Discussion on HDRI, Lightprobes, Reference images, and the like.
So, how do you get the great natural lighting and reflections you see in the movies when combining 3d with live action? You use HDRIs, Lightprobes, and Reference Images.
First, HDRI
HDRI stands for high dynamic range image - sometimes referred to as a radiance map. The dynamic range of a scene is the contrast ratio between its brightest and darkest parts. A HDR image therefore has a greater dynamic range than a standard image file such as a jpeg, tiff etc., which is a low dynamic range image. HDR images have the important property that their pixel values are proportional to the amount of light in the original environment where the HDRI was captured. So the benefit of the HDR format is that it stores the amount of luminance data of a scene, instead of just on-screen color values that normal bitmaps do. There are two good reasons for using HDRI in 3d and exploiting the special properties of HDR images - A. for producing realistic looking reflections and B. for lighting a scene (The 3D program converts the HDRI to lighting information).
Second, Lightprobes
Lightprobes are special HDR images. They are usually generated from photos of Steel or Chrome mirror balls set in the live environment. These photos are converted into HDR images. A great tool for that is HDRShop. This program can take multi pictures of a chrome ball, or a group of panoramic shots, and make a sinle HDRI lightprobe. It can all generate lighting information directly that can be imported into Maya. Good stuff!
Last, Reference Images
Lightprobes and HDRI can also be Reference Images. However, in it's simplest form, a reference image is simply a way to make sure the 3D looks as it should. A reference image can be the lightprobe, used to help ensure the right look, or a reference images could be a photo of a physical model, stuck in the live-action environment, used to double check how your 3D model is turning out. Just a few years ago, Reference Images were all they used. They would take a picture of the chrome ball, and then build one in the 3d program to match, adjusting lighting till it looked right. Making lightprobes that the 3D software can apply automatically is a new technology.
First, HDRI
HDRI stands for high dynamic range image - sometimes referred to as a radiance map. The dynamic range of a scene is the contrast ratio between its brightest and darkest parts. A HDR image therefore has a greater dynamic range than a standard image file such as a jpeg, tiff etc., which is a low dynamic range image. HDR images have the important property that their pixel values are proportional to the amount of light in the original environment where the HDRI was captured. So the benefit of the HDR format is that it stores the amount of luminance data of a scene, instead of just on-screen color values that normal bitmaps do. There are two good reasons for using HDRI in 3d and exploiting the special properties of HDR images - A. for producing realistic looking reflections and B. for lighting a scene (The 3D program converts the HDRI to lighting information).
Second, Lightprobes
Lightprobes are special HDR images. They are usually generated from photos of Steel or Chrome mirror balls set in the live environment. These photos are converted into HDR images. A great tool for that is HDRShop. This program can take multi pictures of a chrome ball, or a group of panoramic shots, and make a sinle HDRI lightprobe. It can all generate lighting information directly that can be imported into Maya. Good stuff!
Last, Reference Images
Lightprobes and HDRI can also be Reference Images. However, in it's simplest form, a reference image is simply a way to make sure the 3D looks as it should. A reference image can be the lightprobe, used to help ensure the right look, or a reference images could be a photo of a physical model, stuck in the live-action environment, used to double check how your 3D model is turning out. Just a few years ago, Reference Images were all they used. They would take a picture of the chrome ball, and then build one in the 3d program to match, adjusting lighting till it looked right. Making lightprobes that the 3D software can apply automatically is a new technology.
0 Comments:
Post a Comment
<< Home