I use this in conjunction with Slide Shaders which you can read about here to output the masks as layers within an exr file.

- Introduction.
- Selecting material map slots.
- Assigning the MR labeled Element shader.
- Adding the MR labeled element.
- Conclusion.

Introduction.

The labeled element shader outputs a shader tree to a render element. We’re going to combine three materials together and export them as RGB components of a image. Each channel of this image can then be used as a selection set to edit part of the final rendering in post production.

Selecting material map slots.

First, we need to add the shader to the materials we want to output.  We need to use a material slot that will export the shader but not effect our material. The slot we use is different depending on the materials characteristics.

- if the material is not refractive (ie, doesn’t have any transparency) we can use the transparency colour map slot.
- if the material is refractive, then we can use the anisotropy rotation map slot.
- if the material is refractive and anisotropic then we need to find a new slot to use!

I’m hoping that in the future we might get a ’spare’ slot in the A&D mi material to use for this purpose.

Adding the MR labeled Element shader.

We need to group our materials into threes, one for each channel in the image (RGB).

- In the first material select the slot using the procedure above and add a MR labeled shader.
- Change the shader/ map to store (passthrough) colour to pure red.
- Name the label ‘m1′

- Repeat this for the next material except for the second step change the colour to pure green.
- Repeat this one more time for the third material but change the colour to pure blue.

Now the three MR labeled shaders will have the same label ‘m1′, but they will have different colours. I’ve used the new max 2010 material explorer to help illustrate.

- make sure you have selected your render output file (this will allow max to link the output files of elements to the render output, so if you change the render output file later the elements will also update ).
- open the render dialog and add a MR labeled element on the render element tab.
- change the label of the element to the same as the MR label shader above, in this case, ‘m1′.

Now repeat this but with a new label name ‘m2′ and so on until you have created enough masks for your scene.

When you render images will be created for each MR labeled render element. These images will contain a different mask in each channel (RGB) of the image. These can then be used in photoshop or your favorite post production program for compositing your image.

You’re only limited by your memory as to how many elements you have . Of course, using many render elements can have a detrimental effect on your render times and the use of system memory.

Conclusion.

This is a very handy way of creating masks. It can be a little tricky to set-up (thinking about writing a script here…) but I really like this techniques ability to create masks at render time. By using this with slide shades (follow link at the top) you can save the elements into a 32bit exp file with the final rendering.

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.

I’ve recently updated it to work with class instances, a much more efficient and almost foolproof way of ensuring we get all the maps.

It has two methods of functioning.

1. if the material editor is open, it will open all the maps used in the current material

2.if the editor is closed, then it will load all the maps used in the materials of the selected objects.

This is really handy script if you want to quickly adjust some materials maps in photoshop

for installation, just drop the mzp file onto you max viewport and then add the script to your quad (or menu, or toolbar!).

customize | customize user interface | category : JNScripts

Download the installation file here

Here is a run through of what’s happening under the hood.

--------------------------------------------------------------------------------
--	Open bitmaps in photoshop
--	version 3.1
--	max version 2008, 2009, 2010
--	written by Joshua Newman
--	written		25/05/04
--	updated 	07/04/09
--	www.joshuanewman.net
--	copyright 2004, 2009
--------------------------------------------------------------------------------

-- if the material editor is open, the current materials bitmaps will be opened in photoshop.
-- otherwise all the bitmaps used in the current selection will be opened.

macroScript Photoshop category:"JN Scripts" tooltip:"Load bitmaps in Photoshop." icon:#("JNpshp",1)
(

	On isEnabled return (Try((Selection.count!=0 and selection[1].material!=undefined) or mateditor.isopen())Catch())
	On isVisible return (Try((Selection.count!=0 and selection[1].material!=undefined) or mateditor.isopen())Catch())
	On Execute Do
	(
		bitmaps=#()
		if mateditor.isopen() then
		(
			a=medit.getcurmtl()
			bitmaps=getClassInstances Bitmaptexture target:a
		) else
		(
			sel=selection as array
			for s in sel do
			(
				if s.material!=undefined then
				(
					newbitmaps=getclassinstances Bitmaptexture target:s.material
					for b in newbitmaps do if (finditem bitmaps b==0) then append bitmaps b
				)
			)
		)
		pshop=CreateOLEObject"Photoshop.Application"
		pshop.Visible=true
		for b in bitmaps do pshop.open b.filename
	)
)

Step by step.
macroscript definition.

macroScript Photoshop category:"JN Scripts" tooltip:"Load bitmaps in Photoshop." icon:#("JNpshp",1)
(

This defines the script as a macro, this allows you to add it as a keyboard shortcut, quad menu item, drop down menu item, or button on your tool bar.

	On isEnabled return (Try((Selection.count!=0 and selection[1].material!=undefined) or mateditor.isopen())Catch())
	On isVisible return (Try((Selection.count!=0 and selection[1].material!=undefined) or mateditor.isopen())Catch())

These two lines whether or not the tool is enabled or visible. For example, if it is in a quad menu, then at least one of these conditions must be met for the tool to be visible; 1. Either the material editor has to be open, 2. at least on object must be selected, 3. the first selected object must have a material.

	On Execute Do
	(

Where to start when the script is executed.

		bitmaps=#()

let’s define a variable to hold all the bitmaps we find

		if mateditor.isopen() then
		(

Is the material editor open?

			a=medit.getcurmtl()

if yes then lets get the currently selected material and place it in a temporary variable ‘a’

			newbitmaps=getClassInstances Bitmaptexture target:a

now use the getClassInstances function to get all dependents of the class Bitmaptexture and put them into our bitmaps variable. This will now contain an array.

		) else
		(

ok, so the material editor isn’t open then.

			sel=selection as array

Let’s convert the current selection into an array of objects.

			for s in sel do
			(

Now iterate through that selection object by object,

				if s.material!=undefined then
				(

and check to see if has a material assigned.

					newbitmaps=getclassinstances Bitmaptexture target:s.material

get all the bitmaps used in that material into a temporary variable, returns an array.

					for b in newbitmaps do if (finditem bitmaps b==0) then append bitmaps b

We then iterate through the array and check to see if the bitmap is already listed and add it if it isn’t. I’ve changed this line to remove the appendifunique function since this function was added to Max in version 2008. This will allow my script to work in earlier versions of max.

				)
			)
		)
		pshop=CreateOLEObject"Photoshop.Application"

This creates that OLE communication link with photoshop.

		pshop.Visible=true

This makes photoshop visible on the desktop, if it isn’t already.

		for b in bitmaps do if (doesfileexist b.filename) then pshop.open b.filename else (print b.filename)

Finally, we iterate through our array of bitmaps and check to see that the filenames are valid before opening them one by one in photoshop.

	)
)

Don’t forget to close your parenthesis!

Download simple the mental mill shader here

The lerp (linear interpolation) node handles the mixture of the refraction and the reflection nodes. This mixture is controlled by the falloff node using using the fresnel function.

The comp_set_alpha node controls the transparecy of the shader via the alpha channel. Due to a bug in mental mill this isn’t functioning correctly.

Notice that the falloff amount of the falloff node and the alpha of the composite set alpha node are wired to the outside of the phenomenom and labelled as IOR and opacity. These will appear in the 3ds Max material editor with the amounts that are specified here as default.

Here is a mental ray rendered comparison with the A&D pro glass material in max 2010

As you can see the results are quite different. I was surprised to see that the shelled teapot renders much better with the simple glass mm shader than with the pro material. The solid teapot however is much more realistic using the pro glass.

Interstingly, the reflection on the ground plane has much better detail when using the simple mm glass shader on the teapot. The material of the ground plane is a default pro ceramic. You may notice the reflection of the teapots highlight is very bright in the foreground.

The shadows however suffer from being too dark when using the new shader. Something to work on.

While I was at EUE last week I had the pleasure of talking with Ruediger Raab and Neil Hazard who are partly to blame for this fantastic new viewport rendering in 3ds Max 2010. They both made presentations which included a section on using mental mill shaders with max and they highlighted the some ‘caveats’ and some work arounds that will help you to get your mental mill shaders 3ds Max.

1. contain your material in a phenomenon with a single output for the final node and a single output for the result.

Sounds complicated, but it’s not. When you finish a shader, group it into a phenomenon before saving it for use in max.

If the last node in the phenomenon has more than one output, for example like the illumination_phong then add one more node that has a single output, like a math_colour_add.

Also, make sure that there is only one output on the result of the phenomenom.

This will be fixed in later releases.

2. Express UV coordinates explicitly.

When you use a lookup texture node to load a texture you must assign it UV coordinates. Just wire a state_texture_coordinate node to the texture UV slot on the texture lookup node.

Ruediger suggested that we group this into a phenomenon and save this back the the mm palette for use whenever we need to use it. Good thinking.

3. Scene settings.

Access the scene settings from the render drop down menu;

render | scene settings

From here you can add light nodes from your mental mill palette and one environment shader. I’ve added three point light nodes and changed their intensity and colour.

I’ve then added the lights to the scene by clicking add light button in the scene settings dialog. You can then change the lights position. This is a process only undertaken by the adventurous as you may find it difficult to control. I’ve placed mine in a basic three point layout with a key light and two coloured lights, a warm one at the front right and a cool one lower and from the back. The lights help us see what the shader looks like in mental mill.

Finally I’ve specified the environment shader in the scene setting dialog using the environment shader drop down list. The environment shader will be used in the 3ds Max viewport to create faked reflections. When we render the scene with mental ray the reflections will be ray traced.

Now save this scene and use it as a template when you want to start a new mental mill shader. You can download this mental mill scene set-up from here

4. Mental Ray wont always reload the mental mill material when rendering in max.

There is scurrently a bug in mental ray that causes the renderer to re-use a cached version of the mental mill shader. If you change the mental mill shader in mm and reload it in max then your viewport and material editor should update. The problem is, that when you hit render then mental ray may use the older version it has in memory. You will need to force mental ray to reload the shader by either 1. re-starting max, or 2. saving the mental mill shader with a new name and re-selecting it in the DirectX material in 3ds Max.