how to fix pupils (nodes)

Question

ive tried to make a black and white 2d mesh (the 2d mesh does have a curve however) i have used nodes to make a black, shiny mesh texture with glowing white pupils, however for some reason on my eye mesh the white pupils do not show,

on a plane mesh which is a 2d sphere, i get what im looking for when it comes to nodes, however if i try to bend this mesh in any way the pupils shrinks and disappears to the corner and cant be brought back.

this is the same mesh that i have moved with the sculpt tool

this is the mesh that i have made, this is the one that i need help with as the pupils do not show

the material says the pupils are there and yet there not, i know its something to do with the shape of my mesh probably however i need this exact shape for the rest of my character, so if you could help with this it would be most helpful, also this mesh does not have mirror modifier

it does work, it works well honestly, however though you mesh works fine, and mine works with it too

however when i try to move t it shrinks, though i might be because of the orb controlling the pupils needs to stay close to the mesh, my mesh curves a lot

this means the orb shrinks and disappears is there some way to control how far the pupil controller can be from the eye

besides from that the pupil works i just need to know if this new problem is easily solvable

Answer 1

This answer is almost the same as @moonboots..

Your texture is based in Object space, and is a 3D spherical gradient. So the glowing volume (limited by the Color-Ramp) is a sphere around the object origin. What shows on the surface is its intersection with that sphere. As the surface gets further away from the object origin, it intersects with less and less of the sphere, and eventually the glow disappears.

One option would be to put the texture in the space of another object, which you can do in the Texture Coordinate node, in the 'Object' slot.

Here, Empties are used to locate the texture. They are Vertex Parented to the surface, using 3 vertices near the middle. (You could use one vertex, if only the location of the Empty matters to you, and you don't want the orientation to follow the surface) The Empties, (and the sphere of texture around them) will now follow the surface when it is deformed.

This shader tree could be made in many ways depending on the effect you want.. the only important thing for this answer is that the texture is in the Object space of the parented Empty..

The attached .blend is hardly a rig.. but the Left (Camera-Right) Iris-Empty is Transform-Constrained to the Right Iris-Empty, so the right Iris controls both.

Edit: If you want the Empties to cling to the surface under substantiaal distortion, you can add a Shrinkwrap constraint at the bottom of their constraint stacks. How you project, and whether or not you want to keep the transform constraints... I don't know.. that depends on how you want to animate?

Revised .blend:

Answer 2

Actually the problem is that you're deforming the object in 3D. The material setup, that works fine for a 2D object, will deform in 3D. You could fix that with the Mapping node, but as you want to animate the pupil, you need to find another solution, because animating with the Mapping node would be a bit tedious.

A quick way to do it is to create an empty, parent it to the head and give your Texture Coordinate the empty as Object:

Now when you move the empty the pupil follows. You can give it a Limit Location constraint (Local Space mode) so that it sticks around the eye area when you manipulate it:

A more accurate solution would be to give your eye an Image Texture and move the texture with the UV Warp modifier, see video here or Blender Stack Exchange answer here.