add 4d rotation ops and view matrix calculation

1 files changed, 33 insertions, 0 deletions

diff --git a/src/4dvecops/vectoroperations.cpp b/src/4dvecops/vectoroperations.cpp
index d41dad3..a54b758 100644
--- a/src/4dvecops/vectoroperations.cpp
+++ b/src/4dvecops/vectoroperations.cpp
@@ -27,4 +27,37 @@ glm::vec4 dot4(
         glm::vec4 u,
         glm::vec4 v) {
     return {u[0] * v[0], u[1] * v[1], u[2] * v[2], u[3] * v[3]};
+}
+
+glm::mat4 getViewMatrix4(
+        glm::vec4 fromPoint,
+        glm::vec4 toPoint,
+        glm::vec4 upVector,
+        glm::vec4 overVector) {
+
+    // calculate e3 basis vector, the transformation col of view matrix
+    if (glm::distance(fromPoint, toPoint) < 0.0001f) {
+        throw std::runtime_error("fromPoint and toPoint are the same");
+    }
+    glm::vec4 e3 = glm::normalize(fromPoint - toPoint);
+
+    // calculate e2 basis vector, from the combinatory cross of up and over with e3
+    glm::vec4 e2 = cross4(upVector, overVector, e3);
+    e2 = glm::normalize(e2);
+    if (glm::distance(e2, glm::vec4{0, 0, 0, 1}) < 0.0001f) {
+        throw std::runtime_error("invalid up vector");
+    }
+
+    // calculate e1 basis vector, from the cross of only the over vector
+    glm::vec4 e1 = cross4(overVector, e3, e2);
+    e1 = glm::normalize(e1);
+    if (glm::distance(e1, glm::vec4{0, 0, 0, 1}) < 0.0001f) {
+        throw std::runtime_error("invalid over vector");
+    }
+
+    // calculate e0 basis vector, the 4d orthogonal vector to the other 3 bases
+    glm::vec4 e0 = cross4(e3, e2, e1);
+    e0 = glm::normalize(e0);
+
+    return {e2, e1, e0, e3};
 }
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