This shot was a set extension shot of a live action footage. It was 3D tracked Nuke and exported to Maya and Houdini for assets modeling and effect simulation.
I was responsible for all aspects except for the footage used in this shot.
I will try to breakdown this shot in detail in this post. If you have any question, feel free to reach out, you can find my contact info in my profile.
*If you don't see the videos below playing, please check the autoplay settings on your browser.
Preparation
Unlike my other projects, this one actually started in Nuke. I got this hand held footage from other people.
Upon import, because I was using ACES 1.2 as my system environment variable, I needed to set my input transform correctly first to view the right color.
I did a distortion analysis and a camera track to the footage, and then created a 3D scene in Nuke.
And then I put a card on the windows position to validate if the track was accurate.
When I was happy with the track, I put down a pointcloud generator to extract the geometry approximation of the scene.
And then I exported the pointcloud and the camera as a fbx file and brought them into Maya for modeling before transferred to Houdini for effects.
Simulation
The explosion was an Axiom simulation. it was actually my first time using it, and since then I've been keep using it. It was very fast and intuitive to use. The emitter was just some points with noised up velocity. But I only rasterized density for the source because I wanted to have a delay kick of fire coming out. So I made the temperature came in as an influence field a few frames after the density.
In the solver, I animated the disturbance, turbulence settings to achieve the look I wanted. And my combustion settings were set up that almost all the fuels ignited when the temperature came in.
And then I moved on to RBD simulation.
There were 2 parts I fractured, wood and glass. I was using the RBD material fracture SOP tool with wood and glass presets.
I was using SOP bullet solvers for RBD simulation as well. I used a geometry VOP to sample nearpoint velocity from the emitters and then scaled it up before added it back to the force attribute. And I blasted the parts that were flying out too far to avoid unnecessary calculation.
If I were to redo this, I would probably just advect them by volume which probably makes more sense and intuitive.
The result was a bit extreme and stylized; maybe not the most realistic. I think they might be flying out too far from the windows.
But those were all the CG elements in this shot.
Rendering
This shot was rendering in Solaris with Karma CPU mostly. I downloaded an Hdri from polyhaven that looked similar to the back ground footage and added some fill light to match it. And the element in this scene ware all moving quite fast, hence velocity blur were enabled. But I think the explosion was probably the only one that needed it.
The proxy building geometry was configured as matte in holdout mode.
Since this shot was undistorted in Nuke before 3D track. I would need to re-distort the render before compositing it back to the original video. I applied an over scan on the render camera.
Compositing
The rendered sequence then went back in Nuke for compositing. I reapplied the lens distortion and reformatted it back to correct resolution. Below is just the demonstration, of course it also needed to went through AOV gradings and corrections first before merging back to the node tree.
I also rendered the shadow pass AOV and used it as a mask to do some more exposure correction to tie things together. And that's all to it for compositing.
Final Result
Thanks for reading the breakdown blog. If you have any question or suggestion, please let me know. And if you find this helpful or interesting, please consider checking out my other breakdown, you can find them on my profile. Cheers.