Remove z-fighting kludge

This was actually introducing z-fighting artefacts with the new shader and no added geometry.

cura/BuildVolume.py

@@ -181,7 +181,6 @@ class BuildVolume(SceneNode):
             self._grid_shader.setUniformValue("u_plateColor", Color(*theme.getColor("buildplate").getRgb()))
             self._grid_shader.setUniformValue("u_gridColor0", Color(*theme.getColor("buildplate_grid").getRgb()))
             self._grid_shader.setUniformValue("u_gridColor1", Color(*theme.getColor("buildplate_grid_minor").getRgb()))
-            self._grid_shader.setUniformValue("u_z_bias", 0.000001)
 
         renderer.queueNode(self, mode = RenderBatch.RenderMode.Lines)
         renderer.queueNode(self, mesh = self._origin_mesh)

resources/shaders/grid.shader

@@ -57,7 +57,6 @@ fragment41core =
     uniform lowp vec4 u_plateColor;
     uniform lowp vec4 u_gridColor0;
     uniform lowp vec4 u_gridColor1;
-    uniform lowp float u_z_bias; //Bias in the depth buffer for rendering this object (to make an object be rendered in front of or behind other objects).
 
     in lowp vec2 v_uvs;
     out vec4 frag_color;
@@ -77,14 +76,12 @@ fragment41core =
         float majorLine = min(majorGrid.x, majorGrid.y);
 
         frag_color = mix(minorGridColor, u_gridColor0, 1.0 - min(majorLine, 1.0));
-        gl_FragDepth = gl_FragCoord.z + u_z_bias;
     }
 
 [defaults]
 u_plateColor = [1.0, 1.0, 1.0, 1.0]
 u_gridColor0 = [0.96, 0.96, 0.96, 1.0]
 u_gridColor1 = [0.8, 0.8, 0.8, 1.0]
-u_z_bias = 0.0
 
 [bindings]
 u_modelViewProjectionMatrix = model_view_projection_matrix