Friday, 19 May 2017

Maya Tutorial: High Dynamic Range (HDR) Lighting 19/05/2017

Final Result
So HDR stands for High Dynamic Range, and what it is, in a nutshell, is an image or number of images that have been taken so that they may be used to replicate real-world lighting inside of 3D software. So for people who are creating anything with realism factored in, HDR is most likely used in their work.

HDR images are used in '32 Bit' and have the most information, anything lower than 32 Bit is classed as LDR (Low Dynamic Range). Multiple images are taken on a chrome ball, at different exposures, and are combound in order to create a single image, this is what will be used to create the lighting.

When creating a HDR image in Photoshop, there a function already avalible called 'Merge to HDR Pro', which will basically create a HDR image for us, as well as allowing us to tweak certain aspects of our final image.

Once this is made, the final file can be saved out as either an OpenEXR (*.EXR), Radiance (*.HDR;*.RGBE;*.XYZE) or a TIFF (*.TIF;*.TIFF), I have used Radiance.

Unfortunatly the original site for HDR shop no longer allows this application, however, I did mangage to get a hold of HDR Shop so thanks a million for the link to this I greatly appreciate the assitance.

HDR Shop is an old application for unwrapping HDR Images but it was also one of the first, and whilst there is a lot of other applications that can be downloaded that do the same job, and fix a bunch of issues in this program (Distortion and Blurring) its good to know how the technology work and find ways to work around some issue that may be presented.

So the HDR Image needed to be fixed, in order to do this a couple techniques needed to be used, such as cloning and blending. This stage is awfully similar to the first part of the tutorial where we had to alter the chrome ball, taking out any problems and sharpening up areas of our base image.

No Final Gather

Final Gather Turned On

HDR Sphere Visability Turned Off
Okay, so hooking up the image we created up to our scene isn't too bad, it's just like creating a Physical Sun and Sky, but you have to link an image to it. One the HDR image is linked up, the process of the editing your settings, in order to get the lighting to work, begins. The main things that need to be used are Final Gather, Use Background, Image Planes and Materials.

Initial Lighting Test

For this tutorial a backplane image was provided, just to see if the lighting actually worked, which can be seen in the first chrome render. An NURBS surface is used to get an idea of positioning and perspective, but will also be used as a way of creating shading in Maya.

Lighting Refinement

Use Background (Shader) Shadow Effect
Now another minor thing is that when a Use Background (Shader) is applied, it might be an idea to turn off the  Occlusion Mask in the mental Ray settings. This is only a minor thing, but sometimes a black line can stick out in your scene and can kinda kill the immersion in a scene.

Ray Trace Shadows

Chrome Material
This was the final render, the reason the ball is placed so high in the air is to simulate where the chrome ball originally was. Now I could have just left this, but I decided to do a little experimentation, so I brought in Mia Material X, to see what results I could get.

First Glass Test
Raw Image
Colour Managed
It took a little bit of refinement but the glass effect I altered fits pretty nicely with the scene, now that I've got quite a good understanding of how HDR works, hopefully, I will now be able to create even better-looking renders.

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