# CountourPlot3D problem when intersecting semiplanes

I have the following code:

RegionPlot3D[x + y + z <= 3 && x + z <= 1, {x, 0, 3}, {y, 0, 3}, {z, 0, 2} , BoxRatios -> Automatic, AxesLabel -> Automatic]


To get the following picture seen from below:

As you can see, 3 diferent lines appear when I'm just intersecting 2 semiplanes.

I have tried with different mesh options but i couldn't find the key to this problem.

• add the option PlotPoints -> 200? – kglr Nov 3 '20 at 12:21
• or the options PlotPoints -> 60, and MaxRecursion -> 7? – kglr Nov 3 '20 at 12:22
• @klgr Using PlotPoints -> 100 does the trick, but it takes a little bit longer. But thanks I didnt't know that option. – Alejandro Mahillo Nov 3 '20 at 14:47

For plane, we can decreasing the MaxCellMeasure instead of increasing it.
reg = ImplicitRegion[