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TOPIC: Importons and Irradiance Particles in 3ds Max 2010

Sihina_lahiru

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Posts: 145

Date: Dec 14, 2009

Importons and Irradiance Particles in 3ds Max 2010

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A step by step guide to Using Irradiance Particles and Importons in 3DS Max 2010
with Hyperfocal VHDRIs.

This tutorial requires 3dsmax 2009 or 2010 and the plugin “Ctrl.Ghost” which allows you to control Irradiance Particles and Importons. Irradiance Particles (IP) and Importons are a hidden feature of Mental Ray 3.6. IP and Importons are similar to other GI techniques like Final Gathering.

Using the ctrl.ghost plugin, we can control the look of our lighting and shadows, controlling light bounce, intensity, shadow sharpness and so on. The main benefit of these newMental Ray features is that you can get similar lighting and shading results to Final Gathering/HDRI, but with sharper shadows and less “speckling” or grainy artifacts. In prior versions of 3dsmax out of the box, it has been difficult to get nice looking shadows from HDRI lighting alone, but with IP and Importons, thankfully there is now a great solution to this without having to go and spend up on a copy of VRay.

There are already a few resources out there for IP, however we feel that there is yet to be a complete tutorial on using IP that can be easily followed from start to finish. So here it is!

For this tutorial we will be illuminating an exterior arch viz scene using Hyperfocal Design’s new VHDRI skies. These VHDRIs are named due to their very high resolution, and in most cases the higher dynamic range. You will find that most of Hyperfocal’s normal HDRIs and VHDRIs that are shot during the day will have a brighter sun, and you will be able to achieve sharper, longer shadows. Naturally most of the sunset and overcast images have lower dynamic range and you won’t be able to get sharp shadows unless you place a mr Sky or Physical Sun/Sky or direct light.

So first things first, download Ctrl.ghost from: www.mentalray4design.com (for 09 and 10 versions)

Depending on whether you are using 32 or 64 bit,extract the files into the relevant directories. Make sure you also extract the stdplugin MrGeomShaderObject. Now when you start Max next we are ready to go.

Either load a pre-existing scene or put down some objects to test with. Remove all lights from your scene, turn off Final Gathering and any other lighting you may have.

Go to the create tab -> Mental Ray -> Mr Shader. It is important here that you actually create the Mr Shader gizmo in your scene. It doesn’t matter where, just click and drag out the cubic gizmo anywhere at any size. Now click “Shader” and select Ctrl Ghost.

Next, click and drag the shader from the right hand panel into a free slot in your material editor as an instance. This is where we will be controlling everything to do with the importons and IP. Yes, its odd that its in your material editor but its easy to control and use.

Now load in your HDRI map, we are using Hyperfocal’s VHDRI_Cloudy01_sml.hdr, and were impressed that the full size version (14,000x7,000) actually loaded without crashing/hanging if we need it for larger renders in the future. For lighting purposes there doesn’t seem to be much difference between using the tiny lighting.hdrs or the full size image.

Go to Rendering -> Environment -> Background Environment Map. Choose bitmap, and select your HDR. In the file open window I generally leave gamma set to “use image’s”. Click open, and you are presented with the HDR Load settings. Set your white point so that you have a fairly bright version of the HDR showing in the preview window. You can tweak this later if its too bright or dark. Make sure that under “internal storage” you have “Real Pixels” selected and hit ok.

Now open your material editor, click and drag an instance of the HDRI from the environment map into a free slot, and set it to spherical under mapping coordinates.

All that’s left now is to setup a starting point for IP and Importons. The following settings are certainly far from efficient. If you would like to optimize render times I strongly suggest checking out this post (it provides a visual breakdown of what the settings do):

Mental Images Forum post. http://forum.mentalimages.com/showthread.php?t=4757&highlight=importons

So click on the IP slot in the MatEd (the nice grey box!) and start playing!

The output image has low anti alias sampling (hence the broken lines on the garage door). If you uncheck ‘Rebuild’ after your first render, you can adjust things like AA and AO and the Irradience map will be read from the specified file, in this case the file is named IP_map.

This image uses the following settings:

Ambient Occlusion has been applied to the MR material.

If you’d like a far more technical description of these settings than I could ever provide, check the text file that comes with the ctrl ghost plugin.

If you’d like to boost the dynamic range of any of your HDRIs to create harder edged shadows, you can artificially boost the sun strength in photoshop (CS2 and onwards). Select the sun or an area that the sun could logically appear, and either copy paste in a sun from another, higher dynamic range sky (and hope it matches ok) or you can make a small circle selection and select image exposure, then crank it up a few stops. We found that there seems to be a limit to how far you can take this before you start getting a poor looking “sun”. You’ll have to experiment with each image.

Well that about covers it, so I hope this helps you with your HDRs and exterior lighting with the new IP and Importons! Thanks for reading!

Tutorial by Extra Artists: www.extraartists.com?itp

VHDRI Skies by Hyperfocal Design: www.hyperfocaldesign.com?itp

About Extra Artists - Extra Artists use leading edge technologies to fuse design with 3D graphics to create immersive visual solutions for a range of industries. Our team produce real-time 3D content for games & mobile development, character creations, product renders, architectural visualisations, digital illustrations and 3D logos.

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