Curling ray trace / black hole

[balthou1703]

Hello everyone,

I'm trying to set a blackhole effect like gargantua in Interstellar, in a low cost way.

The idea is to us a grid as a renderer, parented to a camera (sticked to its frustum), to send a ray from camera position, through the grid, to a sphere and if the ray sent is in the periphery of this sphere it curls/bend. I have found the script to do that in another software but I don't know how to get the global ray direction information and how to use it.

I thought use a snippet in a material to write the script and put the material on the grid.

 

Maybe it's not even the most relevant idea to do this effect. I'am open to other solutions

 

Don't know if I'm really understandable ^^'

Thank you anyway in advance

[Hazoc]

Hey

You could create a lens shader (http://mattebb.com/blog/weblog/houdini-fisheye-camera/) or then model your custom lens as an object. Here's a scene showing a sphere with a refracting material and soft edges acting as a mysterious ray bender.

distortion_field.hip

[balthou1703]

Thank you Hazoc,

it could be, indeed an other way to solve my problem, but it isn't exactly what I try to do, if you are familiar with "rayhit" and to use snippet in materialbuilder, I could send you a scene with the draft map script I'm trying to create?

 

Regards

[Hazoc]

Sure! I can take a look.

[StepbyStepVFX]

Hi,

I wanted to do exactly the same thing when I would have some time. My idea was to do it in VEX in SOP context, inspired by what this guy has done (he shared his file) : 

I would have used a volume to bend the ray progressively as it is going forward, and using gravity to do it (you calculate a force % to 1/Distance^2 to the black hole). My idea was to replicate a gravitational lens effect :-) But did not have time to start.

Let us know what you are obtaining with your technique !

[balthou1703]

Hello again Hazoc,

Sorry for the delay, hard week for me : here is a first scene, pretty raw, where I have a sphere (symbolizing the black hole, will be black), a null and a plane parented to the camera: this plane is receiving the blackhole shader.

you will find in the material tab a material_builder with a simple snippet: the script is in it, but I don't know in Houdini what to link to what.

Hope you'll find out

 

thank you in advance

 

 

snippet_blackhole_shader.hip

[Hazoc]

It's impossible to exactly tell what you were after for here just by looking at an unfinished shader that doesn't even try to return any value. Maybe if you can draw a concept picture what the effect is exactly supposed to look like people could propose techniques to achieve the desired effect.

[balthou1703]

I'm trying to achieve this effect

https://www.shadertoy.com/view/lstSRS

bh.exr

Edited September 14, 2018 by balthou1703
copyright

[Hazoc]

I think particles would be the way to go for me with that one.