negative scale make wrong v.normal?

[dreamerflyer]

I use v.noraml to moving the vertex position,but when negative scale ,the moving is wrong,how to fixed this?

[dreamerflyer]

it seems make the v.normal normalized when scale.x=-1,why?

[mholub]

Show us the code.

Generally you can’t use model matrix to transform direction vectors when scale is nonuniform (as in your case, x = -1, y = z = 1), only position ones.

For completely generic matrix you should use inverse transpose matrix (see Unity - Scripting API: Matrix4x4.transpose and Unity - Scripting API: Matrix4x4.inverse methods) to get corresponding transformation matrix for direction vectors.

In your case I think there should be more simpler solution, but I am too lazy now to get the paper and calculate it.

Transforming Normals [RMS] - explanation of why you can’t transform normals with non-uniform scale matrix

[dreamerflyer]

@mholub

Show us the code.

Generally you can’t use model matrix to transform direction vectors when scale is nonuniform (as in your case, x = -1, y = z = 1), only position ones.

For completely generic matrix you should use inverse transpose matrix (see http://docs.unity3d.com/ScriptReference/Matrix4x4-transpose.html and http://docs.unity3d.com/ScriptReference/Matrix4x4-inverse.html methods) to get corresponding transformation matrix for direction vectors.

In your case I think there should be more simpler solution, but I am too lazy now to get the paper and calculate it.

http://www.unknownroad.com/rtfm/graphics/rt_normals.html - explanation of why you can’t transform normals with non-uniform scale matrix

Thanks your reply !my code is very simple.give difference vector for vetex normal .like this:mesh.normal=dirs;then in shader:float3 pos =v.vertex;pos=pos+time.y*v.normal;I don’t use the matrix to scale,it is unity do it.

[dreamerflyer]

Help

[dreamerflyer]

i want to use unity_scale for control nonuniform scale and v.normal by this:

v.normal=v.normal*unity_scale.w;it dosen’t work…

[dreamerflyer]

@mholub

Show us the code.

Generally you can’t use model matrix to transform direction vectors when scale is nonuniform (as in your case, x = -1, y = z = 1), only position ones.

For completely generic matrix you should use inverse transpose matrix (see http://docs.unity3d.com/ScriptReference/Matrix4x4-transpose.html and http://docs.unity3d.com/ScriptReference/Matrix4x4-inverse.html methods) to get corresponding transformation matrix for direction vectors.

In your case I think there should be more simpler solution, but I am too lazy now to get the paper and calculate it.

http://www.unknownroad.com/rtfm/graphics/rt_normals.html - explanation of why you can’t transform normals with non-uniform scale matrix

c# 
Start():
Matrix4x4 invertTraM=new Matrix4x4();
                invertTraM.SetTRS(Vector3.zero, Quaternion.identity, gameObject.transform.lossyScale);
                invertTraM=invertTraM.transpose;
                invertTraM=invertTraM.inverse;
                renderer.material.SetMatrix("_inverTraM",invertTraM);
 
shader:
  half3 vNormal=mul((float3x3)_inverTraM,v.normal);

hi mholub,I try use the matrix to fixed that,but my code not work,need your help,thanks advance!

[dreamerflyer]

and i found this very very old thread about same problem…NO WAY to fixed this??..

Handle Uniform Non-Uniform scale in a shader?

[dreamerflyer]

Graphics: Unity 4.0 adds a “Read/Write Enabled” option in Mesh import settings. When this option is turned off, it saves memory since Unity can unload a copy of mesh data in the game. However, if you are scaling or instantiating meshes at runtime with a non-uniform scale, you may have to enable “Read/Write Enabled” in their import settings. The reason is that non-uniform scaling requires the mesh data to be kept in memory. Normally we detect this at build time, but when meshes are scaled or instantiated at runtime you need to set this manually. Otherwise they might not be rendered in game builds correctly.

maybe this work?But new mesh in runtime how to enable this?

[dreamerflyer]

Any help?

[kilik128]

so after all any idea ?

[rohitvishwakarma1819]

@dreamerflyer

I use v.noraml to moving the vertex position,but when negative scale ,the moving is wrong,how to fixed this?

Hey @dreamerflyer did you find any solution ??
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