[GL] Fix issue with clearing textures with unsigned integer formats

Author: hyazinthh

RELEASE_NOTES.md

@@ -2,6 +2,7 @@
 - Implemented download / upload for PixImage as 3D slices
 - Improved support for non-2D framebuffer outputs
 - [GL] Create debug context when debug output is enabled
+- [GL] Fixed issue with clearing textures with unsigned integer formats
 
 ### 5.6.1
 - [GeometryPool] culling shader workaround (FShade write bug)

src/Aardvark.Rendering.GL/Runtime/RenderTasks.fs

@@ -207,7 +207,10 @@ module RenderTasks =
                         match values.[att.Name] with
                         | Some c ->
                             if att.Format.IsIntegerFormat then
-                                GL.ClearBuffer(ClearBuffer.Color, i, c.Integer.ToArray())
+                                if att.Format.IsSigned then
+                                    GL.ClearBuffer(ClearBuffer.Color, i, c.Integer.ToArray())
+                                else
+                                    GL.ClearBuffer(ClearBuffer.Color, i, c.Integer.ToV4ui().ToArray())
                             else
                                 GL.ClearBuffer(ClearBuffer.Color, i, c.Float.ToArray())
                             GL.Check "could not clear buffer"