just Joshing

I’ve been talking with Robin Deitch from Slide London and experimenting with their mental ray shader called Slide Shaders. Essentially, this great shader will export a multi-layered EXR file from max when you render with mental ray.

‘but I can already save as an EXR file!’ I hear you cry. Why do I need this?

The advantage of this shader is that you can include any number of additional render elements as separate layers in the EXR file. This can then be used in your favorite compositing package such as Nuke, After effects or even photoshop. Of course it is possible to render each element as a separate file but this is much more convenient

You can download the shader from http://slidelondon.com/

You can download my Cornell scene with the Slide Shaders, the rendered exr and a PSD files with adjustments here

Installation.

Extract the correct version into the root directory of Max and re-start.

Required files.

The Slide Shader uses the mr geometry shader object from ctrl.ghost which is maintained by Dave Baker from www.maxplugins.de. This plugin introduces a new geometry object that allows you to place a mr shader in your scene. The file is included in the slide london installation.

Usage.

1. Create a mr Shader object

create panel | geometry | mental ray | mr shader

2. Create a slideElements object

create panel | helpers | mental ray | mr shader

3. Click on the ‘Pick mr Geometry Shader’ button and then select the mr geometry shader created in step 1

4. Enter an output file name

5. Enter an output directory

6. Set the various options, including which standard mr passes you want to include

7. Add all the render elements in the render setup dialog, as you normally would. Give them whatever names you want them to have in the final exr. You can have more than one element of the same type.

8. Click on ‘Build element string…’. This will make a long string of gibberish in the text box below which is what the shader uses to work out what to save, in which format, and what to call it. You need to update this every time you change the render elements in the render dialog.
9. Put the name null.exr in the null file path text box and click ‘Apply to all elements. This assigns the same output file to each render element. This stops max from creating a file for each element, all your elements are going to be exported into the same exr file.
10. Render

Post Production.

You’re now going to have a multi-layered exr file ready for post production and compositing. You can render animations so that rather than having many files for each from, now you only have one.

You can use this in Nuke straight away. Combustion wont accept hdr files, so exr is out.

If you want to open the exr file in Photoshop or After Effects then for a price you can use the excellent fnord ProEXR plugin

Adobe will open exr files just fine, but according to them the ILM specification for exr files doesn’t include layers. Whether or not this is true I don’t know, but what I do know if that I want to be able to use layers. The ProEXR plugin will allow this.