add cglm as 3rd-party library

1 files changed, 61 insertions, 0 deletions

diff --git a/libs/cglm/docs/source/opengl.rst b/libs/cglm/docs/source/opengl.rst
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+How to send vector or matrix to OpenGL like API
+==================================================
+
+*cglm*'s vector and matrix types are arrays. So you can send them directly to a
+function which accepts pointer. But you may got warnings for matrix because it is
+two dimensional array.
+
+Passing / Uniforming Matrix to OpenGL:
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+**glUniformMatrix4fv** accepts float pointer, you can pass matrix to that parameter
+and it should work but with warnings. "You can pass" doesn't mean that you must pass like that.
+
+**Correct options:**
+
+Correct doesn't mean correct way to use OpenGL it is just shows correct way to pass cglm type to it.
+
+1. Pass first column
+---------------------
+
+The goal is that pass address of matrix, first element of matrix is also address of matrix,
+because it is array of vectors and vector is array of floats.
+
+.. code-block:: c
+
+   mat4 matrix;
+   /* ... */
+   glUniformMatrix4fv(location, 1, GL_FALSE, matrix[0]);
+
+array of matrices:
+
+.. code-block:: c
+
+   mat4 matrix;
+   /* ... */
+   glUniformMatrix4fv(location, count, GL_FALSE, matrix[0][0]);
+
+1. Cast matrix to pointer
+--------------------------
+
+.. code-block:: c
+
+   mat4 matrix;
+   /* ... */
+   glUniformMatrix4fv(location, count, GL_FALSE, (float *)matrix);
+
+in this way, passing aray of matrices is same
+
+Passing / Uniforming Vectors to OpenGL:
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+You don't need to do extra thing when passing cglm vectors to OpengL or other APIs.
+Because a function like **glUniform4fv** accepts vector as pointer. cglm's vectors
+are array of floats. So you can pass it directly ot those functions:
+
+.. code-block:: c
+
+   vec4 vec;
+   /* ... */
+   glUniform4fv(location, 1, vec);
+
+this show how to pass **vec4** others are same.