# Unexpected behaviour of RegionFunction in 3D Plots [duplicate]

This question is an exact duplicate of:

This is a continuation of a similar problem I had posted earlier.

I am trying to plot a function defined in a specific parameter space using the RegionFunction option in Plot3D.

So, this is how I define the region where I want to plot my function

Vld[l_, c_] = If[0 < Q3A < 1 && 1 > A > 0 && 1 > B > 0, True,  False]


Then, I do

A = 1/2; B = 1/2; H = 2/10; G = 1/2;


Followed by

Plot1 =
Plot3D[PU, {L, 00, 1}, {c, 0.0, 1},
AxesLabel -> {"L", "c", "PlatformUtil"},
RegionFunction -> Function[{x, y}, Vld[x, y]],
PlotRange -> All,
ImageSize -> Large]


Where PU is also a function of the parameters and Q3A.

When I try Reduce[Vld[L, c] && PU > 2]

I get False

When I look at the plot, I should not see any value above 1, but I see a few spikes in the corner.

Am I doing something wrong in the way I am using the region function?

## marked as duplicate by m_goldberg plotting StackExchange.ready(function() { if (StackExchange.options.isMobile) return; $('.dupe-hammer-message-hover:not(.hover-bound)').each(function() { var$hover = $(this).addClass('hover-bound'),$msg = $hover.siblings('.dupe-hammer-message');$hover.hover( function() { $hover.showInfoMessage('', { messageElement:$msg.clone().show(), transient: false, position: { my: 'bottom left', at: 'top center', offsetTop: -7 }, dismissable: false, relativeToBody: true }); }, function() { StackExchange.helpers.removeMessages(); } ); }); }); Sep 5 '18 at 23:36

This question was marked as an exact duplicate of an existing question.

• This question is not sufficiently different from your previous question to merit being a separate post. Please update your previous question to include the variation you introduce here. – m_goldberg Sep 5 '18 at 23:38
• Thank you m_goldberg. I have updated my old question. – SreeVathsan Sep 6 '18 at 3:34