Rendering HDR animation frames with 3DS Max Radiosity
When you render animation frames in 3DS Max, you may have difficulty adjusting exposure of the image frames
because the regular 24bit images (such as jpg, h.264) format exported from 3DS Max does not have enought
flexibility to bring up the proper exposure after rendering. The bright white spot/dark black spot may stay
without details even if you darken/brighton the image in Photoshop/Premiere once the frame is rendered in
3DS Max.
The Radiance .hdr format retains high dynamic range in a relatively compact file size (sill much
bigger than regular 24bit jpg files), and available
for exporting from 3DS Max. For instance, you can make HDR files from rendering in 3DS Max through
Radiosity (Advanced Lighting) or V-ray.
Reference (from Photography)
HDR images are usually made by photographic process by blending photos of multiple exposure and compressing them
by Tonal Mapping (instead of synthetically generating from computer graphics).
A good introduction about HDR photography is here.
(High Dynamic Range Photography at Cambridge in Colour)
Image Examples
3DS Max Radiosity images saved in .hdr format:
image1, image2
To view these images and adjust exposure dynamically, you can download the files and use either one of the following methods.
- openHDR viewer (Drag the image file to the page and use mouse wheel to adjust exposure)
- open the file in Photoshop, check Image>Mode>RGB Color>32bits/channel, and use Image>Adjustments>Exposure
Pipelines for animation application
In animations, it is often necessary to change the exposure of the camera to reveal/hide different parts of the scene.
Method 1: fixed Logarithmic Exposure and post-process in Premiere
- Use Logarithmic Exposure in 3DS Max rendering
- Save as jpg image frames
- The Logarithmic Exposure compresses a good range of luminosity to a regular image file (jpg). The image file retains
more details of the dark parts and bright parts of the scene in comparison to other Exposure options such as
Phyisical Camera Exposure, but the images look flat (less contrast) when they are rendered. However, if you use this method,
you can use Premiere/Photoshop filters to adjust Contrast/Brightness (LEVEL/EXpoare, etc) as post-rendering process.
- The range of post-rendering adjustment you can make are much wider than the result from Physical/Linear exposure, but is still limited.
Method 2: animate exposure levels directly in 3DS Max
- Animate exposure (Logarithmic Brightness/Contrast or Physical Camera EV) using key-framing method in 3DS Max
- Save as jpg image frames
- A very good planning and testing is needed before rendering.
- You can fine-tune the result by combining the rendered result with post-rendering process in Premiere/Photoshop as in Method 1.
Method 3: blend multi-path animations in Premiere
- Render animations of the same path a few times with different exposure levels in 3DS Max. For example, one path with higher exposrue
(for interior space), and another with lower exposure (for exterior space).
- Physical Camera Exposure Control is recommended to get good contrast (or use Logarithmic Exposure Control)
- Save an animation for each clip (that was made with a different exposure level). You can use h264/mp4 but using jpg image sequence
can retain higher quality and is recommended.
- In Premiere timeline, blend the animation clips to achieve a desired exposure. An easy way for blending is to control
the transparency of the clip placed in the upper channel in Premiere timeline. For instance, when the camera comes from outside
to instide, place the clip of higher exposure over the other clip of lower exposure, and animate the transparency of higher exposure
clip so that it is opaque outside and becomes transparent as the camera moves inside.
Method 4: use HDR image frames (.hdr for radiosity)
* 3DS Max encodes radiosity HDR rendering only into .hdr format. Other 16bit/32bit formats do not work with radiosity rendering (as of Max 2021).
Since Premiere does not read .hdr format (as of Adobe CC 2022), you need file conversion in Photoshop.
* If you are using Vray, you can use some of the 16bit/32bit format.
- Render animation with NO EXPOSURE CONTROL option (Rendering>Exposure Control) in 3DS Max
- Save image frames in .hdr format with NON-CLAMPED option (Be aware that the file size is much larger than .jpg.)
- In Photoshop, use batch method and convert all the .hdr image frames to .exr (OpenEXR) format. Then import the frames into Premiere.
- In Premiere, apply Lumetri Color Effects (Video Effects>Color Correction), and adjust Tone>Exposure (and perhaps White Blance>Temprature)
- Alternatively, recent versions of Aftereffects may import/handle .hdr files directly
