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Last updated - 20/5/2005
Using HDR Images in finalRender
This tutorial describes how to use HDR (High Dynamic Range) images to create lighting using finalRender Stage-1. Before we start here are some useful links that you should have if you're interested in using HDR images;
Possible conflicts
Before starting to work with HDRIs in finalRender you may need to disable a conflicting plugin. If you have MAX 6/7 or have installed the Splutterfish (Brazil) HDR import plugin for MAX 4/5 then you need to disable it as follows; find the file 3dsmax\stdplugs\HDRI.bmi and rename it to HDRI.bmi.old and restart MAX - this will disable it and allow fR's HDR import to work correctly.
Why? Because the built in HDR import filter has problems when used for Distributed Rendering (DR) - it is safer to simply disable it. Be sure to remember to do this on all your render slaves as well!
Important: Installing any of SP1 for MAX 6, SP1 for MAX 7 or MAX 7.5 replaces the built in HDR import filter, you will need to rename or delete the HDRI.bmi file again after you have installed the patch. Again, remember to do this on all your slave machines as well.
RAM
It is important to note that HDRIs are very memory intensive to use - particularly at higher resolutions. You should ensure that you have plenty of RAM in your workstations if you intend to use HDR images.
Now on with the tutorial proper...
Environment slot
The simplest way to use HDR images is to place them in the environment slot as you would any other background image. Choose Rendering -> Environment... from the menu. |
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Click the map slot and choose Bitmap HDR.
Then drag 'n' drop the map slot into the material editor; choose Instance when prompted. You can now edit the properties of your HDR image - the most important of which are the mapping coordinates (see below) and the Exposure settings. Also check that the RGB Channel Output is set to HDR.
Exposure allows you increase/decrease the amount of light the HDR emits, increments of 1.0 are equivalent to 1 f-stop on an SLR camera.
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There are 3 main types of HDR image - Probe (sometimes called Mirrored Ball), Longitude/Latitude and Vertical Cross - each requires different mapping coordinates as follows;
| Image Type |
Mapping Coords |
Probe/Mirrored Ball |
Shrink-wrap
Note: Probe style images usually require rotating by 90 degrees to be used with the shrink-wrap mapping in the environment slot, you can do this from within HDRShop if necessary. |
Longitude/Latitude |
Spherical |
Vertical Cross |
Vertical cross images cannot be mapped directly in MAX, you should convert them to either Probe or Longitude/Latitude using HDRShop. |
Then make sure that fR is using the background for calculating the GI. Oh - and switch the GI on ;) |
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And turn off the default lights or you will get over exposed images. |
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Pros: Easy and simple to setup.
Cons: No fine control over how much light is emitted. Difficult to rotate/position your map correctly. Image must be visible to cast light.
Scene: tut-1-envmap.zip (4 MB) |
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Skylight slot
Instead of using the Environment Slot you can use the Skylight slot available in the fR render parameters. Using the skylight you have more control over how much light is sent by adjusting the skylight multiplier. You may also have a different map visible as your background than is casting your light - useful when you need to use a screen mapped background.
Follow the steps above except place the map in the skylight slot in the render dialogue instead of the environment slot. You must also uncheck 'Consider Background' or you will get overexposed images. You can adjust the skylight multiplier (as well as the HDR exposure) to control the amount of light emitted.
Pros: More control over amount of light. Can use a different map for background.
Cons: Difficult to rotate/position map correctly. Invisible to reflections/refractions.
Scene: tut-1-skymap.zip (4 MB)
Mapped sphere
For the most control it is best to map the HDR image onto the inside of a large flipped sphere that surrounds your scene. Create a sphere that surrounds your scene, next add a Normal modifier and check the Flip Normals option.
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Lastly add a UVW map modifier and choose the correct mapping type (see above).
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From fR-Properties make sure that the sphere is Sending GI, you can turn off send/receive shadows and also receive GI/Caustics as these are not needed.
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Next create an fR-Advanced material and apply the HDRI to the self-illumination slot. Apply this material to your sphere. By using an fR-Advanced material - you can tweak the Send GI multiplier as well as the HDR exposure amount.
Note: Depending on the relative scales of the sphere to your scene you may need to use local GI settings on the sphere to avoid artefacts, do this from the fR-Properties menu if necessary.
Once set-up I usually freeze the sphere and forget about it.
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Pros: Full control of how much light is emitted. Full control over map rotation/placement. Full control over visibility to camera, reflections, refractions, etc.
Cons: Additional geometry to deal with. Possible need to use local GI properties.
Scene: tut-1-sphere.zip (4 MB)
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Using a black & white HDR to control exposure
 The Sachform range of HDR images come with an additional black & white version of the image which you can use to further control the lighting - this can be useful to lower the amount of colour bleed sent from the HDRI.
To use this technique you create a mix map - place the colour image in one slot and the black & white version in the second slot. Then use the mix amount to control the amount of colour. You can use this map combination wherever you would use a single HDR image in any of the above techniques.
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