Particle Positions Change During Rendering

[Byteman]

I'm trying to manually collide a SDeflector with 14 individual particles one by one to change their materials upon collision. I've done all the alignments and see materials changing in the viewports, but when I press the render button, all particles change positions and my collisions are no longer present until I stop the rendering and go on manipulating the scene.

After hours of trial and error it became apparent that the disabled Position Object operator in the image (Which you'll see the settings in the image) is responsible for the drastic shift in positions.

I have added another Position Object operator, this time using only Volume setting and no Surface Offest and Separation. Particles seem to be in a similar position with respect to each other, but still all shifts to the right about the size of a single spherical particle. 

This is a VR animation so I tried to render Perspective views, too. It is not about the camera. 

Any Ideas on how to get rid of this movement and why this happens?

This is the Max file just in case about 1.5 mb. Go forward in animation until frames 600 or so: 

https://forum.corona-renderer.com/index.php?action=dlattach;topic=32942.0;attach=146006

[Byteman]

I seem to have solved the issue by adding a Cache Disk operator. Viewport positions are recorded with the operator and collisions work ok., but I'm still curious about what is going on here. Is it just a bug or what?

[BenBisares · Accepted solution]

You need to have your "Integration Step" be the same for both Viewport and Render. If not the calculations will be done at different intervals and cause the difference you see.

[Byteman]

Thank you very much indeed. Integration Step solved the problem.🙂

[Byteman]

Hi once again,

I thought Integration Step parameter solved the position change issues, but it did and did not?!! I am somewhat baffled.

I have a deflector in the scene. I have aligned it to 12 of the particles one by one in Flow2. Starting around frame 700, the deflector moves to a particle, moving it to the next event upon collision, to change its material.

The deflector stays in that position for 2 seconds (as if the target is being locked) then moves to the next particle until the 12th particle changes color. I am marking 12 particles first.

In the second stage of the animation, at around 1850 I use the same method to shoot the particles. Again move the deflector to the particles and fire a super spray which looks at the deflector. Then my target particles Spawn at the right moment as if they explode.

I made the deflector alignments in the viewports. Alignments are correct in the viewports but all 12 particles are jumping to their new positions when rendering (-and back after rendering ends). The jumping is visible if you use interactive render window of the Corona renderer. 

The baffling point is;  the targetting and shooting stages were actually rendering just fine in correct alignments but the particles were shifting positions in between those stages during rendering. (May be due to the event at that stage)

When I changed the Integration step particles stopped changing positions throughout the entire animation -not fully rendered though- but there was a change from 1849-1850 and there is not. Particle positions are constant but not as in the viewport and the deflector doesn't collide. I tried half frame and frame integration step in both viewport and rendering but nothing changes.

I might have made some changes to the scene and attached the new file. I appreciate if you can have a time to look. 

Edit: I added the entire scene as there are two particles. Flow 1 Damarici might have an oparator (Keep apart) affecting the other particles. Don't know if it works but just added it once and forgot to remove.