Hello,

I would like to ask if there is Panda3D (v. 1.10.3) native way to setup GLSL shader subroutine similar to OpenGL example below (I was not successful in finding any useful lead):

Shader:

```
subroutine vec3 shadeModelType(vec4 position, vec3 normal);
subroutine uniform shadeModelType shadeModel;
...
subroutine(shadeModelType)
vec3 phongModel(vec4 position, vec3 norm) {
// The ADS shading calculations
}
subroutine(shadeModelType)
vec3 diffuseOnly(vec4 position, vec3 norm) {
// The diffuse shading calculations
}
```

OpenGL application code:

```
GLuint adsIndex = glGetSubroutineIndex(programHandle, GL_VERTEX_SHADER,"phongModel");
GLuint diffuseIndex = glGetSubroutineIndex(programHandle, GL_VERTEX_SHADER, "diffuseOnly");
glUniformSubroutinesuiv(GL_VERTEX_SHADER, 1, &adsIndex);
glUniformSubroutinesuiv(GL_VERTEX_SHADER, 1, &diffuseIndex);
```

Following link contains more detailed description of the GLSL shader I’m trying to reproduce in Panda3D: