在R中通过子集全脸顶点和指数数据绘制脸部表面网格的右半部分时遇到的错误。

Question

我有人脸的顶点和索引数据。此处. 我有一个 职位 一年前就根据这些数据绘制3D面部表面网格。现在，我想只绘制右半面和中面顶点，而忽略左侧顶点。根据我之前的绘图，我尝试了以下代码。

library(tidyverse)
library(readxl)
library(rgl)

vb <- read_excel("...\\vb.xlsx", sheet = "Sheet1", col_names = F)
it <- read_excel("...\\it.xlsx", sheet = "Sheet1", col_names = F)

# Extract vertices for the right side
lm_right_ind <- which(vb[,1] < 0)
vb_mat_right <- t(vb[lm_right_ind, ])
vb_mat_right <- rbind(vb_mat_right, 1)
rownames(vb_mat_right) <- c("xpts", "ypts", "zpts", "")
vertices1_right <- c(vb_mat_right)

# Extract `it` whose rows do not contain vertices on the left side
# Left-side vertices have vb[,1] greater than 0
lm_left_ind <- which(vb[,1] > 0)

leftContain <- NULL

for (i in 1: dim(it)[1]) {
   if (T %in% (it[i,] %in% lm_left_ind)) {
          leftContain[i] <- i
    } else {leftContain[i] <- NA}
}

leftContain <- leftContain[!is.na(leftContain)]
# Remove indices that involve left-side vertices
it_rightMid <- it[-leftContain,]

it_mat_right <- t(as.matrix(it_rightMid))
rownames(it_mat_right) <- NULL

indices_right <- c(it_mat_right)

# Plot
try1_right <- tmesh3d(vertices = vertices1_right, indices = indices_right, homogeneous = TRUE, 
             material = NULL, normals = NULL, texcoords = NULL)

# Use addNormals to smooth the plot. See my Stackoverflow question:
# https://stackoverflow.com/questions/53918849/smooth-3d-trangular-mesh-in-r
try12_right <- addNormals(try1_right)

shade3d(try12_right, col="#add9ec", specular = "#202020", alpha = 0.8)

我得到了一个错误的信息 try12_right:Error in v[, it[3, i]] : subscript out of bounds.

我的做法和我之前的情节一模一样，但是为什么这里出了问题？谢谢你。

Answer 1

下面是一个使用剪裁平面来留出网格对象的左侧的例子。

library(rgl)
open3d()
root <- currentSubscene3d()
newSubscene3d("inherit", "inherit", "inherit", parent = root) # Clipping limited to this subscene
shade3d(addNormals(subdivision3d(icosahedron3d(), 2)), col = "pink")
clipplanes3d(a = 1, b = 0, c = 0, d = 0)
useSubscene3d(root)
decorate3d()

子场景的处理限制了剪裁只限于阴影球体，而不是图片中的其他部分。

这样就会产生这样的输出。

如果那里没有其他东西，那就更简单了。 If there's nothing else there, it's simpler:

library(rgl)
open3d()
shade3d(addNormals(subdivision3d(icosahedron3d(), 2)), col = "pink")
clipplanes3d(a = 1, b = 0, c = 0, d = 0)

这就产生了