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A stream particle animation is useful for visualizing the flow direction and speed of a vector field. The "particles" (represented by any of the line markers) trace the flow along a particular stream line. The speed of each particle in the animation is proportional to the magnitude of the vector field at any given point along the stream line.
This example determines the region of the volume to plot by specifying the appropriate starting points. In this case, the stream plots begin at x = 100 and y spans 20 to 50 in the z = 5 plane, which is not the full volume bounds.
load wind [sx sy sz] = meshgrid(100,20:2:50,5);
verts = stream3(x,y,z,u,v,w,sx,sy,sz); sl = streamline(verts);
While all the stream lines start in the z = 5 plane, the values of some spiral down to lower values. The following settings provide a clear view of the animation:
The viewpoint (view) selected shows both the plane containing most stream lines and the spiral.
Selecting a data aspect ratio (daspect) of [2 2 0.125] provides greater resolution in the z-direction to make the stream particles more easily visible in the spiral.
view(-10.5,18) daspect([2 2 0.125]) axis tight; box on
Determine the vertices along the stream line where a particle should be drawn. The interpstreamspeed function returns this data based on the stream line vertices and the speed of the vector data. This example scales the velocities by 0.05 to increase the number of interpolated vertices.
Set the axes DrawMode property to fast so the animation will run faster.
The streamparticles function sets the following properties:
Animate to 10 to run the animation 10 times.
ParticleAlignment to on to start all particle traces together.
MarkerEdgeColor to none to draw only the face of the circular marker. Animations usually run faster when marker edges are not drawn.
MarkerFaceColor to red.
Marker to o, which draws a circular marker. You can use other line markers as well.
iverts = interpstreamspeed(x,y,z,u,v,w,verts,0.05); set(gca,'drawmode','fast'); streamparticles(iverts,15,... 'Animate',10,... 'ParticleAlignment','on',... 'MarkerEdgeColor','none',... 'MarkerFaceColor','red',... 'Marker','o');