Additive Point Rendering...

[swampjesus]

Hello!

I recently decided to learn houdini, for particle rendering and animation.

When i saw the late Baily's work i thought i could give it a shot to teach myself how to code in c - so i have a quite hacked up opengl application what does strange attractors and whatever. So i decided to try to do it in houdini for educational purposes - i saw the lorenz attractor .otl stuff and studied it.

So, right now im just starting to do a particle vex script what generates the particles.

What would be the best way to get simple additive point rendering out of houdini? I understand that things work bit differently in strict opengl rendering using a buffer to plot points on etc - so should one try to drive every point through COPs what seems bit overshooting to me?

A test render from my opengl app so you can see what im looking after (it is just millions of points in 3d space with very low opacity and additive blending).

( *edit: hmm, im not sure if im in correct subforum maybe this is not shader related ... )

Edited August 7, 2007 by swampjesus

[swampjesus]

Allright - i will answer myself as the search button is invaluable:

by ihab >

" For color accumulation you can create a simple shader in vops that uses the particle colors. It can be a constant shader for example . If you do not premultiply the color with opacity in the shader and the opacity is less than 1 you'll have a color accumulation effect. Here's how to do it quickly.

1. go to vops and create a vex surface shader

2. MMB on the CF button in the output node and choose create parameter.

3. Rename the parameter name to clr (could be anything)

4.do the same with OF

5.create a shop from the vop you just created and set the opacity to .5

6. in your sops create an attibute (vector) and name it clr and set its value to $CR , $CG and $CB

7. attach the shader

VOILA!

cheers

"

[eunchae]

On 2007. 8. 7. at 10:36 PM, swampjesus said:

Allright - i will answer myself as the search button is invaluable:

by ihab >

" For color accumulation you can create a simple shader in vops that uses the particle colors. It can be a constant shader for example . If you do not premultiply the color with opacity in the shader and the opacity is less than 1 you'll have a color accumulation effect. Here's how to do it quickly.

1. go to vops and create a vex surface shader

2. MMB on the CF button in the output node and choose create parameter.

3. Rename the parameter name to clr (could be anything)

4.do the same with OF

5.create a shop from the vop you just created and set the opacity to .5

6. in your sops create an attibute (vector) and name it clr and set its value to $CR , $CG and $CB

7. attach the shader

VOILA!

cheers

"

Thank you!