Migrate to NanoGUI / Eigen for GUI and linear algebra.

Also introduce a GUI play/pause button.

vis/include/cgl/error.hpp

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <stdexcept>
+
+#include <nanogui/opengl.h>
+
+namespace cgl {
+    class GlError : public std::domain_error {
+    public:
+        explicit GlError(const std::string &arg) : domain_error(arg) {}
+
+        explicit GlError(const char *string) : domain_error(string) {}
+    };
+
+    class ShaderError : public GlError {
+    public:
+        explicit ShaderError(const std::string &arg) : GlError(arg) {}
+
+        explicit ShaderError(const char *string) : GlError(string) {}
+    };
+
+    class ProgramError : public GlError {
+    public:
+        explicit ProgramError(const std::string &arg) : GlError(arg) {}
+
+        explicit ProgramError(const char *string) : GlError(string) {}
+    };
+}