graph a function restricted in R - r

Question

I'd want to plot a function: f(x,y)=x^2-2*y, with a constraint: x+y=1
in my graph functions overlap , well not seen the restricted function f(x,y). Would appreciate better if x+y-1=0 were transparent.
Mi code in R:
x <- seq(-5, 5, length= 10)
y <- x
fun1<-function(x,y){x^2-2*y}
m <- outer(x, y, fun1)
m[is.na(m)] <- 1
persp(x, y, m, theta = 30, phi = 30,
expand = 0.5, col = "royalblue", ltheta = 120,
shade = 0.75, ticktype = "detailed")
par(new=TRUE)
fun1<-function(x,y){x+y-1}
m <- outer(x, y, fun2)
m[is.na(m)] <- 1
persp(x, y, m, theta = 30, phi = 30,
expand = 0.5, col = "red", ltheta = 120,
shade = 0.75, ticktype = "detailed")

Answer 1

Some overplotting might help. First plot as suggested in comments above. Then de-select the segments where the constraint is violated by assigning NA, i.e. no plotting and overplot with a heavier color. ( I found that unless I froze the z-limits that they "shifted" at the last step. You may need to suppress the z-axis labels, since they are still overlaying each other.)
png(); x <- seq(-5, 5, length= 10)
y <- x
fun1<-function(x,y){x^2-2*y}
m1 <- outer(x, y, fun1)
m1[is.na(m)] <- 1
persp(x, y, m1, theta = 30, phi = 30,
expand = 0.5, col = "#4169E155", ltheta = 120,
shade = 0.75, ticktype = "detailed",zlim=c(-15,35))
par(new=TRUE)
fun2<-function(x,y){x+y-1}
m2 <- outer(x, y, fun2)
m2[is.na(m)] <- 1
persp(x, y, m2, theta = 30, phi = 30,
expand = 0.5, col = adjustcolor("red", alpha.f=0.5), ltheta = 120,
shade = 0.75, ticktype = "detailed",zlim=c(-15,35))
par(new=TRUE)
fun3<-function(x,y){x^2-2*y}
m3 <- outer(x, y, fun3)
m3[ m3 < m2 ] <- NA # <--- logical indexing; this is the key step
persp(x, y, m3, theta = 30, phi = 30,
expand = 0.5, col = "#4169E1", ltheta = 120, # solid-blue
shade = 0.75, ticktype = "detailed",zlim=c(-15,35));dev.off()