port invert and transformMat4 from gl-matrix

1 files changed, 47 insertions, 0 deletions

diff --git a/src/mbgl/util/mat4.cpp b/src/mbgl/util/mat4.cpp
index 59137ded37..123c8464fd 100644
--- a/src/mbgl/util/mat4.cpp
+++ b/src/mbgl/util/mat4.cpp
@@ -45,6 +45,53 @@ void matrix::identity(mat4& out) {
     out[15] = 1.0f;
 }
 
+bool matrix::invert(mat4& out, mat4& a) {
+    float a00 = a[0], a01 = a[1], a02 = a[2], a03 = a[3],
+          a10 = a[4], a11 = a[5], a12 = a[6], a13 = a[7],
+          a20 = a[8], a21 = a[9], a22 = a[10], a23 = a[11],
+          a30 = a[12], a31 = a[13], a32 = a[14], a33 = a[15],
+
+          b00 = a00 * a11 - a01 * a10,
+          b01 = a00 * a12 - a02 * a10,
+          b02 = a00 * a13 - a03 * a10,
+          b03 = a01 * a12 - a02 * a11,
+          b04 = a01 * a13 - a03 * a11,
+          b05 = a02 * a13 - a03 * a12,
+          b06 = a20 * a31 - a21 * a30,
+          b07 = a20 * a32 - a22 * a30,
+          b08 = a20 * a33 - a23 * a30,
+          b09 = a21 * a32 - a22 * a31,
+          b10 = a21 * a33 - a23 * a31,
+          b11 = a22 * a33 - a23 * a32,
+
+          // Calculate the determinant
+          det = b00 * b11 - b01 * b10 + b02 * b09 + b03 * b08 - b04 * b07 + b05 * b06;
+
+    if (!det) {
+        return true;
+    }
+    det = 1.0 / det;
+
+    out[0] = (a11 * b11 - a12 * b10 + a13 * b09) * det;
+    out[1] = (a02 * b10 - a01 * b11 - a03 * b09) * det;
+    out[2] = (a31 * b05 - a32 * b04 + a33 * b03) * det;
+    out[3] = (a22 * b04 - a21 * b05 - a23 * b03) * det;
+    out[4] = (a12 * b08 - a10 * b11 - a13 * b07) * det;
+    out[5] = (a00 * b11 - a02 * b08 + a03 * b07) * det;
+    out[6] = (a32 * b02 - a30 * b05 - a33 * b01) * det;
+    out[7] = (a20 * b05 - a22 * b02 + a23 * b01) * det;
+    out[8] = (a10 * b10 - a11 * b08 + a13 * b06) * det;
+    out[9] = (a01 * b08 - a00 * b10 - a03 * b06) * det;
+    out[10] = (a30 * b04 - a31 * b02 + a33 * b00) * det;
+    out[11] = (a21 * b02 - a20 * b04 - a23 * b00) * det;
+    out[12] = (a11 * b07 - a10 * b09 - a12 * b06) * det;
+    out[13] = (a00 * b09 - a01 * b07 + a02 * b06) * det;
+    out[14] = (a31 * b01 - a30 * b03 - a32 * b00) * det;
+    out[15] = (a20 * b03 - a21 * b01 + a22 * b00) * det;
+
+    return false;
+}
+
 void matrix::ortho(mat4& out, double left, double right, double bottom, double top, double near, double far) {
     double lr = 1.0f / (left - right),
           bt = 1.0f / (bottom - top),