Apply texture to a Shade3d object such as Cube3d

[duckt14]

Hi, I'm trying to apply a texture image to a Cube3d, but in the renderer window the cube hasn't texture and it appears black on all faces. I'm using these two different ways:

texture <- here("3D/texture/txt.png") shade3d(cube3d(), texture = texture) or shade3d(cube3d(texture = texture))

But it doesn't work. With the Sphere3d it works well. Is there any solution? Very thanks, Enrico

• rgl Version: 1.0.1
• R Version: 4.2.2
• Platform: Windows 10

[dmurdoch]

On 25/01/2023 10:06 a.m., duckt14 wrote:

Hi, I'm trying to apply a texture image to a Cube3d, but in the renderer window the cube hasn't texture and it appears black on all faces. I'm using these two different ways:

|texture <- here("3D/texture/txt.png")| |shade3d(cube3d(), texture = texture)| or |shade3d(cube3d(texture = texture))|

But it doesn't work. With the Sphere3d it works well. Is there any solution?

You need to set col = "white" as well. By default the color of the cube is black, and textures modify it multiplicatively.

It might make sense to change this, but it's been like that for a very long time, so it would cause some disruption.

Duncan Murdoch

[duckt14]

Okay, I've tested using this line shade3d(cube3d(texture = texture, col = "white")) and I attach you the results. With sphere works correctly and with the cube I've obtained only a colored mesh. Perhaps, I need to add some settings; I've tried follow the reference about material but I'm not able to showing the texture on cube. :-/

This is the texture:

These are the results:

[dmurdoch]

It looks as though you have specified texture coordinates on the sphere but not on the cube. You can see what the space coordinates of the cube are by running cube3d()$vb. Those are homogeneous coordinates, one vertex per column. You need to choose where each vertex should show up in the texture. Here's one example:

cube <- cube3d(texcoords = cbind(vb[1,] + vb[2,] + vb[3,],
                                 vb[1,] - vb[2,] + 2*vb[3,]), 
               col = "white",
               texture = system.file("textures/rgl2.png", package="rgl"))
shade3d(cube)

This gives this image:

One problem you'll have if you try to put a texture on a cube is that texture coordinates map to vertices, which means you get the same texture coordinate at the vertex on all three faces that meet there; it's not like drawing a PNG file on each face. To do that, you would need to plot 6 quads (with a total of 24 vertices and 24 texture coordinate pairs). This does that:

id <- shade3d(cube, meshColor = "faces")
vertices <- rgl.attrib(id, "vertices")
open3d()
quads3d(vertices, col = "white", 
        texcoords = cbind(rep(c(0, 0, 1, 1), 6), 
                          rep(c(0, 1, 1, 0), 6)), 
        texture = system.file("textures/rgl2.png", package="rgl"))

[duckt14]

It works!! Really many thanks Duncan for the help and for your work. 🙏❣️

[duckt14]

@dmurdoch is there a solution to apply different texture on each cube faces?

[dmurdoch]

On 26/01/2023 5:00 a.m., duckt14 wrote:

@dmurdoch https://github.com/dmurdoch is there a solution to apply different texture on each cube faces?

You can only have one texture per object, so there are two possible solutions:

• plot each face as a separate object using 6 calls to quads3d
• join the textures together into a single PNG file, and use the texcoords settings to choose different parts of the image to display, e.g. one face goes from 0 to 1/3 in s, 0 to 1/2 in t, the next one goes from 1/3 to 2/3 in s, 0 to 1/2 in t, etc.

Duncan Murdoch