emit particule from texture

[Spyrogif]

here there,

i'm new at houdini and concentrate actually on particles.

Did you have any idea how i can control particules emitting with a texture.

I've understood the color to particules via pic() fonction but it's not what i need.

My goal is to create a grid who emits only where my texture is white (this is a black and white texture).

Of course i can plug my color informations to particules alpha with the pic fonction but it means unwanted compute time with the non alpha particules.

How can i send the pic() values into the Const birth rate of my source node ? (something like black=zero emitting white= Const birth rate value.

If you have any idea to help me

btw : Sorry for my bad english, i do my best !

[majikal]

hi...

one way is:

check this

http://www.sidefx.com/index.php?option=com_content&task=view&id=1030&Itemid=216

and

http://www.sidefx.com/index.php?option=com_content&task=view&id=1032&Itemid=216

insted of using brush you insert your picture and then emit from scattered points..

Edited September 23, 2009 by majikal

[Spyrogif]

i check this right know but the second link looks the good one...

thanks for the quick reply majikal

[Spyrogif]

what is the best way to replace the brush node by a texture ?

in the http://www.sidefx.co...1030&Itemid=216 the brush node override color and create a area attribute who is use by the scatter.

i'm not comfortable with attributes how can i tranform my Cd attribute to a area attributes ?

Edited September 23, 2009 by ndeewolfwood

[Spyrogif]

ok i've found a solution mixing different techniques found in older post. and it's good to go :-)

i start with my object> a uv node>a subdivide to get fine distribution>a VOPSOP to get the cd attribute (damnn it's so quick compare to pic() fonction)>a pop net

in the pop net i put a $Cr in the birth probability...and voila...

first time using the vopsop :whaaoo it's really cool and simple.