In this tutorial you will learn how to use FumeFX Geometry Source and FFX Vertex Paint to manually set velocity vectors on the source geometry.
In 3ds Max, select File->Open, and from your /Scenes/FumeFX/ Tutorials folder, select the file Tut_16_start.max.
Select Plane001 and from the Modifier List select FFXVertexPaint.
This modifier will allow you to paint velocity vectors and store them inside the Vertex Color channel.
Once the modifier is applied, you will notice that it will draw vectors for each face. For a better view switch the Perspective viewport from Wireframe to Realistic.
On the Vertex Color Paint rollout click on the Reset Color button - this will reset vertex color channel on the object by setting colors to gray. Gray color means zero for each of the X,Y,Z normal components.
Press the paint button and paint on the plane. Make sure that your brush stroke is long and continuous so that the paint tool can properly compute per-vertex vector and store as a color. After you're done painting, uncheck the paint button.
Select the FFX Object Src001 and from its interface pick Plane 001.
Scroll down to the Velocity Normal Map. Open the 3ds max Material editor and drag and drop Map #3 to the Normal Velocity Map channel.
Drag and drop the same map to the Color channel Map slot and change the Color Type from Disable to Set.
This Geometry Source will emit smoke all over the plane geometry and its color will depend on the color of the Vertex Color channel.
However, we want the smoke to exist only where we have drawn velocities to form a stream. For this task we will use Effector.
Select the FFX Effector001 Effector and look at its parameters.
We have named it "killsmoke" and its test conditions will be true for colors that are between 120 and 130. Gray vertex color on the grid is 125,125,125 and it is located on the area that we didn't touch with the brush. On those spots, all the smoke will be deleted.
Select the FumeFX001, open the sim tab and scroll down to the Smoke Master Effector.
Click on it and select "killsmoke".
This will connect Effector with the Smoke Master Channel.
Run the simulation.
Smoke will flow along the path you have painted. You might notice a slightly "blocky" appearance on the edges of the flow. This can be smoothed out by increasing the number of Plane segments.