Adds a frame transformation example

examples/CMakeLists.txt

@@ -534,6 +534,9 @@ add_executable(maketicks maketicks.cpp)
 add_executable(coordarrows coordarrows.cpp)
 target_link_libraries(coordarrows OpenGL::GL glfw Freetype::Freetype)
 
+add_executable(frames frames.cpp)
+target_link_libraries(frames OpenGL::GL glfw Freetype::Freetype)
+
 add_executable(sph_to_cart sph_to_cart.cpp)
 target_link_libraries(sph_to_cart OpenGL::GL glfw Freetype::Freetype)
 

examples/frames.cpp

@@ -0,0 +1,81 @@
+/*
+ * Demonstrating coordinate frame transformations
+ */
+#include <iostream>
+#include <sm/vec>
+#include <sm/mat>
+#include <mplot/Visual.h>
+#include <mplot/CoordArrows.h> // This is the only VisualModel derived class not called SomethingVisual!
+
+int main()
+{
+    mplot::Visual v(1024, 768, "Slerping");
+    v.lightingEffects (true);
+
+    // A is the end location coordinate arrows (darker)
+    sm::vec<float> offset = {};
+    auto cavm = std::make_unique<mplot::CoordArrows<>> (offset);
+    v.bindmodel (cavm);
+    cavm->x_axis_col = mplot::colour::maroon;
+    cavm->y_axis_col = mplot::colour::darkgreen;
+    cavm->z_axis_col = mplot::colour::midnightblue;
+    cavm->finalize();
+    auto cA = v.addVisualModel (cavm);
+
+    // B is the starting location coordinate arrows (lighter)
+    cavm = std::make_unique<mplot::CoordArrows<>> (offset);
+    v.bindmodel (cavm);
+    cavm->x_axis_col = mplot::colour::firebrick1;
+    cavm->y_axis_col = mplot::colour::palegreen3;
+    cavm->z_axis_col = mplot::colour::steelblue1;
+    cavm->finalize();
+    auto cB = v.addVisualModel (cavm);
+
+    cavm = std::make_unique<mplot::CoordArrows<>> (offset);
+    v.bindmodel (cavm);
+    cavm->finalize();
+    auto cC = v.addVisualModel (cavm);
+
+    // Define A's location as a viewmatrix. Apply a rotation (first) then a translation
+    sm::mat<float, 4> A;
+    A.translate (sm::vec<float>{0.2,0.4,0});
+    A.rotate (sm::vec<float>::uy(), sm::mathconst<float>::pi_over_4);
+
+    // The starting location.
+    sm::mat<float, 4> B;
+    B.translate (sm::vec<float>{1,1,1});
+    B.rotate (sm::vec<float>::uz(), sm::mathconst<float>::pi_over_2);
+
+    // From A and B find the pure translation between the two
+    sm::vec<float> delta_x = A.translation() - B.translation();
+
+    // Compute the pre-translation rotations
+    sm::mat<float, 4> A0 = A;
+    A0.translate (-A.translation());
+    sm::mat<float, 4> B0 = B;
+    B0.translate (-B.translation());
+    sm::quaternion<float> rA = A0.rotation();
+    sm::quaternion<float> rB = B0.rotation();
+
+    // Set the viewmatrix for both A and B coordinate arrows (these will stay fixed)
+    cA->setViewMatrix (A);
+    cB->setViewMatrix (B);
+
+    int count = 0;
+    while (!v.readyToFinish()) {
+
+        v.render();
+        v.wait (0.018);
+
+        float prop = static_cast<float>(count++ % 100) / 100.0f;
+
+        // Compute the intermediate translation and rotation, C and apply this to the cC coordinate arrows
+        sm::mat<float, 4> C;
+        // C is a rotation of the intermediate rotation between rA and rB, then a translation to B +
+        // the intermediate delta_x:
+        C.translate (B.translation() + prop * delta_x);
+        C.rotate (rB.slerp (rA, prop));
+
+        cC->setViewMatrix (C);
+    }
+}