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I just want to know how to bake my normal maps using the Cycles render engine. When I use a cage in Cycles, should I target the cage between high poly and low poly objects? Or should I create another mesh with similar proportions to the related mesh to bake, as an intermediate object to use as a cage? Does there exist any boundary box to catch the rays and make a good normals with constant colors, rather than odd or very dark.

I have used Xnormal in some cases, but I would prefer to learn to use cycles, and to target OpenGL for my normals. I have been using Blender since 2013, so I know a little of everything.

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Cage baking should follow more of less the same principles in any baking system. It is only really necessary to have a custom cage when trying to capture hard edges, smooth organic models shouldn't need one, as the ray distance parameter will effectively create on for you. The purpose of a custom cage is to modify the direction that the rays are cast when determining where to draw the normal info from, which is particularly important form split normals, as otherwise you may miss some directions in the bake (see here).

The best starting point for creating a cage is to just inflate the low poly (this effectively is what the ray distance parameter is doing internally). From there you need to look at you high poly and low poly together and look for problematic hard edges and tweak the cage around these errors. Until you get more experienced, some trial and error will be required. Be aware that Cycles requires that the cage has the same topology as the low poly.

The blender manual covers cages briefly at the bottom of this page.

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  • $\begingroup$ So , I need to "inflate" the Lowpoly one? you mean "schriwnwrap" modifier? (how can range to Inflate with this modifier?) ...it is just hard edges make difficult to catch lights? the cage in cycles must be the same polycount as the lowpoly....so that cage will be a duplicate with modifiers to get the shape..? $\endgroup$
    – RG1988
    Commented May 5, 2017 at 2:58
  • $\begingroup$ @ReifusRufus inflate can be done in a couple of ways, using alt-s to scale up in edit mode or a displace modifier with no texture (this will just use the fixed displace amount, which you can tweak). The purpose of a cage is to modify the direction that the rays are traced, which is derived from normals. Yes, the cage should be the same polycount as it must have the same face topology. $\endgroup$
    – Sazerac
    Commented May 5, 2017 at 3:03
  • $\begingroup$ for organic shapes , as human body is not useful right? if I want to make normals for a biselected building with "weith bebels" or "mean creases" to sharp the edge is the most useful case? $\endgroup$
    – RG1988
    Commented May 5, 2017 at 4:16
  • $\begingroup$ If you are using stuff like edge splits or split normals it is important. If your low poly still has bevels instead, it may not be so important. For human characters, yeah, it not likely to be so useful. The polycount page I linked has lots of tips for getting good results from normal bakes, it does mention max a lot, but for the most part is appropriate for any software. $\endgroup$
    – Sazerac
    Commented May 5, 2017 at 4:56
  • $\begingroup$ ok , one last question , when I use "mark sharp" (edit mode-> control+e -> mark sharp ) and my model has some "mean creases" or "weith bebel" , should I take it as a "must" ? or not to bake ? thx for the time and the link is useful . $\endgroup$
    – RG1988
    Commented May 5, 2017 at 13:47
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Usually for simple objects, I take the bake target, duplicate it and add a Solidify modifier, uncheck the fill case, apply it and remove the internal part of the mesh by selecting a vertex and Ctrl+L to select the connected mesh. Works most of the time, but for more complex object it ended giving me an error message:

"Invalid cage object, the cage mesh must have the same number of faces as the active object"

And that even if the number of faces is the same.

So I had to find another trick that achieved a better result:

Add a Displace modifier, tweak the strength up from 1 to 1.2 ... and voila!! You can either apply it or activate on cage on the modifier. the second option allows you to tweak it later if the bake isn't perfect.

Hope this helps.

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