MaterialGraph RotateUV appears to scale also

[Amerio.Stephane]

Hello,

I'm trying to rotate a texture in a material graph, and the rotation appears to also scale down the texture:

The mesh is a simple quad with UV from 0,0, to 1,1

As a sample test, here is the graph used:

Am I doing something wrong? Is it the expected behavior for this node? If yes, then how should I compensate the scaling?

Suggestions: add support for a pivot different from (0.5, 0.5)

Suggestions: if the scaling is expected, add support for a compensation in the node as a static switch

Thanks!

[silent]

Hi Stephane,

The Rotate UV node was automatically ported into the graph from the general shader codebase. It works as intended for brushes by rotating the UV coordinates and fitting them into the rectangle, which is why you're observing scale changes.

To avoid this scaling behavior, you can create your own rotation method. Simply create a custom Function node and use the following code:

float2 rotateUV(float2 uv, float angle, float2 pivot)
{
float s = 0.0f;
float c = 0.0f;
sincos(angle * DEG2RAD, s, c);

uv -= pivot;

float2 ret;
ret.x = c * uv.x + s * uv.y;
ret.y = c * uv.y - s * uv.x;
  
// uncomment for fitting in square
// ret *= max(abs(c + s), abs(c - s));
return ret + pivot;
}

Just in case, full matgraph file for that: rotate_uv.mgraph

We plan to add proper Rotate UV methods in future updates (2.21+).

Thanks!

[Amerio.Stephane]

It works! Thanks a lot!

Bonus question: If I want to use the function multiple times in the same graph, I guess I have to put it inside a subgraph and use the subgraph instead, or is there a better way?

[silent]

Quote

Bonus question: If I want to use the function multiple times in the same graph, I guess I have to put it inside a subgraph and use the subgraph instead, or is there a better way?

Yes, that's the right approach for using it across multiple graphs. Just don’t forget to replace it with the proper native version once it’s officially released :)