Update shader variable

(For demonstration purposes we assume you applied the shader material on a Image component but this works for anything)

For some reason you cannot simply do myImage.material.SetXXX(shaderVarKey, myValue).

To edit a variable you have to

1. have a ref to your Graphic component (for example an Image)

2. implement IMaterialModifier on your mono script

3. implement GetModifiedMaterial

public virtual Material GetModifiedMaterial(Material baseMaterial)
{
	// protected Material _material;
    _material = new Material(baseMaterial);
    _material.SetFloat(progressHandle, currentProgress);
    return _material;
}

4. Each time you edit your script value (which is used in the SetXXX function, here float currentProgress) call SetMaterialDirty on your Graphic component.