Shadows for MATLAB®

Algorithms for computing and drawing shadows that are cast by a triangulation. The computed shadows work well when they are drawn on the "walls" of an axes. Several utilities are provided depending on the shadow needed.

A triangulation holds the geometry of the thing that will be casting the shadow. The function tri2shadow will compute a shadow projection against an Axes wall for a given light location.

The utilities triMeshShadow and triMeshShadow3 will accept a triangulation and light location, and draw the triangulation, the shadow, and the light in an axes. triMeshShadow will only draw on the floor of the axes. triMeshShadow3 will draw shadows on all visible walls of the Axes.

In addition, this repo contains examples on building triangulations that cast interesting shadows (see examples.)

Examples

Draw a shadow using triMeshShadow.

sz=50;
t=linspace(0,2,sz)';
x=cospi(t);
y=sinpi(t);
z=cospi(t*4)/3;
tri = triangulation([ 1:sz; 2:sz 1; [2:sz 1]+sz; (1:sz)+sz ]',...
                    [x y z+3; x*2 y*2 -z+3]);
triMeshShadow(tri);

See Examples_ProjectingShadows.mlx for details:

Compute a projection of a desired shadow onto a sphere using ps2stereographicsphere.

[tri, lz] = ps2stereographicsphere(shapegrid(5,4,'Radius',.75));
triMeshShadow(tri, [0 0 lz], 'Attenuation',8);

See Examples_StereographicProjections.mlx for details.

Compute shadow projections on all 3 walls of the axes, and animate the light through the scene.

[tri, lz] = ps2stereographicsphere(hexgrid);
H=triMeshShadow3(tri, [0 0 lz], 'Attenuation',8);
drawnow
H.updateShadows([0 0 lz-.5]);

See Examples_animation.m for details.

Create STL files of some tiled polygon shapes stereographicly projected onto a sphere.

makeShadowModels;

MathWorks® Products (https://www.mathworks.com)

• Partial Differential Equasion Toolbox™ will be used for meshing polyshapes if it is installed.

License

The license is available in the License.txt file in this GitHub repository.

Copyright 2024 The MathWorks, Inc.