So let us assume I have a 3D model of a window and I would like to stretch it like a 9 sliced sprite. How would you go by doing 9 slice on meshes? All I found online was about quads. What about more complicated meshes?
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\$\begingroup\$ What prevents you from writing a vertex shader to scale specific regions of the mesh differently? \$\endgroup\$ – Ocelot Jul 1 '19 at 8:25
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\$\begingroup\$ Cyan used a form of this they called "Stretchables" in building Obduction - you can see them describe it starting around 21 minutes into this GDC Vault video. In their case it looks like an edit-time feature: they bake two sets of UVs in the mesh, one that stretches with the mesh, and one that tiles at a fixed frequency. Then their shader uses the stretched maps to add edge-aware shape detail to the tiling texture of the base map. \$\endgroup\$ – DMGregory♦ Jul 1 '19 at 16:02
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\$\begingroup\$ I've just made a tutorial showing one method of doing this: youtube.com/watch?v=ExNRbEjVT-8 \$\endgroup\$ – Ben Rolfe Sep 28 '19 at 6:03
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As far as I know, this is not as popular as 9-slicing images, so it doesn't come with popular engines.
Having said that, you can always do this manually. Editing a mesh is easier than editing an image, so it's not difficult to separate a mesh into 9 pieces (like you would an image) and either scale the in-between meshes, or tile them, or a combination of both. You don't have to mess with shaders or anything complicated, just the basic transformations of a 3D object are enough.
The process is the same as when using an image, and maybe you can do a "27-slice" if you want the same effect on 3D.
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\$\begingroup\$ How come defining few planes and passing it to the shader is complicated? \$\endgroup\$ – Ocelot Jul 1 '19 at 9:39
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2\$\begingroup\$ @Ocelot some programmers are not familiar enough to be comfortable using shaders. A question of "how to do 9-slice with meshes" hints to me that the OP might not be that experienced, so I provided a beginner-friendly answer. If I was wrong, and OP is experienced with shaders, then other users viewing this question could benefit from it instead. In both cases, OP can solve their problem. \$\endgroup\$ – TomTsagk Jul 1 '19 at 9:43
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\$\begingroup\$ So Tom you are saying, I slice the mesh then scale the mesh in the center? \$\endgroup\$ – Joe Robert Jul 1 '19 at 19:33
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