I'm new to Blender and want to morph a sphere (or cube, cone, cylinder) into a torus.
Thanks for any help.
You can somehow fake the effect with shape keys.
It's just a matter of grouping vertex in the target position. The way about how to approach a similar problem could be various, and they really depends on the shapes.
Start by creating two shapkeys and enter edit mode to start changing the vertices position:
If we for example consider the morphing from a sphere, you could start by selecting the inner faces of the thorus and then scaling everything toward the center and then on the Z axis:
Invert the selection and start running alternatively the command "smooth vertex" and "to sphere". The purpose would be to better distribute the edge loops to mime a UV sphere topology (at least outside). Then scale the whole selection to match with the lower and upper vertex.
An approach using screw modifier and shape keys:
For instance, for the sphere: