Pixel-Leggo-look in the beggining of Smoke Emition

[anthony_alvarez]

Hello. What parameter may be causing that look of the Blue-Area selected? that section of smoke have a "leggo" look, like cubes and it's very visible even in the render. The Smoke that is far from the source looks good already. Hopefully someone had this issue! thank you for reading this!

[georgi.zhekov]

Hey Anthony,

The pixel look is due to the grid resolution being very low. You will need to go to the Grid rollout and increase the grid resolution a few times.
Note that the larger grid resolution will lead to longer simulation times and larger memory consumption so you will need to be careful when you increase it.

Cheers!

[anthony_alvarez]

Hello Georgi!, thank you for your answer, and just to make it clear. you mean that i need to increase the size of the container? (x size, y size and z Size) or the Voxel Size (units)? Cuz I started with 0.2 and that was around 800K voxels. and then I increased to ~7MM and the effects was still the same :/ is that what u meant?

[anthony_alvarez]

Here is the example already with 7Millions of Voxels and still you can see the square-pattern in the emission. The second example is with 14.2Millions. there is not visible changed. Im not sure what it's causing this

[georgi.zhekov]

I meant the voxel size, but in your case it's a combination of both low grid resolution and the nature of how grid based simulations work.

In a grid simulation, the simulation container is divided into cells (voxels) that contain the fluid's properties (grid channels). The voxels are static pieces of space, and the fluid flows in and out of them, so with time the voxel's channels can change. Phoenix uses grid simulations for gaseous effects such as fire and smoke. Grid-based effects are contained within a rectangular grid and when you have curved objects such as the sphere you can start to see some voxelization artifacts.

In order to minimize these artifacts when you already have the grid resolution high enough you can do two things:

1 - You can smooth the smoke channel from the Input rollout. Select the Phoenix Simulator and go to the Input rollout, then in the Grid Channel Smoothing section enable the checkbox next to the channel you wish to smooth - in this case the Smoke. This will smooth out the blockiness you get, but will smooth out all of the detail out of the smoke as well. In order to smooth some parts of the smoke, but not everything - you can play around with the Threshold value - you can try setting it to 0.2 for example and adjust from there.

2 - You can fade out the Smoke opacity near the emitter so that the artifacts won't be visible. Select the Phoenix Simulator and go to the Rendering rollout. Then in the Smoke opacity options you can connect a V-Ray Distance texture in the texture slot, just below the Based On option and turn on the checkbox for the Modulate option. This way the Smoke opacity will multiply the Distance texture with the Smoke channel. In the Distance texture options you can add your emitter object (the sphere) in the Object set. After this by controlling the distance in the V-Ray distance texture options you can specify where the smoke will be visible and where it will be transparent. The Distance texture measures the distance between point and object and returns a black and white mask. Where the mask is white - the Smoke will be fully visible and where it's black - invisible.