Handle Uniform Non-Uniform scale in a shader?

I have a shader that's not actually using the vertices for anything (except as a means to define where to draw) but I still want to be able to access the object scale values in an ubiquitous way for uv scaling in the fragment shader.

I can get uniform scale from unity_Scale.w which works fine when my object is uniformly scaled but is there any way to know what the individual xyz component scale of an object/model-transform is if it's been non-uniformly scaled?

That is, without analysing vertex positions.

I thought perhaps unity_Scale.xyz would work, but they always seem to be 0 regardless of unscaled/uniform/nonuniform. Why even use a float4 for unity_Scale if only w is used???.



I also tried using the _World2Object matrix x/y/z component magnitude but they too all seem to be unit length regardless of uniform/non-uniform scale.



I know I could pass in data via the mesh to get this but I need it to be dynamic and don't want to have to attach scripts that update mesh arrays every frame.

 

That is only true if your meshes are batched.

 

Arr I see, did some tests and you're right, _World2Object x/y/z axis vectors do scale, but again only if the object scale is uniform. Got my hopes up for a moment there but I do appreciate the info, probably would have lost most of a day down the road thinking W2O was always unit length so thanks.

I guess there's no simple method to tell what scale an object is inside a shader if it's been non-uniform scaled.

 

I guess the length of the 3D vector (_Object2World[0][0], _Object2World[1][0], _Object2World[2][0]) would give you the scaling of the x axis. Similarly (_Object2World[0][1], _Object2World[1][1], _Object2World[2][1]) for the y axis etc.

Please let me know whether this works.

 

Arr, that explains a lot, thanks.

 

Hmm, my meshes are using a scale of 1, 1, 1 and I'm still having a battle with this matrix MVP. After reading here I changed the way a lot of my meshes for my particle system are created but I'm still having difficulties, which I'm assuming are related to what Jessy is saying about batching.

If anyone cares to take a quick look and offer some advice that would be a real big help.

http://forum.unity3d.com/threads/21...sue-amp-Matrix-MVP-Woes?p=1446312#post1446312

 

Any updates on when this might be changed?

 

bump, is this still true?

 

Hey Aras, thanks for that info. I noticed that the unity_Scale is now auto corrected out, as it is obsolete?

Is there any replacement? (I'm using b17, will be upgrading to b18 soon)

The overarching goal is to get a value that is the difference in position between that portion I am coloring now, and the origin of the model, so that I can apply a gradient effect on them from the top down, which works, but if the origin is at center, it does not.

 

Can you please tell how to calculate scale from _Object2World matrix?

 

vertex and normals come in already scaled, but tangents do not?

 

There is probably a more efficient way to run this operation but this should give you the X,Y,Z scales applied to the object.

Code (csharp):

1. float4 modelX = float4(1.0, 0.0, 0.0, 0.0);
2. float4 modelY = float4(0.0, 1.0, 0.0, 0.0);
3. float4 modelZ = float4(0.0, 0.0, 1.0, 0.0);
4.  
5. float4 modelXInWorld = mul(_Object2World, modelX);
6. float4 modelYInWorld = mul(_Object2World, modelY);
7. float4 modelZInWorld = mul(_Object2World, modelZ);
8.  
9. float scaleX = length(modelXInWorld);
10. float scaleY = length(modelYInWorld);
11. float scaleZ = length(modelZInWorld);

 

this is long long old thread.....i use 4.6.7 f1, v.normal still not correct when non uniform scale...so sad...

 

hi aubergine,u sure v.normal is correct?I use 4.6.7f1,see it not ...

 

any ? I test non_uniform scale in unity5.1.2f1,when scale.y=3 ,batching the mesh,then v.normal look not correct,still not fixed this??

 

it seems both them not work when batching.

 

Hi Aras,how about non uniform scale batching in unity 5，it seem s not work.

 

how about this ?

 

up

 

this is very hard to fixed?I do not think so...Only calculate changed vertex in cpu then upload to vertex buffer for gpu,this is very hard?????Why unity team maybe exist bout 10 years,still not fixed this very very base function ??SO disappoint about unity team

 

This is very annoying...

 

cause you not need to acheive the best performance

 

Can you guys please make UNITY_MATRIX_T_MV scale at the same rate as a normal gameobject, or another keyword that does this. Currently the scaling appears to be squared. This keyword makes it SOOOO easy to make great billboards but the only issue is that it doesnt scale right.

 

hi @Aras or anyone at Unity,

Years and years have gone by,

it is totally undocumented so could you please update on this?

Simple example, here's a shader which has absolutely no textures.

It just draws a brown square:



It simply gets the local position like this

the quad has been scaled,

you can see that if we knew the scaling (or even just the ratio)

it would be very easy to draw "square squares"



How do we get this simple info in the shader ??

 

This was already answered in this thread 3 years ago.
https://forum.unity.com/threads/handle-uniform-non-uniform-scale-in-a-shader.115675/#post-2113659

The only thing that's changed is the name of the local to world matrix, but using the code as is and Unity will fix the name for you from _Object2World to unity_ObjectToWorld.

If your mesh is batched (dynamically or staticly) then the mesh is pre transformed on the CPU and the matrix will have no scale information. You'll need to disable batching either in the project settings or in this shader specifically.

Tags { "DisableBatching"="True" }
https://docs.unity3d.com/Manual/SL-SubShaderTags.html

 

NO,We need Batching to decrease the drawcall at the same time

 

You can have per mesh information about scale, or you can have batching, not both.