Add image4 to README

README.md

@@ -9,7 +9,8 @@ Four-Space Visualization of 4D Objects
 This repository contains my 1991 thesis (converted to HTML from the original nroff sources), as well
 as the original code for my 4D wireframe viewer and my 4D raytracer.
 
-The thesis is now a single all-inclusive HTML file: [_Four-Space Visualization of 4D Objects_][].
+The thesis is now a single all-inclusive HTML file:
+[_Four-Space Visualization of 4D Objects_][thesis].
 
 See the [`thesis/`][] directory for my thesis source files and associated material.
 
@@ -33,10 +34,18 @@ and writes to standard output, so should be able to run on most computers. The o
 image that can be displayed with a variety of methods. See [`ray4-c/craig/`][craig] for some tools.
 
 
+Image4
+-------
+The [`image4`][] tool is a utility to query and display the 3D image cube generated by `ray4`. It's
+an entirely new tool in development. The plan is to have this tool generate PPM images from the 3D
+image cube.
+
+
 GitHub Notes
 -------------
 You can send any questions to me at [[email protected]](mailto:[email protected]). Also, now that
-GitHub has a discussions feature, feel free to start a conversation in [the discussions section][].
+GitHub has a discussions feature, feel free to start a conversation in
+[the discussions section][discussions].
 
 
 Other 4D Work
@@ -49,10 +58,11 @@ visualization work of their own. Here are links to other work I've seen.
 
 
 
-[_Four-Space Visualization of 4D Objects_]: https://hollasch.github.io/ray4/Four-Space_Visualization_of_4D_Objects.html
-[the discussions section]:                  https://github.com/hollasch/ray4/discussions/
-[`ray4-c`]:                                 ray4-c/README.md
-[`ray4`]:                                   ray4/README.md
-[craig]:                                    ray4-c/craig/README.md
-[`wire4`]:                                  wire4/README.md
-[`thesis/`]:                                thesis/README.md
+[`image4`]:    image4/README.md
+[`ray4-c`]:    ray4-c/README.md
+[`ray4`]:      ray4/README.md
+[`thesis/`]:   thesis/README.md
+[`wire4`]:     wire4/README.md
+[craig]:       ray4-c/craig/README.md
+[discussions]: https://github.com/hollasch/ray4/discussions/
+[thesis]:      https://hollasch.github.io/ray4/Four-Space_Visualization_of_4D_Objects.html