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gillsp

WaterFall Scale

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Hi, I have been having struggles on how to make the right scale on a personal project. The setup is in the file. Basically is a waterfall running down a mountain(34 meters tall), somehow I think either my texture is giving a mountain bigger scale feeling or somewhat, the scale of the waterfall is not right(too fast).  I have tried the mass scale and spatial scale, both gave me very little results that is hardly notiable. The only thing seems to work is timescale of 0.5 or reducing gravity, but the reducing gravity is not ideal in any case because it doesn't look right. Adjusting time scale is just like being in slow motion though.

 

My question is how can I only adjust to speed of the running down waterfall without changing gravity or something else.(the emitter emits another flip), the targeted speed  of the runoff is about half or 2/3 of the current simluation, without changing the overlook of the waterbed. 

 

Obj:

 

https://drive.google.com/file/d/0B0-QsiyptV2gTFFpN0Q1QXNGTVk/view?usp=sharing

setupv5highopttestv2.hip

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Ok so the scene was a little to heavey for me to quickly 'see' what you meant by moving too fast. But the first couple things i noticed were:

 

- You have no friction on the fluidObject, this may have slow the fluid as it move down the hill/mountain. 

- you can try using a bit of viscosity as well (attribute transfer from ground)

- play with the time scale and forces amount because the scene is not really at scale (it seems)

 

 

Does this help?

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Hi, sorry I was at work. Let me try adding viscosity and frictin to see if that help. Well, the moutain is at a right scale of 34 meters tall, it's just maybe the texture of it is giving it a look of larger which makes the whole simulation looks small scale, perhaps the simulation is at right scale. But anyways, I did a test on  timescale, I think it works better, though I am not sure if that is what I want to do. Im doing tests on viscosity and friction, see if those can help. Thanks.

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I just did some quick test, didn't seem to work, unless I have to push the values to some extreme(100 or 1000), but viscosity is a number that I don't really want to mess with because it will give weird simulation than water I think, as honey or mud. The best bet now is timescale.

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Although I haven't looked at your sim (maybe a video would help for people who don't have a copy of Houdini at hand), you should free your mind from the idea of Houdini (or any other VFX simulation software) being a real physical simulator. It is a mini world using hypothetical, largely simplified physics that are optimized in order to look correct even though the behaviour might be far from real world behaviour. 

 

Forces like gravity, scale and paramters like viscosity are like suggestions and it is up to you to alter this hypothetical miniworld in order to make things work in order to create the final images you have in mind.

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Although I haven't looked at your sim (maybe a video would help for people who don't have a copy of Houdini at hand), you should free your mind from the idea of Houdini (or any other VFX simulation software) being a real physical simulator. It is a mini world using hypothetical, largely simplified physics that are optimized in order to look correct even though the behaviour might be far from real world behaviour. 

 

Forces like gravity, scale and paramters like viscosity are like suggestions and it is up to you to alter this hypothetical miniworld in order to make things work in order to create the final images you have in mind.

 

 

Not sure what you mean. If you run a higher-enough resolution sim you can simulate a lot of the real world.

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Hi everyone, looks like timescale does the trick:

 

https://drive.google.com/file/d/0B0-QsiyptV2gWWh4M3J0eVdwZ1dRTWcwSE5RVGxEdzZKT0Vv/view?usp=sharing

 

However, because I want more break up of the fall, and the geometry of mine is a mountain that doesn't have any boundaries to control the fluids. So it tends to be thin and spreaded out. I tried to get more volume in it, but this is the highest detail I can get. (0.1 separation, 32GB ram, around 40mil particles at first frame, 0.09 will give me memory error on later frames).

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Glad you are getting some results, is there anyway you can break the sim up in smaller pieces? you sim is pretty large (if I understand the scale correctly). You also will want some controlling forces/geo/volumes. 

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Well, the thing about breaking it into two sims is the collision between them. In houdini it doesn't allow you to have two different fluid objects that collide with each other, right?

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Well, the thing about breaking it into two sims is the collision between them. In houdini it doesn't allow you to have two different fluid objects that collide with each other, right?

This is true for the most part their our 'trick's and things you can do to fake it but the biggest thing I noticed was the size of your bottom basin where the fluid flows to is really really large, considering where the interaction is happening. You could shrink that down.

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