Controlling pyro fuel emission by texture map

[Strob]

Hi,

I want to emit fire from a geo and use a texture mapped on that geo to control the fire emission.

I know there is a way to scatter particles on a geo and then use a texture mapped on that geo to control those particles scale and then use them to emit fuel, but I would like to know if there is a way to directly use a texture on a geo emitting fire to control the fuel amount so when there is a gradient in the texture, the fire really fade correctly instead of just being emited by smaller particles in the grey areas... also I don't like the idea to have to use a really dense mesh to have enough rez for the texture to show in the scattered particles when there are finer details in the texture (or maybe Houdini is so powerful that it doesn't bother to do this...)

In the doc about the "attribute from map" node, we can read this:

http://www.sidefx.com/docs/houdini/nodes/sop/attribfrommap.html

You can use this node to create density, fuel, and temperature data to drive a fluid simulation. Using the Fluid Source operator, this data can become a set of volumes to be used as a source for a fluid simulation.

So by "fuel data" do they mean scattered particles as emiter? Or is there a way to use that node to directly control the fuel by a texture?

tanks in advance for any hint folks!

[3dome]

The docs also state:

Samples texture map information to a point attribute.

So whatever it reads from the texture map, it gets written onto points. So to keep detail from the map you need a high-res mesh/pointcloud.

Apart from that, Houdini will have far less problems (probably hardly any) to deal with the high point count in your scatter than with actually keeping that detail when building the fields in DOPs (=> voxelsize).

Edited November 6, 2018 by 3dome

[Strob]

Ok good.

In H17 it creates points anyway by default. we then just need a delete node with this expression:

tex(filename, U, V, color_type) > 0.1

for example:

tex("$HFS/houdini/pic/baconAlpha.jpg", $MAPU, $MAPV, l) > 0.1