This example plots the velocity vector cones for the
The graph produced employs a number of visualization techniques:
An isosurface is used to provide visual context for the cone plots and to provide means to select a specific data value for a set of cones.
Lighting enables the shape of the isosurface to be clearly visible.
The use of perspective projection, camera positioning, and view angle adjustments composes the final view.
Displaying an isosurface within the rectangular space of the data provides a visual context for the cone plot. Creating the isosurface requires a number of steps:
Calculate the magnitude of the vector field, which represents the speed of the wind.
patch to draw an isosurface
illustrating where in the rectangular space the wind speed is equal to a
particular value. Regions inside the isosurface have higher wind speeds,
regions outside the isosurface have lower wind speeds.
isonormals to compute
vertex normals of the isosurface from the volume data rather than calculate
the normals from the triangles used to render the isosurface. These normals
generally produce more accurate results.
Set visual properties of the isosurface, making it red and without drawing
load wind wind_speed = sqrt(u.^2 + v.^2 + w.^2); hiso = patch(isosurface(x,y,z,wind_speed,40)); isonormals(x,y,z,wind_speed,hiso) hiso.FaceColor = 'red'; hiso.EdgeColor = 'none';
Isocaps are similar to slice planes in that they show a cross section of the
volume. They are designed to be the end caps of isosurfaces. Using interpolated face
color on an isocap causes a mapping of data value to color in the current colormap.
To create isocaps for the isosurface, define them at the same isovalue (
hcap = patch(isocaps(x,y,z,wind_speed,40),... 'FaceColor','interp',... 'EdgeColor','none'); colormap hsv
daspect to set the data
aspect ratio of the axes before calling
function can determine the proper size of the cones.
Determine the points at which to place cones by calculating another
isosurface that has a smaller isovalue (so the cones are displayed outside
the first isosurface) and use
reducepatch to reduce the
number of faces and vertices (so there are not too many cones on the
Draw the cones and set the face color to
blue and the
edge color to
daspect([1 1 1]); [f,verts] = reducepatch(isosurface(x,y,z,wind_speed,30),0.07); h1 = coneplot(x,y,z,u,v,w,verts(:,1),verts(:,2),verts(:,3),3); h1.FaceColor = 'blue'; h1.EdgeColor = 'none';
Draw a second set of cones and set the face color to green and the edge color to none.
xrange = linspace(min(x(:)),max(x(:)),10); yrange = linspace(min(y(:)),max(y(:)),10); zrange = 3:4:15; [cx,cy,cz] = meshgrid(xrange,yrange,zrange); h2 = coneplot(x,y,z,u,v,w,cx,cy,cz,2); h2.FaceColor = 'green'; h2.EdgeColor = 'none';
axis tight set(gca,'BoxStyle','full','Box','on') camproj perspective camzoom(1.25) view(65,45)
Add a light source and use Gouraud lighting for the smoothest lighting of the
isosurface. Increase the strength of the background lighting on the isocaps to make
them brighter (
camlight(-45,45) hcap.AmbientStrength = 0.6; lighting gouraud