How to translate this technique to Houdini?

[Netvudu]

Hi there. As I

[kubabuk]

any links? more info...?

[Netvudu]

sorry, getting dumber by the moment

Fake ray marching technique

[Andz]

1.5. In 3ds Max, create a material with a solid white color, that uses your popcorn image as Opacity Map. Drag this to the Material Static event in the Particle View.

The default shading for the materials in max is Phong, with 50% gray in difuse, ambinent and specular. So I guess he only changed the diffuse color to 255,255,255 and in the opacity slot, the popcorn map was added.

1.6. In the Material Editor, make sure the popcorn map is open. Click on "Bitmap", and select Mask from the Map Browser. Choose "Keep old map as sub-map" in the "Replace Map" dialog. In the new Mask material, your popcorn map is set as Map, so drag that do the Mask slot, and choose "Swap".

1.7. Click the Map slot, and choose Gradient Ramp from the Map Browser. Set Gradient Type to Radial. Right-click the left flag, choose "Edit properties" and change the color from black to white, right-click the center flag and choose "Delete", and right-click the right flag and choose "Edit properties."

Here he just added to procedurals over that popcorn texture, like a multiply one is a radial gradient to make the center of the popcorn more opaque then it's edges (this effect could be directly applied in them map in photoshop), the next texture is a smoke generator, just like a fractal turbulence, the only advantage if any in using this one is because is resolution independent, but i think it would look exactly the same in every single particle, so it still could be done directly in the same popcorn bitmap.

1.9. Create a Target Direct light in the top viewport, so it lights the teapot from behind, and place the target in the center of the teapot. On the light's "Intensity..." rollout, activate Use Far Attenuation, and adjust the Near and Far values so the range covers the whole teapot and the particles. Under Directional Parameters, adjust the Hotspot/Beam so all the particles are covered. Now for the magic: in the light's Advanced Settings rollout, click "Ambient Only". This will make the light ignore the polygons' angles, which is exactly what we want.

The only special thing in the light is that it is only contributing to the ambient part of the shader, so it doesn't matter which direction the particles are facing (probably billboard). The shading effect there comes from the lights falloff. So if you had 2 teapots in the scene you'd need one light for each teapot. If you have a lot of clouds hehe, you'd need a light for every cloud there.

If you need more help from other parts of the tutorial just ask ;-)

Edited October 14, 2008 by Andz