While Indigo is rendering a scene, you can save the HDR buffer into an Indigo Image (file extension .IGI) to resume rendering later.

The Indigo Image stores all the information about a render in progress, so if the same scene is loaded again later (even after the rendering has been stopped and Indigo closed), the current rendering state can be fully restored using the IGI file.

To resume rendering a scene using a saved IGI, follow these steps:

Saving the render progress to an IGI

1. Start rendering the scene.
2. In the menu under "Render" click "Save IGI for resuming"
3. Select the Indigo Image file type in the Save File dialog.
4. Choose a file name for your IGI file, for example "test.igi", and click Save.
5. You can now close Indigo.

Resuming

1. When you wish to resume your render, open Indigo, and select "Resume Render from IGI" from the File menu.
2. You will be prompted to locate the IGI file. Navigate to where you saved the IGI file, and press the "Open" button after selecting it.
3. Indigo will read the location of the original scene file from the IGI. If it is no longer present, you will then be prompted to locate the original scene file, which the saved IGI was made with.

   The IGI doesn't store information about the actual scene to be rendered (i.e. models and textures), only about the state of rendering it, so the scene file is still necessary to carry on rendering. You must open the same scene that you were rendering when you saved the IGI.

4. You can confirm that the render resumed successfully by looking at the status bar – the time elapsed should include all the time spent rendering before the IGI was saved.