mapping vector blur

[dan_j]

Hi guys,

I'm working on some trail effects and am just wondering if any one would like to share how I can map vector blur using a gradient to effect my particle/geometry. Peter Claes talks about it in the 3d buzz technical effects dvd and Aearon has used it in his invasion project, I know that its using the point sop to add the velocity attribute but then i'm drawing a blank! Any help would be much appreciated

Thanks

trail_blur.hip

[dan_j]

anyone....anyone?..........Bueller??

[Aearon]

hey there,

i'm not 100% what you mean by gradient, but i'm guess you want to blur it over time?

first of all here are some things i observed:

you are using $VX, but you don't really have any velocities to begin with. if you display the vector attribute in the viewport you will see that because of this all your velocities pointing to +X.

also you have the point sop at a stage where you just have polygon line. you probably want to put that just before OUTPUT so it gets applied for every point in the tube use something like $AGE * $NX * 10 respectively for each field. this will blur the geometry outward in every direction, with the blur increasing with age.

you can also add a ramp to the point sop and control the gradient based on that. so the expression would be something like chramp("blurramp",$AGE,0) * $NX * 10 assuming that you name the ramp "blurramp"

now there's another little problem with your setup... the sweep sop doesn't properly inherit attributes so you lose $AGE and most of your other attribs except v and Cd along the way...

it's getting a bit complicated to explain so i attached a hip file. in there i did all the stuff described above and also added a blurvalue attribute that increases from 0 to 1 based on primitive numbers, just after the sweep sop. it's not so nice but a simple workaround for the sweep problem. a better way would be to use a copy sop with proper normals setup on the line, as the copy sop can properly inherit all attributes. also the sweep sop has a lot of speed problems so i'd advise against it for heavy scenes. cook times seem to increase exponentially with the number of points.

trail_blurgradient.hipnc

[dan_j]

Hi Aearon, thanks for you help on this. I'll take a look at your file and see what i can learn from your tips.

Thanks again