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Rendering with Arnold in Maya using the MtoA plug-in.
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Arnold & Particle Flow

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Message 1 of 11
todd21st
467 Views, 10 Replies

Arnold & Particle Flow

In the past, in 3ds Max, when looking to change a particle's color or opacity over time you would just use a Particle Age map. Now that Arnold has been introduced does anyone know how to accomplish this? It seems Arnold and the Particle Age map are not working together.

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Message 2 of 11
madsd
in reply to: todd21st

Use either an OSL node calling attribute "paLife" or use an arnold User data node can call "paLife" in the string field. That will return the age, you can then scale it with a range node, or a CC node to move the time and spectrum around like you want.

Message 3 of 11
todd21st
in reply to: todd21st

Appreciate the response. Here is a link to the scene I'm working with...

Rocks & Smoke

Saved in 3ds Max 2019. I'm a bit new to these user data nodes that call attributes. And I'm definitely lost when you mentioned scaling it with a range node.

I am interested in how this works. What I'm trying to accomplish is having the trailing smoke form the rocks fade over the life of the particles. So at birth the smoke would be 100% opaque, at 50% of their life the smoke would be 50% transparent, and then finally at the end of the particles life the smoke would be 100% transparent.

I'd be super grateful if you could take a look at the sample scene above and show me the proper way to set this up.

Message 4 of 11
todd21st
in reply to: todd21st

The link for some reason did not display above. Let me try this...

https://we.tl/t-lXv3Jhc6Hp

Message 5 of 11
madsd
in reply to: todd21st

If you want to do some stepping, you can use 3 triggers from same feed, first spread the same life to 3 float nodes and scale them and position them on the timeline.
You need to add them up afterwards and combine the stream with add nodes for example.

paLife ---> a float node, another float node, a third float node.
"do things to all 3, retime, set gradient strength"
Collect with an add node, pipe a float into the add node and the another float into it as well, and add the 3rd to a new add node and add the combined add to that and use that as a mask.
For example.

Video to both solutions

Message 6 of 11
madsd
in reply to: todd21st

Did you check out the video I did?

Message 7 of 11
todd21st
in reply to: todd21st

Got a chance to check it out this morning. Thank you for taking the time to record and send that. Starting to make more sense now. The User Data RGB calls the paLife attribute then it's adjusted by using the Range node. This is working well to control the opacity of the smoke. Wanted to show you what I set up and see if this is the correct way to add a map to that pipeline;

3927-smoke-opacity.jpg

The smoke map is turned to B&W and used as the base color. Then the only way I could think to combine the color map nodes and the particle age opacity map was to use another color correct node. Where the color information is the input and the particle age pipeline is used at the mask. The invert is placed in there to make the particles white at first and black at the end for the mask. This seemed to work. Is this the best way to set it up?

Also, how would I use the calling of the particle age to control the particle colors over time? Like using the particle age combined with a gradient ramp so that the particles at birth are red, then turn to green and then blue. I'm slowly understanding how all these nodes come together but I can not figure out how to incorporate a gradient ramp node with the particle age node for the base color.

Message 8 of 11
madsd
in reply to: todd21st

Message 9 of 11
todd21st
in reply to: todd21st

Thank you again for your help on this. So far those two videos you've made have really helped in understanding how to access and manipulate the paLife parameter.
Just out of curiosity where are you located? Do you work for an animation company?
Also, where did you learn all this from? Experience or do you teach a class? Maybe you could recommend a learning resource for advanced level Arnold concepts.
Again, really appreciate your help!

Message 10 of 11
madsd
in reply to: todd21st

I am located in Denmark, and don't work for anyone, I spend most of my time helping people and do free stuff, once in a while Autodesk gives me a job to do something related to new features. Sometimes it's enough to pay the bills sometimes it is not.
Taught myself how to solve problems in general by being analytic and constructive, but I dont earn any money by doing so.

I dont know any classes, I could probably make some.

Message 11 of 11
todd21st
in reply to: madsd

shame you don't get paid for your efforts cause you definitely have a knack for arnold and 3d Max. glad to have ran into you on here. i'm sure our path's will cross again as i venture further into the Arnold realm! thanks again!

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