Houdini Roadmap #2

[UPDATE - 26/03/2025]

Got my render materials to work, but I still need to work on the timing:

_____________________________________ _____________________________________

This week we're doing RBD Simulations The concept of the project is to have a forklift thrown at some crates with fruits in them. To start off I created the room geometry and mapped some textures:

Room Geometry for use as collision

Room geometry node network

With free brick and concrete textures, I was able to use LABS Auto UV and UV layout to map the texture to the walls.

After the room geometry was done, it was time to simulate the forklift using RBD bullet solver and the room as collision geometry.

INITIAL FORKLIFT SIMULATION

This is the initial result of the simulation:

The key lessons and takeaway from creating this network is:

• You should turn OFF "time dependancy" when caching your geometry data IF it does not contain any keyframe or animation data (such as transforms and rotates), because that will mess with your simulation. In my case, it froze the forklift Mid-air

  
  

• You should always be CONSISTENT with your merge nodes. For example, if you want to merge a cube and a sphere with the proxy of the cube and the sphere, make sure you have both merge orders for the main geometry and proxy geometry exactly the same.
  

• You can RIGHT - CLICK -> ACTIONS -> CREATE REFERENCE COPY to create a reference of any node you want that actively updates in real-time if the master node changes. How cool is that!

VEX WRANGLES

Moving on to what I learnt in VEX, the wrangle that makes the simulation work changes the geometry from animated to active according to the frame. For that I initialised the "animated" and "active" functions, then used the IF function to specify the frame: int @active = 0;

int @animated = 1;

if(@Frame>=10)

{

@active = 1;

@animated = 0;

}

I also learnt to control the velocity according to the frame: if(@Frame>=10)

{

@v = fit(@Frame,1, 75, set(0,0,40), set(0,0,0));

I connected the lines of code to the network using an "attribute wrangle" node.

In later sections, I was able to learn and use the RE_FIND and itoa functions to reference name attributes.

CRATE AND FRUIT SIMULATIONS

To start, we loaded up a free asset of a crate, then created a proxy geometry using the CURVE tool

Crate Asset

Crate Proxy

By combining the crate geometry with the proxy geometry. I was able to use copytopoints to the crates onto the location of a grid object that I created and used the edit tool to crate some variation:

Crate stack

To add some fruit, I was taught to use POINTS FROM VOLUME to put the fruits in a geometry and use an RBD BULLET SOLVER to simulate dropping them into the crates, using the crate object as collision geometry. Then bringing it over to the main network through an object merge. The simulation result, with the forklift and room as collision geometry:

PUTTING IT ALL TOGETHER AND PERSONAL TOUCH

To add to this assignment, I wanted to retime the scene and create a "freeze frame" with a moving camera. I also wanted to "mix" the fruit in the basket and bot just have each crate with one type of fruit, but that create a problem during material assignment as I did not give them all unique names. So putting the forklift and crate simulation together using an object merge, and retiming it, this is the render result (with the material bug) :

KEY PROBLEMS:

• I was unsure why the textures of the forklift, crates and fruits were not coming through, but if I were to disable the fruits, the crates and forklift gets the textures back. That is something I will have to work on during spare time in future weeks.

KEY TAKEAWAYS:

• You should always make use of unique name attributes to be able to reference every single geometry to part of your network clearly.

• Creating reference points with Nulls and using an object merge is a great way to transfer a section of a network into another network.

• The RBD Bullet solver will try to hold your hand alot, creating name attributes if you don't have one, packing an object for you if you didn't. Just make sure you specifically set the network up to ensure the RBD bullet solver doesn't do anything you don't want.

  
  
  
  

And that concludes this week! I will keep this post update if anything related to this project changes or I manage to fix the bug! Next week I wil finally be trying out Smoke and Pyro, I've always wanted to create a "ghost rider" type character with a flaming head. Can't wait to see how it goes.