Realistic Blood Works in Nuke -- Part I

 Hi guys,

Currently working on some blood works in a regional project obviously cant name it yet. 

The task is to mainly bring the gun flash, bullet wound, Blood splash, and stuff. Since I ve researched it for a long time, I ve got a bright viewpoint of how to add Blood in a shot realistically of hollywood quality.

As you know, I am a compositor and I use nuke for composting.

So, We can divide this into seperate elements...

1) Muzzle Flash

2) Blood Splash

3) Bullet Wound

4) Splash on Face and body

5) Impact on background

6) At last, minute details of wound.

So as of muzzle flash, What we are going to do is basically add a Light to the input 2 or 3 frames based on the supervisor or director. As of here my supervisor directed me to add for 3 frames.

For here, Lets just take this for an example to add lighting, Most of them what they do is basically just add the constant and blend it using the blend modes in merge node. But to get the realistic thing what we do is, just use a grade node and what we should do is take a luma keyer and just blend and get the highlights, whereas we use it as a mask. 

So This is what a mask may look like. If we just give a slight yellow tone using gamma, It would be perfect. For a Flash, For example The bullet starts at frame 1, So The lighting opacity should be at 1 in frame 1, .6 in frame 2, .25 in frame 3 and 0 in frame 4. So this is how get some realistic feel.

But To control the lighting depth wise, we have some cool techniques. Thats where we use the multiply mode and create a epicentre or impact point. 

So we just multiply the whole luma data to the mask we created using roto node to get a perfect depth wise lighting. So finally, we just need to animate it using a multiple node. And this is how I add a muzzle flash.

And for the final part, If we need any interaction with the background, we can just mask it, and give it a slight opacity.

So as we completed the muzzle flash part, just we keep it aside as we would add this as a top most layer.

For the next part, 

Is the blood splash,

We can divide this into different steps,

Blood splash

Blood mist

follow through impact on surroundings.

For blood splash, We do have a library, obviously you can get many things from internet and stuff.

So what we do is find the right element and place it at the epicentre. This is where it all begins,

This should start from frame 3. The size and the intensity depends on the supervisor and director, But mine just went on with my 1st version. 

Then as for the blood mist part, what we should do is, just same as that we will use a element from library or online,.

This is like a cheat code for many blood shots. blood mist just makes it more realistic.

This blood mist should start frame number 4.

 As for the last part which is the environmental part, there are several types to use here, for example, 

1) We should do the follow through of the bullet and blood behind the head

2) For the second part, we should affect the environment using blood.

In here, we should just time these elements with the splash and movement. 

For the main part, Matching the color is the most important. Whereas gain plays the main role for brightness and stuff, lift plays for intensity and gamma plays for color.

And for the splash thing to be more realistic, get the motion blur using a motion blur node, and we should use the epicentre technique here as well. but we use it for intensity, As the blood spreads as far from the impact point, Its intensity gets reduced but not to 0, like 0.5 to 0.7.

Key note -- Make Sure your blood element has lighting interactions in it.

Because, as far I believe the more it comes from 3D the more the quality.

When it comes to manual lighting there are different techniques which can be seen in other post. For now, we can get into the environmental touches.

In this project, There was a pipe behind the charecter and plain wall like thing.

So what I had to add splash element to the wall and do the same with the pipe. But here's Its a little bit different. To get the truthful visual effects, I had to use nodes like spherical transform, Vector distort etc.. to make the blood splash drip on a pipe.

We can see those tools later.

Bullet Wound:

1) Add the bullet wound element

2) Blood clot spread

3) Splash on face and body.

4) Opening of wound.

For the bullet wound element, imported from library matching the color and positioning is enough reality. 

But the clot spread needs to be more organic and real. This part should be a little bit darker than the wound as it is a clot, with zig zag edges whereas achieving this through grade node is best.

Splash on face and body is where we take this to next level, For this we can use a very useful tool known as keen tools. We can come into the keen tools part later. Blood splash on face was achieved by keen tools and on body was achieved using mocha's power mesh.

Well, It gave a wonderful Result.

Tracking:

Here is where we use keen tools.

Keen tools does a rotomation inside nuke whereas it produces a 3D model, and tracks the head wheareas I animated manually, since tracking issues.

Using this 3D model, we can project the splash and wound on the right position, So that the next level is achieved.

Please mark my words, The more in 3D, more the real.

Mocha pro power mesh is great for stuff like body parts and cloth type things.

Even we can use smart vectors for cloth, It ll be more helpful.

As once a great man said to me, The complete comp can only achieved by mixing a numerous number of techniques.

So the last part, The last minute details on the wound.

Well this was new for me too. My supervisor taught me to add this detail. what he said was wound doesn't appear at just 1 frame all of a sudden. But what we should do is jus we should is to create a tiny opening for 2 frames before the splash.

When, The bullet hole starts to grow.. The basic thing is to reduce the saturation.since it would have no color at the starting, jus use like .3 saturation of the wound.

My approach was basically keep the same wound but mask it with a roto shape, so that it looks like it grows as frame progresses.

The main thing is the wound does not look round, so we should just break the roto edge.

For the final wound thing, we should get the physics of a wound.

In here, 

The angle of the shooter determines the wound size and texture. if the shooter shoots from left. the dark part of wound should be on right. same vice versa, These are some minute details to make a comp look better.

So finally, This would look as hell as good after adding das grain.

Thank You,

See you at other post.