[Mesa-dev] [PATCH v2] mesa: rotation of 0-vector

[Sergii Romantsov]

Specification doesn't define behaviour for rotation of 0-vector.
Windows and Nvidia drivers have a workaround for that.
For compatibility proposed that for 0-vector a rotation will be
done around x-axis.

-v2: logic moved to _math_matrix_rotate

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100960
Signed-off-by: Sergii Romantsov <sergii.romantsov at globallogic.com>
---
 src/mesa/math/m_matrix.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/src/mesa/math/m_matrix.c b/src/mesa/math/m_matrix.c
index 57a4953..2b3adb3 100644
--- a/src/mesa/math/m_matrix.c
+++ b/src/mesa/math/m_matrix.c
@@ -824,6 +824,25 @@ _math_matrix_rotate( GLmatrix *mat,
                M(1,0) = s;
             }
          }
+         else {
+            /* https://bugs.freedesktop.org/show_bug.cgi?id=100960
+             * https://github.com/KhronosGroup/OpenGL-API/issues/41
+             * So that is kind of workaround for empty-vectors to have
+             * compatibility with Windows and Nvidia drivers.
+             */
+            optimized = GL_TRUE;
+            /* rotate only around x-axis */
+            M(1,1) = c;
+            M(2,2) = c;
+            if (x < 0.0F) {
+               M(1,2) = s;
+               M(2,1) = -s;
+            }
+            else {
+               M(1,2) = -s;
+               M(2,1) = s;
+            }
+         }
       }
       else if (z == 0.0F) {
          optimized = GL_TRUE;
-- 
2.7.4