VAT Problem Solving

04/10/24

TIP AND TRICK: *** Note to VAT users, ---do not move the pivot---- otherwise the geo cannot read the texture properly and it off sets it, causing it to glitch.

My Mistake: Because of all of my vat imports, the pivot point was skewed, making it difficult to navigate. I wanted to move the pivot so that it was easier to move around. When I centered the pivot using the modeling tools within Unreal, it immediate broke the particles. I went through each level and thought I had lost my progress.

Issue: When I had centered the pivot point, it had changed it on an object level in the content folder. Because the texture geo was moved, it could not read the material/material instance correctly. That caused the glitching because it was trying to read down the texture, pin pointing each particle, but since it was offset, it was not reading the data in the correct orientation. As seen below, here are my VAT Particle geo. The geo is meant to look like the one selected, but the rest was offset.

Solution: [Reimport Base Mesh} button.

This fixes the issue as it reimports the mesh, resetting the pivot point. It was much less tedious than deleting and reimporting everything manually. Thank goodness.

What I learned: Optimization is important especially when software is not as robust as you want it to be

I found some work arounds of some of the houdini vat limitations.

One of the biggest challenges has been the Target Texture width limit. The Target Texture Width determines the texture size (1080, 2k, 4k, etc). The amount of particle sprites it can produce is dependent on the resolution of the texture. Luckily, the "Input Geometry Limit:" gives a number of the about of Points per Frame. The amount of points can not go over this limit or it will not export and it will error out.

Because I deal with particle systems that creates a high particle count that exceeds the maximum limit without customizing the texture width, I have to do some extra work arounds. If you attempt to pad the texture size to powers of 2 in order to try to customize and increase the resolution time, it will error out almost every time. It is not a perfect system.

Amount of points: 307,910

Maximum Points: 131,072

This was my solution: (The website crushes the quality )

I needed to separate out the particles and make sure they split evenly enough for the export to digest it. I could do a little math to know that it will split evenly into 3 parts so I split them and put them in their own groups. Then, from there I can clean up the particles, removing any unused attributes and groups, and export them without an issue.

The biggest setback is that it is tedious and and because there are multiple exports, it is all its separate textures and geometry that you need to import separately into Unreal.

Particle Count Issue

Whale and Fish Export

The particles exported smoothly, but the fish and whale was a whole other beast. The swarm for midterm progress report exported without too much of an issue, but when I tried exporting with the other fixed swarm and whale, it was missing some attributes that it needed to calculate the position of the point. It skipped every other frame. This is what a render would import as: