Init:

renderTarget1 = new RenderTarget(...);
renderTarget2 = new RenderTarget(...);

worldScene = new Scene();
uiScene = new Scene();

for(var i=0; i<100; i++)
{
  human = CreateHumanEntity();
  worldScene.Add(human, ...);
}

renderTexture = new RenderTexture(...);

renderTarget2.SetTexture(renderTexture);

quad = CreateSimpleQuadEntityWithTexture(renderTexture);
uiScene.Add(quad, ...);

worldCamera = new Camera(...);
minimapCamera = new Camera(...);
uiCamera = new Camera(...);

uiCamera.SetTransform(...);

Render loop:

renderTarget1.Clear();
renderTarget2.Clear();

worldCamera.SetTransform(...);
minimapCamera.SetTransform(...);

worldCamera.Render(worldScene, renderTarget1);
minimapCamera.Render(worldScene, renderTarget2);
uiCamera.Render(uiScene, renderTarget1);

class Camera
{
    float position[3];
    float lookAt[3];
    float upVector[3];

    float fieldOfView;
    float aspectRatio;
    float nearPlane;
    float farPlane;
}

class EntityRenderGroup
{
  // Mesh, l2w matrix, material information (scalars, textures), etc.
}

Camera::Render(scene, renderTarget)
{
  SetupRenderParams(scene.RenderParams, renderTarget);

  var renderGroups = scene.CullAndMakeRenderGroupsByEntities(this.ViewFrustrum);

  Sort(renderGroups);

  for (var i = 0; i < renderGroups.Count; i++)
  {
    var renderGroup= renderGroups[i];

    renderGroup.Render();
  }

  // glPop...
  CleanUp();
}

RenderGroup::Render()
{
  // Assign matrices, buffers, textures
  // glPush...
  SetupArguments();

  glDrawArrays(GL_TRIANGLES, 0, vertexCount);

  // glPop...
  CleanUp();
}