Hi!

I am using houdini from past 2 years. i want to create huge explosion of airplane in air. concept airplane is exploding by a bomb. i tried to animate the fuel amount and inefficiency amount, fuel speed and turbulence. but i am not getting the explosion effect(external force). fuel is spreading in all the axis but i am not happy with it. i am following the reference of Armageddon space ship explosion. i know that they use lots of layers of fire smoke and debris. but i am talking about overall look and force.


and in pyro shader if i am giving noise to the fire or smoke then when i render the hole scene i come to know that in certain frame range shader is flicking up. it looks odd.

so please help me on this.


Thank you

Hey guys i am facing the same flicker issue. To b precise its on frame 51-52 of fireball effect. Tried all combinations of noise even tried switching them off. In shader i used density as base for fire. i changed that to heat and temprature but no success. i even tried increasing the stepsize from 1 to 3. then i got the flicker one frame before!

Pleasse help. i used houdini 10.0.249 i believe.

System spec:
Intel Xeon 16 core processor (8 + hyper threading)
12 GB Ram
Quadro FX 3400 graphics

Talking about the flicker does not really help , posting up a test scene file that shows the problem and a QT is pretty handy to dissect the problem.

I would suggest you need to lower the step size below 1. Setting higher will just create larger steps as the ray marches through the shader which of course will cause you to loose detail and decrease render time.

r

hy guys here's an attachment of the .mov file of render. Its actually just the basic inbuilt preset settings. i did work a lot to build ma own blast but then checked back with preset if i was wrong…. the same flicker is in that too. its in the fire noise in shader i believe. please check and advice

thanks

rubens83
hy guys here's an attachment of the .mov file of render. Its actually just the basic inbuilt preset settings. i did work a lot to build ma own blast but then checked back with preset if i was wrong…. the same flicker is in that too. its in the fire noise in shader i believe. please check and advice

That looks like a rest position problem. Things to try:

1. Check that the shader's “Dual Rest” settings are the same as the simulation's. To do this, first go into your pyro DOP network (named “AutoDopNetwork” by default), select the “pyrosolver1” DOP, and look in the Advanced>RestField tab. The parameters “Initial Reset Frame” and Reset Every Frame“ control how the dual rest fields are staggered in time. These default to 1 and 50 respectively (they used to default to 1 and 20 I believe). Now look at the ”Settings“ tab of the pyro shader and set the ”Start Frame“ and ”Reset Rate“ parameters to match the DOP's ”Initial Reset Frame“ and ”Reset Every Frame“ parameters respectively. There's a default mismatch for the reset interval between the two (one defaults to 50 and the other one to 20, which is likely what's causing those noise jumps you're seeing).

2. Alternatively, a less desirable approach would be to set the ”Dual Rest" toggle of the pyro shader (in the Settings tab) to OFF. This should remove the noise popping, but it may also result in the noise features stretching over time (which is why the dual rest fields were created). Solution #1 is the better choice, assuming that your simulation is computing dual rest fields and that these fields (rest, and rest2) are indeed being sent to the shader (all of which should be fine if you used the shelf pyro tool, just make sure you're not accidentally deleting these fields in SOPs or anything like that).

Hope that helps,

Cheers.

Mario Marengo
That looks like a rest position problem. Things to try:

1. Check that the shader's “Dual Rest” settings are the same as the simulation's. To do this, first go into your pyro DOP network (named “AutoDopNetwork” by default), select the “pyrosolver1” DOP, and look in the Advanced>RestField tab. The parameters “Initial Reset Frame” and Reset Every Frame“ control how the dual rest fields are staggered in time. These default to 1 and 50 respectively (they used to default to 1 and 20 I believe). Now look at the ”Settings“ tab of the pyro shader and set the ”Start Frame“ and ”Reset Rate“ parameters to match the DOP's ”Initial Reset Frame“ and ”Reset Every Frame" parameters respectively. There's a default mismatch for the reset interval between the two (one defaults to 50 and the other one to 20, which is likely what's causing those noise jumps you're seeing).

Hey dude thanks a million. ur first step got me bang on da luks i was trying for a week now. I lukd up its help also to understand the same. But then i have a doubt. If i keep the reset field to default 50 wont it reset the field at that frame. but suppose my simulation is of 70 frames. shud i change 50 to 70 or let it be. And how does dual rest field work over da rest fields. Il be doin more RnD with those options tho. any assistance wud b highly appreciated!

Thanks

rubens83

Mario Marengo
Hey dude thanks a million. ur first step got me bang on da luks i was trying for a week now. I lukd up its help also to understand the same. But then i have a doubt. If i keep the reset field to default 50 wont it reset the field at that frame. but suppose my simulation is of 70 frames. shud i change 50 to 70 or let it be. And how does dual rest field work over da rest fields. Il be doin more RnD with those options tho. any assistance wud b highly appreciated!

The value of 50 for the reset rate means that there will be one rest position hand-off every 25 frames. The fields reset every 50 frames, but they're staggered in time – offset from each other by half the reset interval.

A rest position field behaves like other fields: it gets advected and pushed around by forces, etc. So what happens when you only have one rest position field is that, after a while, the initial values in the field (which represent a nicely arranged spatial lattice) will have gotten stretched and distorted away from their initial configuration; and depending on the simulation, this distortion may take many frames to become visually objectionable, or become apparent right away after only a few frames.

To solve this, the pyro sim generates two rest position fields instead of one:

Field 1 (rest) : +——————-+——————-+——————- (etc)
Field 2 (rest2): ———-+——————-+——————-+——— (etc)
At each ‘+’ in that graphic, the field resets (re-initializes itself with fresh rest positions). The shader then constantly cross-fades between the two fields, such that a given field has full contribution only at the reset frame (imagine a sine wave whose peaks and troughs touch each ‘+’ – that would be approximately how the shader moves between the two fields).
Also, you can see that even though the distance between the ‘+’ marks is the same for both fields (say 50 frames), the actual hand-offs happen at twice that frequency (every 25 frames).

So… long story short: If you see “stretch marks” in your noise, the reset rate is too long, so make it shorter. If it's set too short, you might start seeing “flickering” or “strobing” – that is, you might start to notice the interpolation, so make it longer. A value between 20 and 50 frames seems to work for most cases.

Hope that helps.

Mario Marengo

rubens83

Mario Marengo
Hey dude thanks a million. ur first step got me bang on da luks i was trying for a week now. I lukd up its help also to understand the same. But then i have a doubt. If i keep the reset field to default 50 wont it reset the field at that frame. but suppose my simulation is of 70 frames. shud i change 50 to 70 or let it be. And how does dual rest field work over da rest fields. Il be doin more RnD with those options tho. any assistance wud b highly appreciated!

The value of 50 for the reset rate means that there will be one rest position hand-off every 25 frames. The fields reset every 50 frames, but they're staggered in time – offset from each other by half the reset interval.

A rest position field behaves like other fields: it gets advected and pushed around by forces, etc. So what happens when you only have one rest position field is that, after a while, the initial values in the field (which represent a nicely arranged spatial lattice) will have gotten stretched and distorted away from their initial configuration; and depending on the simulation, this distortion may take many frames to become visually objectionable, or become apparent right away after only a few frames.

To solve this, the pyro sim generates two rest position fields instead of one:

Field 1 (rest) : +——————-+——————-+——————- (etc)
Field 2 (rest2): ———-+——————-+——————-+——— (etc)
At each ‘+’ in that graphic, the field resets (re-initializes itself with fresh rest positions). The shader then constantly cross-fades between the two fields, such that a given field has full contribution only at the reset frame (imagine a sine wave whose peaks and troughs touch each ‘+’ – that would be approximately how the shader moves between the two fields).
Also, you can see that even though the distance between the ‘+’ marks is the same for both fields (say 50 frames), the actual hand-offs happen at twice that frequency (every 25 frames).

So… long story short: If you see “stretch marks” in your noise, the reset rate is too long, so make it shorter. If it's set too short, you might start seeing “flickering” or “strobing” – that is, you might start to notice the interpolation, so make it longer. A value between 20 and 50 frames seems to work for most cases.

Hope that helps.

Wow dude thats a great n explainatory insight in da new untouched pyro Tool. Rest i had studied but this will definetly give me more control over my explosions.

hello, i was just curious about the initial reset frame and reset every frame on the pyrosolver and the complements in the VEX Pyro shader. I did quite a few tests and with a 24 fps, 120 frame animation… 1 and 50 as my values give me popping… but 1 and 60 do not… i'm curious is there some non-trial by error related way to figure out what these values should be? from your explanation it seems that 1 and 50 should work just fine but, at least for me, if i just run a default sim (flame), and change the values in the pyrosolver and the pyro shader, to match, at 1 and 50, i get the popping.

when i say default sim: i am referring to, create a sphere, click the “flame” pyro tool, and run the sim… without changing any parameters at all… and then in the pyro shader, changing the dual rest values to 1 and 50 like the defaults in the pyrosolver are… this gives me popping.

1 and 60 do not though

hello, i was just curious about the initial reset frame and reset every frame on the pyrosolver and the complements in the VEX Pyro shader. I did quite a few tests and with a 24 fps, 120 frame animation… 1 and 50 as my values give me popping… but 1 and 60 do not… i'm curious is there some non-trial by error related way to figure out what these values should be? from your explanation it seems that 1 and 50 should work just fine but, at least for me, if i just run a default sim (flame), and change the values in the pyrosolver and the pyro shader, to match, at 1 and 50, i get the popping.

when i say default sim: i am referring to, create a sphere, click the “flame” pyro tool, and run the sim… without changing any parameters at all… and then in the pyro shader, changing the dual rest values to 1 and 50 like the defaults in the pyrosolver are… this gives me popping.

1 and 60 do not though

itriix
hello, i was just curious about the initial reset frame and reset every frame on the pyrosolver and the complements in the VEX Pyro shader. I did quite a few tests and with a 24 fps, 120 frame animation… 1 and 50 as my values give me popping… but 1 and 60 do not… i'm curious is there some non-trial by error related way to figure out what these values should be? from your explanation it seems that 1 and 50 should work just fine but, at least for me, if i just run a default sim (flame), and change the values in the pyrosolver and the pyro shader, to match, at 1 and 50, i get the popping.

when i say default sim: i am referring to, create a sphere, click the “flame” pyro tool, and run the sim… without changing any parameters at all… and then in the pyro shader, changing the dual rest values to 1 and 50 like the defaults in the pyrosolver are… this gives me popping.

1 and 60 do not though

hey can u post ur hip file for reference. coz i have experimented over 120 frame n beyond n neva got a popup. u simply have to keep the values of pyro solver and shader same. i hope u r not animating them or sumthin!

rubens83
hey can u post ur hip file for reference. coz i have experimented over 120 frame n beyond n neva got a popup. u simply have to keep the values of pyro solver and shader same. i hope u r not animating them or sumthin!

hi there, sure i'll throw one together. but really all i'm doing is. create default sphere, click flames, add camera, add light, run lo res sim, run hi res sim, make sure that the vex pyro shader's dual rest paremeters match that of the pyrosolver's… *like you and i both mentioned already*… and then render. i get popping. the only thing i have done to fix this is, set my vex pyro start frame and reset frame and the pyrosolvers values, to 1 and 60 with a 24 fps 120 frame anim.

no animation on paremeters, no changing any values other than the dual rest params to match in the pyrosolver and the vex pyro shader. just to verify, you've tried everything straight up default and it works? with “flames”?? thanks

itriix
hi there, sure i'll throw one together. but really all i'm doing is. create default sphere, click flames, add camera, add light, run lo res sim, run hi res sim, make sure that the vex pyro shader's dual rest paremeters match that of the pyrosolver's… *like you and i both mentioned already*… and then render. i get popping. the only thing i have done to fix this is, set my vex pyro start frame and reset frame and the pyrosolvers values, to 1 and 60 with a 24 fps 120 frame anim.

no animation on paremeters, no changing any values other than the dual rest params to match in the pyrosolver and the vex pyro shader. just to verify, you've tried everything straight up default and it works? with “flames”?? thanks

hy sorry dude, cudnt reply b4 as ws on holiday
ok i checked again wd da settings u specified but its perfectly fyn for me. u sure ur rendering from a new mantra node not da default one!
please post your hip file dear