mind that GPU and CPU are different render engines, and they will never render 1:1 (nor this is our goal). If you want to switch mid project from CPU to GPU it will not work great for you. Check this to see if it can be of any help for intro to GPU http://dabarti.com/vfx/short-guide-t...with-v-ray-rt/

Best,
Blago.

[andybot_cg]

OK, as long as this is not some bug, I can deal with the difference. At this point, I am not going to GPU for production, as there are still some gaps in supported nodes. I do find it useful as a fast way to preview a scene, and of course looking forward to such a day as when RT feedback comes to Blender. In general though, I want to make sure my materials library is compatible with GPU.

[savage309]

We have a note to check if it is a bug though. I just wanted to clarify that although the engines share the same ui and almost the same features, they are different and sometimes differences can be normal.
Best,
Blago.

[andybot_cg]

We have a note to check if it is a bug though. I just wanted to clarify that although the engines share the same ui and almost the same features, they are different and sometimes differences can be normal.
Best,
Blago.

Thanks for checking. Yes, I'm quite aware they are different engines. There are a few other subtle differences, like bump map effect doesn't produce exactly the same result. (You can see in the water example above that the refraction through the mesh doesn't show the background exactly the same, I've noticed this in other examples as well) The fog color is quite noticeable though, so it would be nice to get these closer. Here's another example file. I took out bump mapping and it's all geometry, just to make sure the bump mapping wasn't producing any unwanted effects.

Oh yeah, one other minor thing: Is there a way to increase the resolution or AA of the procedural checker pattern in the dome light when using GPU? I couldn't find how to increase the resolution of the pattern.