PRT Retiming with interpolate Sub-Frames

Discussion and Support of Krakatoa Volumetric Particle Rendering, Manipulation and Management Toolkit
LeePuznowski
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Joined: Wed Jun 29, 2016 8:20 am

Re: PRT Retiming with interpolate Sub-Frames

Postby LeePuznowski » Tue Feb 06, 2018 3:16 pm

Whew, I need to take a breath after that one :) Thanks for the full rundown. For this project, I'm perfectly happy with no rotation at all. I've simply set up Frost with an orientation divergence of 50 to give the particles some randomness. But even then, some frames were sporadically rotating, so I assume this is related to your explanation? Is there at least a way to keep the particles from rotating during a sequence but still maintain an initial random orientation? Maybe there's a way to simulate the particles from Realflow out with the necessary channels/information ?

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Bobo
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Re: PRT Retiming with interpolate Sub-Frames

Postby Bobo » Wed Feb 07, 2018 12:08 am

LeePuznowski wrote:Whew, I need to take a breath after that one :) Thanks for the full rundown. For this project, I'm perfectly happy with no rotation at all. I've simply set up Frost with an orientation divergence of 50 to give the particles some randomness. But even then, some frames were sporadically rotating, so I assume this is related to your explanation? Is there at least a way to keep the particles from rotating during a sequence but still maintain an initial random orientation? Maybe there's a way to simulate the particles from Realflow out with the necessary channels/information ?


What is the Orientation channel in Frost based on?
If you select some vector channel like Velocity, Frost has to build a matrix using that vector as Z. It needs to figure out the two other axes orthogonal to the vector. So it takes the Vector Cross Product with the up vector [0,0,1] to produce the X, and then the result get crossed with the reference vector again to produce the Y. As the angle between the reference vector and the up vector changes, you might get some adjustments in the resulting matrix, and a Divergence on top of it could cause surprising results.

You can select "Specify Orientation" which ensures the same fixed base value for every particle. Then you can set the Divergence relative to that. As the particles move around, they will never change orientation. However, they won't follow the Velocity either, so that behavior might be unwanted...
Borislav "Bobo" Petrov
Product Specialist
Thinkbox Software Inc.

LeePuznowski
Posts: 7
Joined: Wed Jun 29, 2016 8:20 am

Re: PRT Retiming with interpolate Sub-Frames

Postby LeePuznowski » Wed Feb 07, 2018 3:23 am

It's already at Specify Orientation with x,y,z all at 0 and a Divergence of 50 with a Custom Geometry for the Particle Geometry.


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