Essential tips & tricks for Vray and Mental

Essential tips & tricks for Vray and Mental Ray by Jamie Cardoso

The above image borders were extended by 2000 pixels (in width) to each side using the “Overscan” script.

Extending the camera viewport borders (vertically, horizontally or both) without affecting the camera’s original field of view (FOV)

It’s worth mentioning that some of the subjects discussed here are part of my latest book published with 3D Total Publishing.

There will be times when clients will ask users to revisit old projects, with the purpose to redesign and/or re-render an existing camera view.

When re-rendering an existing camera view, the client may also require users to include more of the 3D scene in the same shot; preferably without affecting the FOV (e.g. almost like extending the borders of a PSD canvas).

In real technical terms such requirements are impossible to achieve, as it defies the physics of any real camera.

Having said that, that’s often what’s required from most users: To do the impossible.    

Until recently, many well-known studios (including myself) would “achieve” the above mentioned request by first decreasing the original FOV of the camera in order to cover new areas of the 3D scene; followed by increasing the original render output size (pixels) many times over in order to compensate for the reduced FOV values. 

The above described process was clearly a “workaround” to meet the client’s request…until I was introduced to an ingenious script called “Overscan”. 

The script was created by Martin (martin@breidt.net) at http://www.breidt.net/scripts/index.html#overscan , to solve the tedious “workaround” described earlier. 


The script only works with standard 3ds Max cameras.

It’s also recommended to save the current 3D scene under a different name prior to using this script, as a precautionary measure.

To implement the script, users are simply required to do the following:

1- Download the script from the above mentioned link.
2-Open the 3Ds Max file, followed by dragging and dropping the script from the folder, directly onto your camera viewport.
3-The script's dialog box should pop up immediately, with the original output image size dimensions. 

The “New Width” and the “New Height” functions allow users to input new dimension values.

The “rel” button locks the original proportion dimensions, so that new added values will always be in proportion to the “Old size” dimensions.

The “Apply Overcan” button updates the camera with the new dimensions entered in the “New Width” and the “New Height” name field. If the “Copy camera” function is enabled, a new camera will be created and named accordingly.

The “Update” button updates the “Old size” dimensions with the new ones entered.

In the figure below, the height of the image output was changed from the original 3000 pixels, to 5000 pixels, without affecting the original camera settings (e.g. FOV, etc).

A new camera was also created automatically, by simply enabling the “Copy camera” function and clicking on the “Apply Overscan” button.

Since the original script was created for standard 3ds Max cameras only; users with a Vray physical camera in the scene, should do the following:

1- First open your VRay Max scene and go to the VRay camera viewport.

2- Press “P” from your keyboard to turn the current Vray camera viewport into a “Perspective” one.

3-Next, press “Ctrl+C” from your keyboard to automatically create a 3ds Max standard camera.

4- A new camera should be created automatically. Next, follow the steps covered earlier to apply the “Overscan” script.

5- Once satisfied with your new camera settings and the output dimensions, run a script to convert the 3ds Max standard camera into a Vray physical camera.

The script I often use is called “MaxCam_To_PhysCam_1.4_proc”. And can be downloaded from the following location:

www.scriptspot.com/3ds-max/scripts/leles-vray-tools

To run the script, simply do the following:

1- After downloading and unzipping the file, simply click on the “MaxScript” main toolbar.

2-On its dropdown list, choose to “Run Script”.

3- The “Choose Editor File” dialog should appear.

4- Locate and open the “MaxCam_To_PhysCam_1.4_proc” from the list.

5- The “Physcam Converter V1.4” dialog should appear. Select the relevant camera(s) from the scene, and click on the “Convert Camera(s)” button.

A new Vray physical camera should be created, named accordingly and selected automatically.

To view the newly created camera, simply press “C” on the keyboard. Alternatively, simply right click on the camera name situated on the top left corner of the camera viewport, and choose the relevant camera.

6- Finally, copy the Vray exposure parameters from the original camera settings onto the newly created one. 
Overriding useless Backburner errors 

Most users would agree that, more often than not, the Backburner can be “spot on” when pinpointing valuable errors in the render(s). However, there are times when it can also be an utter nuisance and ultimately prevent users from meeting their looming deadlines.

Very recently, I was involved in a project that was an absolute joy from the word “go”…until my beloved Backburner began reporting useless errors.

Some of the messages read the following: “3dsmax adapter error: AutodeskMaxDesign 14.12 reported error:JPEG- Memory Error”.

And also: “3dsmax adapter error: AutodeskMaxDesign 14.12 reported error: “…jpeg—Failed to allocate filter tables for this bitmap…”.

The frustration was that, all bitmaps bigger than 1500 pixels were proxied in the scene. Furthermore, the Backburner would render the entire frame with its elements perfectly; followed by re-rendering it over and over again, due to the above mentioned errors.

After few Google searches on the subject, I quickly realized that this was clearly a problem that had many professionals pulling their hair out (if any left) so far.

I nearly threw in the towel on this one... until - Jordan Barlow (Jordan-barlow@hotmail.com)- came up with an ingenious way to override this niggling “bug”.

Please do the following to emulate his approach:

1- Open the “Backburner Manager” dialog first, followed by clicking on the “Edit” toolbar, and choosing the “General settings” option from the dropdown list.

2- The “Backburner Manager General properties” dialog should appear promptly. In the “General” group, enable the “Use Task Error Limit Max Errors Per Task” function, and set it to 1.

This action will limit the amount of times (1) the Backburner will continue to mistakenly try to solve (re-rendering) an error that doesn’t exist, or an error that’s Not affecting any aspect of the render(s).





Create and snap a grid helper perfectly to any given geometry and/or spline, in any angle.


Ever wondered how to create/snap a grid perfectly to any geometry/spline regardless of its position/rotation or angle in a 3D scene?

While this subject was covered to some extent in my latestbook, I have never addressed this specific issue before.

To address the above mentioned issue, users should simply resort to a script called “Create_Grid_At_Object_Pivot”.

The name of its creator is Paul. hormis@hypercent.com (assuming), and can be found in: 

www.hyperent.com/Hyp-Maxscripts.php

Furthermore, to access the above mentioned script one has to download the entire bundle of scripts by clicking on the “Tim-Scripts-Complete-543.exe”.

Once the exe file is downloaded, one should simply click on the exe file to Run-install the entire bundle of scripts.

Through the installation wizard, users can choose the location to create the appropriate folders, the relevant scripts, etc.

The script relevant to this article (e.g. “Create_Grid_At_Object_Pivot” ) will be inside a folder under the name of “Create”. Ensure to have it ticked on.

Alternatively, simply keep all the listed scripts ticked on, and install the entire bundle.


To run the “Create_Grid_At_Object_Pivot” script, simply do the following:

1- Open 3Ds max and create a shape or geometry. Also, rotate/position it in an awkward angle.


2- Next, while the shape/geometry is still selected, click on the “MaxScript” main toolbar and choose to “Run Script” from its drop down list.  


3- The “Choose Editor File” should appear.
Locate (… Tim Scripts; scripts; TiMScripts; Create) and open the script under the name of “Create_Grid_At_Object_Pivot".

 
4- A grid should automatically appear in the correct angle/position, and enabled by default. To test its accuracy, simply begin creating anything in the viewport.  




Using the mental ray connection to access a displacement shader
In the past, a number of people had asked me if there was a way to override the default Arch & design displacement shader with a better one, in order to achieve better results.

While this subject is covered in my latest book, I thought it would be nice to share some of its content here with you.

To access a new displacement shader from the Arch & Design, simply do the following:

1- Open the “mental ray Connection” rollout and scroll down to the “Extended Shaders rollout” group.

2-Unlock the padlock button by clicking on it, and click on its toggle to access the “Material/Map Browser” dialog.

3- I personally choose the “Height Map Displacement” shader from the list, as it’s faster to render. However, feel free to choose another one, if desired.

4- The “Height Map Displacement” shader parameters are simple and self-explanatory.

Vray subpixel mapping function

Again, while this subject was covered in my latest book, I thought it would be nice to share it with those that don’t have the book (yet).

Ever wondered how to correct the artifact depicted in the render below.

The above described artifact can be instantly corrected by simply enabling the “Sub-pixel mapping” function.  

V-Ray:: Irradiance map Interp. Samples
When using the irradiance map, at times the default “Inter. samples” value of 20 may work for a 1920x1080 pixels render. However, when rendering a 5000x2813 pixels image, it may yield artifacts such as the one demonstrated below.




Note: Such artifacts are more noticeable on white or bright surfaces.

To rectify such artifacts, users should simply increase the default “Inter. samples” value to 70 or as high as 90, if necessary. There are extreme cases when one might need to enter higher values.

Note: It is suggested that, by increasing the “Inter. samples” values as mentioned earlier,one may cause the scene to lose depth.

If such happens (debatable), one can still add more depth by using key VRay render elements such as VrayRawTotalLighting; VrayRawLighting; VrayTotalLighting; Vrayshadows; etc).

As mentioned earlier, these subjects have been covered in my latest book.

I hope you have found the tips and tricks useful!