gradient bump



  • I have plenty of older textures that use gradiant_bump rather than bump. I know that's the old obsolete option and usually, plug the image map into the bump, but how do the strength settings relate? If the gradient_bump is set for .08, should the bump be set to the same or does it need a different number? If it does, is there a conversion formula?

    I'm using superfly right now, but would these answers change for firefly?

    Thanks for any help.


  • Poser Ambassadors

    Hmm. Your question is difficult to comprehend as, basically, you're asking if you can do something dumb.

    Gradient bump maps are more like normal maps than bump maps. You can't just put a gradient bump map into bump because the bump channel interprets height, whereas gradient bump interprets slope or angle.

    The encoding used is one thing - how vendors THOUGHT it works is quite another.

    I'm actually suspecting that the maps you're using are NOT and NEVER were gradient bump maps, but I'd have to see them to be sure.

    In any case, there is no sensible conversion formula. You can't use height where slope is required, and vice versa. To use an analogy, you're asking how to convert a car's location into its speed, and vice versa. They're different concepts.


  • Poser Team

    To make matters worse, I am not even sure what type of Gradient map Poser wants plugged into that channel....



  • So, no. I can't use green beans to make an apple pie. Ok. I will leave it alone or figure out something else stupid to try instead. Thanks



  • Whilst we are talking about maps and their channels, I am a user of Insane Bump in Gimp and I'm still not certain where to plugin the occlusion map that is generated.

    Any takers?

    (BTW - I don't normally use the Diffuse Map as it tends to change the colours of the original image)

    alt text


  • Poser Ambassadors

    @tastiger
    Seems we are in trouble, right?

    FireFly usually has a issue with normal maps. So, Normal maps are out for FireFly.
    SuperFly does not do micro-Displacement. So the Displacement map is out for SuperFly.

    You "could" use the Diffuse in Diffuse, Displacement in Bump, and Specular in Specular.



  • @vilters said in gradient bump:

    You "could" use the Diffuse in Diffuse, Displacement in Bump, and Specular in Specular.

    What I have been doing is using the original texture in diffuse and the displacement in the bump channel and normal in the gradient bump channel, which is where I have seen a lot of normal maps parked. So that just leaves the occlusion map which I have no idea whether it is of any use at all.

    Does the normal map actually make any difference if it is used in the gradient bump channel? Sorry for what may seem like dumb questions but for years I have just gone along with whatever creators have put in the channels and I am now just really starting to explore the material room more fully.


  • Poser Ambassadors

    Occlusion maps represent a general lessening of light due to nearby geometry. You use them when you don't have actual displacement and instead you have to simulation one part blocking light to another part on what is actually a completely flat surface.

    It goes in the Diffuse_Value (which is multiplied with the Diffuse_Color). But if you're using Scatter or some other special node instead of the built-in diffuse, then you should premultiply the color map with the occlusion map. This can be done with HSV (occlusion map into Value). Or it can be done with Color_Math:Multiply.

    In any case, if you're using displacement you have no use for the occlusion map and should not use it.



  • @tastiger said in gradient bump:

    Does the normal map actually make any difference if it is used in the gradient bump channel? Sorry for what may seem like dumb questions but for years I have just gone along with whatever creators have put in the channels and I am now just really starting to explore the material room more fully.

    The Gradient_Bump input is associated with the Gradient_Mode setting below it, which allows you to choose between Gradient Bump (which is the map that used to be used up till Poser 4, with the .BUM extension) and two different kinds of normal maps.

    The problem as I see it is that normal maps you might download as part of a multi-map package rarely say what kind they are, so your only recourse is to try them both and see which one works best - if you can.

    In my opinion, normal maps don't even work very well. I did some tests in this thread at HiveWire: https://community.hivewire3d.com/threads/bump-versa-normal-maps.1448/page-3 which may or may not be helpful.

    @tastiger said in gradient bump:

    I'm still not certain where to plugin the occlusion map that is generated.

    When I get one of those, I plug them into the Diffuse_Value input, and also Specular_Value, the same as you would with an Ambient_Occlusion node. The advantage of having a map is that AO has been pre-calculated for you so the renderer is spared the heavy lifting.



  • I also have a bunch of older materials that load bump maps into the Gradient Bump channel, and if an item has more than one or two material zones, I use the "fix bump maps" command in D3D's XS Shader Manager to move all the bump maps to the Bump channel instead. I'm not sure how the script figures out the bump strength, but it always just seems to work.

    I'm a little surprised by the responses you got, as apparently other users have not run into the issue of materials that have grayscale bump maps attached to the Gradient Bump channel instead of Bump. But the fact that XS Shader Manager has an option to fix the problem suggests that you and I are not the only ones who've encountered it!


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