Shader - Avoid vertex Normals influence

Hello everyone,

I am creating a surface shader and I would like to avoid the vertex normal influence and only use the normal maps informations.
Here is an example of the problem.



How can I only use the normal data ? I don't want to handle this in the import settings.
Thanks a lot.

 

Hi Daniel,

Thanks for your answer, I've tried to play with the smoothing angle and sometimes it fixes the issue but I don't want to be dependant of this.
As you said it seems that Object space normal maps can do this.

Is it possible to use Object space normals in a surface shader ?

Edit: Here is an example of Object Space Normal integration

 

This is a problem where you should fix at your modelling application rather than messing with shaders. You should smooth your models normals in your modelling application, and use the highres mesh to bake the normals.

 

The answers here beg the question 'Why would I want to use Tangent-Space normal maps?'
This wiki article over at Polycount might help.

 

This is a very good article thank you RC-1290. Unfortunately I don't want to modify the mesh.

The aim is to avoid vertex normal influence for a tangent space normal map.
But it seems impossible...

 

I never tried, dont even know if it will look good or even will work, but you can also try to average and scale the vertex normals to a minimum before calculating tangent space rotation and only depend on tangents and binormals. Worth a try.

 

It's not possible to do - vertex normals, along with vertex tangents, are required for tangent space maps to work.

In Unity, the normals - along with the tangents - are used to generate the bitangent/binormal. These three are used to create an orthogonal matrix that is used to rotate vectors (usually the light direction and the view direction) from object space into tangent space. These vectors need to be normalized to create a proper rotation matrix, so you can't scale the normals.

These rotated vectors are then dot producted against the values from the tangent space normal map (which is already in tangent space) and lighting is calculated from that.

So when you use tangent space normal maps, you are ignoring the vertex normals - all of the lighting information comes from the tangent space normal map - but you need the vertex normals in order to do anything useful with the tangent space normal map in the first place.



Your issues look like your mesh has rubbish vertex normals. You'll need to properly smooth it in your 3D application and re-export it.

 

Here is an example of what I mean.
This is from the Half-Life Model Viewer with a Dota 2 model. They are using Tangent Space Normals but there's is no influence of the vertex normal.



How is it possible ?

 

They have baked the normal map correctly and it is synced to the Source engine's tangent basis.

 

So, it's seems to be impossible to use those normals with Unity, there will always be some discordance ?

 

They are also avoiding normal map symmetry seams in their shader.
This is another thing that is hard to fix.

 

Thank you all of you for your great explanations. I've made a huge step in Normal comprehension. I was missing the basis concept.