Mesh deformation + normal map rim lighting

Noeski

Hello,

I want to create a spine model that includes a normal map where the normals are setup in such a way to handle rim lighting along the edges (i.e. the normals are angled enough to allow lighting to seep in around the edges). The problem is that if I modify this mesh through animation it will squash and stretch the normal map but I'd like to keep a somewhat uniform lit edge.

I'm curious if anyone has previous experience or there is an existing workflow for handling mesh deformation + normal maps.

Misaki

Noeski In general, you do not need to place normal maps in the Spine Editor. You can create individual images for your attachments and pack them with the same settings by running the texture packer separately. For more information on how to run the texture packer, please see the user guide: http://esotericsoftware.com/spine-texture-packer#Running-the-texture-packer-separately

As an important note, disable Rotation in the texture packer settings when you pack the textures, otherwise the rotated part will be wrong.

There is a thread about the workflow for using normal maps in the past, it may be helpful:
https://esotericsoftware.com/forum/d/14916-normal-maps-creation/3

Noeski

Yes I understand that, but they use the same texture coordinates as the mesh which means when I am animating the mesh the normals will also shift. That makes sense, but if I am trying to mimic 3D then there isn't an easy way to animate the normals in a way that rotates them correctly around the up axis.

Misaki

Noeski I see, let me make sure whether I understand your problem correctly. For example, when you animate a ball with a star symbol, you want to deform the star symbol to show that the ball is rotating in 3D-like movement, but if you deform that part, the normal map will be deformed and the protruding part of the ball will be deformed, making it look wrong. Is this what your problem is? The simple solution I can think of is to animate only that part using a sequence animation (http://esotericsoftware.com/blog/Spine-4-1-released#Frame-by-frame-animation), but I will look for other solutions. Could you please tell us what Spine runtime you are using?

Noeski

@Misaki thank you for the quick reply.

I am using the latest Spine runtime 4.1.

Misaki For example, when you animate a ball with a star symbol, you want to distort the star symbol to show that the ball is rotating in 3D-like movement, but if you deform that part, the normal map will be deformed and the protruding part of the ball will be deformed, making it look wrong. Is this what your problem is?

Yes, exactly!

Misaki

Noeski

I am using the latest Spine runtime 4.1.

Sorry that my question was not clear. I would like to know which runtime you are using: spine-unity, spine-ue4, spine-godot, etc.

Noeski

Oh! I am using Unity.

Harald

@Noeski Unfortunately I can't think of a common simple solution to this problem yet. A partial solution which however requires a custom shader would be to use the derivative functions (ddx and ddy) to determine how much the UV coords change per screen pixel, and then multiply the uv-change by the texture resolution (provided via texturename_TexelSize) to determine how much a single texel has been stretched and then counter-scale (* 1/scale) the normal accordingly.