Jan 25, 2021 16:00:00

Why do VFX artists, who are indispensable for making movies flashy, love shiny metal balls?

'VFX ', which is one of the indispensable elements in Hollywood movies, is used for various images, and if you are not an expert , you can completely distinguish whether it is a CG image or a live-action image. Is difficult . It seems that 'glittering spheres' are used at the shooting sites of videos using such VFX, and Vox has released a movie that approaches the reason.

Why visual effects artists love this shiny ball --YouTube


There are things that are indispensable for recent movies and videos that use VFX abundantly.

This glittering sphere can be purchased for about $ 20.99 (about 2200 yen). It is said that this sphere is the key to making VFX look more realistic.

Leo Bovell, who has worked in the movie industry for over 17 years, talks about the relationship between VFX and glowing spheres. He was the VFX supervisor for Hulu's popular original series, The Handmaid's

Tale.

A scene from the

Lincoln Memorial that appears in Season 3 of 'The Handmaid's Tale / Samurai no Monogatari'. In this scene, 'Destroyed President Lincoln' appears, and Mr. Bovell expressed this in VFX.

'In this scene, we basically had to replace the real Lincoln image with a 3D one,' Bovell said.

When asked by Vox Phil Edward, 'It's clear that we need to gather as much reference information as possible for this scene,' he said, 'That's right. In some cases, you may not be able to enter the scene between shoots, but that's because the scene is knocking down and you can't get in the way, 'Bovell replied. ..

One of the big problems faced with works that make heavy use of VFX, such as 'The Handmaid's Tale / Samurai no Monogatari' and the

Marvel Cinematic Universe , is that 'what you express in VFX' is in the real light of the day. The point is that you have to do it as if you were.

By realizing this, with the video actually shot ...

It becomes impossible to distinguish images using VFX. In other words, you will be able to create realistic images as if they were real.

The studio called

Mavericks VFX was actually in charge of the VFX for 'The Handmaid's Tale / Samurai no Monogatari'.

And what was used at the shooting site was a glittering sphere. The reason for using this sphere is 'HDR I'.

'HDRI' is

an abbreviation for high dynamic range image , and in recent years it has become easy to use as 'HDR' even with smartphone cameras such as the iPhone.

With the HDR function, you can take pictures with a high brightness range. The photo taken with HDR turned off is on the left, and the photo taken with HDR turned on is on the right. Since you can take pictures with a high brightness range, it is possible to leave more detailed information on areas that are extremely bright or dark.

The part surrounded by the white line is overexposed when shooting with HDR off, but the color of the sky is clearly expressed in the photo taken with HDR on.

Check how it changes with HDR on / off in another photo. When you take a normal landscape photo with HDR off, it looks like this.

The area around the sun, which is also the light source, is too bright and becomes pure white ...

The dark place deep in the forest is pitch black and the details cannot be captured.

However, when shooting with HDR, it looks like this.

You can see that the dark place can be photographed more finely than when HDR is off, and the trunk of the tree is firmly captured.

You can see that the outline of the sun is clearly reflected, and the shape of the cloud that has been blown out can be accurately expressed.

HDRI, which can be taken using the HDR function, is a picture generated so that it has a high brightness range by extracting information from pictures taken with different exposure degrees.

VFX uses HDRI to understand how light works during the scene.

In addition, if you can take a panoramic photo that covers 360 degrees, you will be able to simulate 'how light works' in every area of the photo. In other words, in order to make it easy to take a wide range of photographs, we are shooting a mirror-finished sphere.

Also, HDRI isn't just used to determine 'how to illuminate' the objects you add in VFX. When a new light source is added in VFX, it is also used to simulate how the light shines on everything in the scene.

Then Edward asked, 'How can HDRI help me when I have to add something using VFX away from the shooting date?'

'When you shoot an HDRI and enter information about the light in the field into your computer, you get immediate feedback,' said Bovell.

For example, when expressing marble with VFX, HDRI is very useful for realistically expressing the material and shadow of the material.

The reason why glittering spheres have been used to shoot HDRI is that you can easily generate 360-degree photos by putting the photos of these spheres in the appropriate software.

You can even create HDRIs for 360-degree photos by taking photos at any exposure.

There are other ways to take a 360-degree photo besides taking a glowing sphere. You can also rotate the camera to take panoramic photos or use the 360 degree camera. Not long ago, this method of using a glowing sphere seemed to be the standard, but Mr. Bovell said, 'I use the 360-degree camera

THETA . It's so small that it doesn't get in the way.'

Comparing each method for taking 360-degree photos, it looks like this. A method of shooting a shining sphere that ends overwhelmingly quickly. The highest quality is to rotate the camera to shoot.

By using the information about the light obtained from HDRI in the photo without the sphere, it is possible to illuminate the object created by 3DCG with realistic light. You can see that the objects added by VFX reflect trees and the sun, which is due to the benefits of shooting HDRI.

Such a 'method of shining light on a 3D object to make it look like it exists in the real world' was devised by researcher Paul Debevec in the 1990s.

In his treatise, Devevek said, 'Modern technology is too laborious to render 3D objects realistically, and it's hard to say that it's always successful,' VFX in the 1990s wasn't. It is said that it was efficient.

The method using HDRI was proposed as a method for illuminating 3D objects more easily and realistically than such a conventional method. And, in the paper, as a method for taking a wider range of HDRI, 'shooting a glowing sphere and generating a 360-degree picture' is mentioned.

It is now possible to easily simulate HDRI in a variety of environments, such as in old rooms or outside the cathedral. Still, there are many artists who take the trouble to take 360-degree photos and create HDRI with their own hands to illuminate 3D objects more realistically.