title: Plotly 3d Surface trace does not show zero values
body: <p>I'm constructing a 3d plot that solves for a z value (aka c2) when c2 = 2.111* c1 + 21.1111 *c3.  Looks good when I create the following (see code below), but if you hover, the plotly trace does not show the values when c1 or c3 are zero -- the points just don't show!  I'm unclear whether I'm messing up the underlying data, or if this is a plotly display issue that I can resolve with some additional parameters.</p>
  
  <p>Grateful for any tips.  The code below should be sufficient to show the difficulty I'm encountering.</p>
  
  <pre><code># First create the values for the visualization
  myGrid &lt;- expand.grid(seq(0, 100, 1), seq(0, 100, 1))
  names(myGrid) &lt;- c("c1", "c3")
  myGrid$c2 &lt;- 2.111111*myGrid$c1 + 21.111111*myGrid$c3
  
  # go from long to wide, with c2 "inside" -- like a contingency table
  c2 &lt;- reshape(myGrid, direction = "wide", idvar = "c1", timevar = "c3")
  names(c2) &lt;- NA
  
  # make it a matrix.  Remove the row name col.
  c2 &lt;- as.matrix(c2[,-1])
  
  
  library(plotly)
  
  # Then create the textual labels
  txt &lt;- array(dim=dim(c2))
  for (x in 0:(dim(c2)[[2]]-1)) {
    for (y in 0:(dim(c2)[[1]] - 1)) {
      txt[1 + x*dim(c2)[[1]] + y] = paste('c1: $', x, '&lt;br /&gt;c3: $', y, '&lt;br /&gt;c2: $', c2[x+1,y+1])
    }
  }
  
  # create the plot
  p &lt;- plot_ly(z = c2,
               text = txt,
               hoverinfo = 'text') %&gt;% add_surface()
  p &lt;- layout(p, 
              title = "&lt;b&gt;Maximum Cost Combinations for Drug Testing&lt;/b&gt;&lt;br&gt;(Cost Combinations Falling on or Below Plane are Good Testing Candidates)",
              margin = list(
  
                pad = 4
              ),
              scene = list(xaxis = list(title = "c1"), 
                              yaxis = list(title = "c3"), 
                              zaxis = list(title = "c2"),
                              camera = list(eye = list(x = -1.7, y = 1.5, z = 1))
  )
  )
  
  p
  </code></pre>