Particles from texture

Forums Technical Discussion Particles from texture

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martindisenio: Member; 8 posts; Joined: Jan. 2008; Offline

May 7, 2008 8:49 p.m.

Hi guys!

This is mi first post here, and im new with Houdini; because I have a easy question:

How to emit particles from a image texture / map channel ??

Its easy, no?
but, I don´t know how.

thanks!


AlvinYap: Member; 56 posts; Joined: March 2007; Offline

May 7, 2008 10:05 p.m.

See if this helps? I'm using the point expression to get the color from a COPs image map. I'd like to know if there's a way to use a low res poly to emit a high res image too!

Alvin

Attachments:
pictureEmission.hip (49.5 KB)


martindisenio: Member; 8 posts; Joined: Jan. 2008; Offline

May 9, 2008 10:17 a.m.

thanks for reply AlvinYap,
but, there is not my question.

What I need Know is how emit particles from a specific chanel of a texture.
i.e.: if american flag is my texture, them the particles born only from a red bars and not in the other areas.
Right?

If somebody help my , realy thanks.


stevenong: Member; 1631 posts; Joined: July 2005; Offline

May 9, 2008 11:18 a.m.

Hi,

I used Alvin's hip file for my example. The only difference is using the Birth Probability parameters in the Source POP. I used $CR as the criteria.

Cheers!
steven

Attachments:
pictureemission_birth_probability.zip (17.2 KB)


martindisenio: Member; 8 posts; Joined: Jan. 2008; Offline

May 10, 2008 8:37 p.m.

yea! something else.

thank you very much.


martindisenio: Member; 8 posts; Joined: Jan. 2008; Offline

May 29, 2008 10:51 a.m.

sorry, but, one more question:

This emitter system emits from the vertex, to do so i need to use a high res polygon mesh and with this the scene becomes increidibly heavy and difficult to work with.

Is it posible to use a channel of the texture, independently from the vertexs of the polygon mesh?

Please please pretty please help me out that i´m on fire.

Thanks in advance


Allegro: Member; 696 posts; Joined: March 2006; Offline

May 29, 2008 11:45 a.m.

you should be able to scatter (use the scatter sop) on the geometry and inherit the uv's. Should be more efficient than subdividing the geo

Stephen Tucker
VFXTD


martindisenio: Member; 8 posts; Joined: Jan. 2008; Offline

May 29, 2008 9:12 p.m.

thanks Allegro, but the trouble with the scatter SOP is that not copy the vertex color , and because that, I don´t make a group with the new points.

or , I don´t stand ´u how use the scatter SOP.


symek: Member; 1390 posts; Joined: July 2005; Offline

May 30, 2008 4:48 a.m.

martindisenio
thanks Allegro, but the trouble with the scatter SOP is that not copy the vertex color , and because that, I don´t make a group with the new points.
or , I don´t stand ´u how use the scatter SOP.

I doesn't but you can color it after

. Another scenario is to transfer this attribute with AttributeTransfer SOP, or even using VOPs with Point cloud method.

Here we have the scene with scatterSOP put *before coloring. If it won't work for you, just let us know!

cheers,
Simon.

Attachments:
pictureemission_birth_probability_colorscattered.zip (17.3 KB)

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