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## Popular Content

Showing most liked content on 03/05/2015 in all areas

1. 1 point

## How to calculate divergence of a vector in Volume VOP?

Have you tried making the laplacian calculation in a vop?
2. 1 point

## How to calculate divergence of a vector in Volume VOP?

I chopped my file from a fluid sim recreation in sops, but if you look at the formula for divergence you divide your sum of differences by 2*stepsize. I believe this comes from a need to have your final output be independent of your fluid resolution, though I don't know enough about descretizing pde equations to give a solid answer.
3. 1 point

## How to calculate divergence of a vector in Volume VOP?

Looks the same to me. Edited Raymonds hip a little, just inverted his solution and added VDB control. 100% match. divergence2.hip
4. 1 point

## Short and sweet OP centric lessons

I have created another short tutorial on how to alter the FLIP solver for correct Bullet Time emulation. You can view it here:
5. 1 point

## Suppress small Artefact in PBR render

Hey, here are a couple of things that I found helpful when working with mantra. 1. Set your min reflection ratio to 1. This helps in reducing artifacts because Houdini is not trying to be smart by reducing your secondary samples by an arbitrary amount (in this case 0.1) 2. Min Ray Samples needs to be higher than 1 if you want to get rid of artifacts but should not go much higher than 4 usually. It needs to be higher than 1 so Mantra has a certain amount of information to decide whether to sample more or not. 1 sample is not enough for that. 3. I found that upping the Pixel Samples is often more successful than increasing secondary ray samples. I suspect that this is due to the way mantras random number generator works. With a new pixel sample a new SID (sample ID) is generated which helps decreasing correlation artifacts and results in a more evenly spread sampling noise. In most cases you need to increase your pixel samples anyway when starting to work with textures and especially when Motion Blur or DOF enter the mix. 4. Primary noise that stems from insufficient 'shadow samples' can only be efficiently reduced by increasing light samples. Otherwise you have to go crazy with the rest of the sampling parameters. Try to use the diagnostic planes to identify the type of noise you are getting. The recent splitting of direct and indirect ray samples can also help to get rid of 'primary' noise. I hope this is helpful. One more thing: I believe the Maxwell voxelization step is just the generation of the raytracing acceleration structure (like mantras kd-tree) and has nothing to do with interpolation techniques a la Brickmaps. cheers, Dennis
6. 1 point

## How to calculate divergence of a vector in Volume VOP?

divergence.hip finite difference divergence, the difference of neighboring voxels, summed over all axes, regularized over the step size of the grid, from a cfd standpoint atleast. good fluids cheat sheet http://http.developer.nvidia.com/GPUGems/gpugems_ch38.html
7. 1 point

## How to calculate divergence of a vector in Volume VOP?

Have you examined the definition of divergence? From wikipedia, it looks like it's just the sum of the vector components of the gradient.
8. 1 point

## How is Emission calculated in Mantra Surface material?

The parameters are referenced using /mantrasurface/surfaceModel/subinput_opacity This node is a reference to all the parameters but only some are exposed on that instance for cleanliness ​With Ce/Emission exporting it as a variable makes it available as a pass (AOV) as well as emissive Emission illuminates objects is handled by making emission visible to secondary rays
9. 1 point

## Bullet solver and drag force

Also, note that in Houdini 14 the Bullet solver re-evaluates forces at each substep, so you can now increase the substeps on the Bullet solver instead of the entire DOP network if you have strong drag forces.
10. 1 point

## Create a line from randomly numbered points

Hi odForce! Haven't posted on here for years! I had to solve this exact problem on one of the Spider-Man movies where we needed a way for Spidey's webs to hit surfaces without getting twisted. We would project points representing the hit position of each thread in the web's terminating 'Eiffel tower' shape. You get a cloud of points scattered on the surface that isn't necessarily planar. The task is to fit a polygon to the points without getting twists. So I solved this by automatically calculating the best fit plane through the points and the centroid to give me an axis. Then I sorted the points by polar coordinates around this axis. If you then join the points you get an untwisted polygon. Pretty sure it worked every time.
11. 1 point

## make the float value always 4 digits

E.g. with hexpression (but this example works only for positive numbers): { in = fit01(fit(\$F,1,100,0,1),0.0,150.0); # input data digits = 4; # digits to display d = digits-strlen(int(in)); mult = 10^d; out = int(in*mult)/mult; # adjust tenths values return ifs(out==0,padzero(digits,out),out); # fix for 0 } pz_round_to_digits.hip
12. 1 point

## Short and sweet OP centric lessons

I have created another short tutorial on how to drive animation using sound. You can view it here:
13. 1 point

## Houdini procedural tree generator

I promised, that i will publish some source files and here they are. Inside you can find some network from demovideo, from pre work to render. All assets are unlocked(i used its for git), don't pay attention to that. Happy x-mas. Tree_generator_demoscene_unlocked.hipnc
14. 1 point

## Short and sweet OP centric lessons

Sure, here are a few links that are Houdini centric. I also have some Blender tutorials on Vimeo as well. Animated Crack Through Ground Plane: Shadow Matte Composite: Import A 2D Logo: How To Tech Sphere: These tutorials represent my steps in learning Houdini so if information is wrong or misleading please feel free to post comments with better or easier solutions.
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