Bug HDRP Eye Shader Issue

Okay, here's an example scene that comes with HDRP package samples:


And here's a default cube. As far as I know, it roughly equals 1 meter inside Unity world.
Every eyeball in this scene has 1*1*1 scale. Which means they are deliberately created and imported as gigantic 1-meter eyeballs. And it seems Eye Materials and Eye Shader Graph were calibrated for this scene because they have hardcoded and/or constant values that work only for these enormous eyes. If you import an eye that has a real-world size (or, in fact, any size that is considerably larger/smaller than ~1 meter) you'll get a completely broken material. The same goes for the pivot of the eyeball - It's expected in the same place and with the same rotation as in the example. The pivot part is logical, but it should be documented and mentioned inside the scene, anyway. As for the size, it needs fixing. Not really convenient to import an eyeball with 29x scaling factor and then scale it down to 1/29 to make the shader work. Probably someone has forgotten to change units from feet to centimetres in the DCC package where these eyeballs were modelled.

 

I agree, make the eyeball radius exposed.

 

1306789

 

There is nothing wrong with diffusion and sss.

That wasn't the problem either.

The problem is that you'll have no retina and pupil if your eyeball is not as big as the ones in the example scene. You'll also can get other issues, like tiling, or a pupil that is so large, that it covers the entire eyeball in other cases of size mismatch. That is the problem. It's controlled not by a diffusion profile, but by a constant inside the shadergraph that is set to 0.22 if I remember correctly. If you tune this value, you could scale retina and pupil to match your eyeball mesh, but it doesn't look exactly right, so the problem might be even deeper. And this is a constant value, not a property, anyway. And the necessity of a very specific pivot placement which is not mentioned anywhere is also somewhat confusing.

 

as it was mentioned, there are hardcoded numbers that work correctly only on the huge scale, not sure why, so you can't just use the material to your existing eye at a normal scale, it will not look correctly

I've "fixed" this issue for now by doing:

scaled down the big eyeball to normal human level, noted the scale factor, then calculated the correct "world scale" for the diffusion profiles (both iris and sclera), multiply the existing number of 0.025 to how much you have scaled down the huge eyeball. for normal human was around 0.85

this fixed the reflections, shadows, lighting. looks great.

if you want to use your own eyeball, didn't tried, but I assume you need to import it at the same huge size like that eyeball is, and then scale it down.

now you may find that unfortunately the iris area is too huge for a realistic human. It looks great if you need an anime or pixar type of character but for a realistic look it doesn't look right.

this is simple to fix, duplicate the the SG_Eye shader and rename it to something else to have a backup if you screw something, assign this new shader to your eye material so you actually use it in the scene, then open the shader in the shader editor

here, find all references to "Iris radius", and change the number that is assigned there, in my version the number is 0.22, I've change it to a smaller number, I use something between 0.15 to 0.17, see what works best for you.

make sure you change all the numbers where iris radius is mentioned!!! there are a few. if you don't do it you broke the effect.

also maybe you already know but you need to save the shader to see the changes in the scene,

I've gone a bit further and created a new float variable in the Shader Graph input properties and connected it to every occurrence of the Iris Radius. This way I can change the number in real time in the scene to see how it looks. Probably who prepared the example forgot to do this, probably in future versions this will be already implemented.

Finally you may open the sclera texture in an editing software and play with the luminosity if you think the eye pop up too much comparing with your skin texture.

hope this helps some lost soul, I've lost weeks last year trying to find/create a good eye shader for my model with no luck.

While this unity example shader is somehow broken who create it have all my blessings as I finally have decent human in my game with good looking eyes.

 

I made a copy of the shader and exposed the properties for IrisRadius and IrisPlaneOffset. I used these instead of the hard-coded values in the shader and now the eye material is easier to use. However, something within the shader code still requires the eye mesh to be very large, then scaled down. In this image both meshes are using the edited eye shader. The closest model is from the HDRP samples. This is actually a very large model which is scaled to 0.02437391 in Unity. The other model in the image is a mesh created at actual size, so at scale 1 in Unity. The edited shader allows me to adjust IrisRadius and IrisPlaneOffset, but only the scaled mesh correctly blends the sclera and iris textures. The second eye model seems to lose the sclera texture somewhere in the blending because it doesn't have the same size/scaling ratio as the HDRP sample.



If the HDRP eye shader could be updated so that IrisRadius and IrisPlaneOffset are exposed, and the shader doesn't rely on the mesh size/scaling it would be much appreciated. At the moment the eye shader isn't really useable.

 

Another instance where they didn't check the feature with real projects, just controlled tests.

 

Will there be any more work done on the eye shader? It looks promising, just not quite ready for production use.

 

If I'm understanding this correctly, then we would need different Diffusion profile for each of the size of eye present in a scene right?

Also, what if there's a scene where we need to scale the character(along with the eye) in front of the camera, how should we make the eye behave properly in that instance?

 

The diffusion profile doesn't make any difference.The problem seems to be in the shader and its relation to the eye mesh size. At the moment it isn't useable.

 

Just wanted to say that some months ago I also got this problem with the eyes.

Now I assume most people will use eyes mostly for human size like characters, so why such a stupid arbitrary size of eyes ?

I could even understand if those eyeballs were of 1 unit in diameter (especially if scaling was working), but no someone decided to pull the dimension out of their .... .

 

Isn't there a way that this function could be transferred over to shader side, to calculate the final diffusion texture(I guess this is what gets calculated on the Diffusion profile asset), is this technically impossible?
If it's expensive then you could just add an option to use a baked version or to calculate at runtime using shader (or maybe I'm just an idiot who doesn't understand this topic enough )

 

This will be very helpful. Thank you.

 

Hi, i'm trying to make this shader work on our eye mesh with a 'Skinned Mesh Renderer' to be able to make it rotate with bones. But if the material is set on the 'Skinned Mesh Renderer' the pupil is not visible. If I put a 'Mesh Filter' + 'Mesh Renderer' with the same material, it work.

Maybe someone have a solution for this ?

 

I'm not sure if it's too late, but I also converted this shader from HDRP to URP with acceptable results for the game (in my opinion). I also had trouble applying the shader to a realistic-scale eye and failed after trying all the suggested fixes here.

I figured out that they used the position and the mesh scale to create a Mask that was used to lerp the iris and sclera. You can easily fix this by creating a texture that is similar to that Mask and then replacing it.

 

By the way, we can use another way to avoid creating a texture. This way gives us a better gradient than getting information from pixels. Overall, this shader depends on the mesh's UV, where the center of the iris is at the center of the UV.

forgot to add the function: saturate(distance(UV, float2(.5,.5)) - _Offset)
replace float osRadius = length(positionOS.xy) by this result inside the ScleraLimbalRing and ScleraIrisBlend. Hope this help hehe

 

Sorry for being late here, too. Is the issue that Eye Shader does not work correctly with SMR a Unity Editor bug, or a bug of the digital human package? I'd guess second, shall we still make a regular bug report for this?