R Under development (unstable) (2023-11-26 r85638 ucrt) -- "Unsuffered Consequences"
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> library(rgl)
> open3d()
wgl 
  1 
> set.seed(3)
>  x <- cube3d(col="white", texture = system.file("textures/rgl2.png",
+                                                 package = "rgl"),
+              texcoords = matrix(runif(16), ncol=2))
> id <- shade3d(x)
> # rglwidget()
> 
> 
> 
> vShader <- "
+ /* ****** quads object 13 vertex shader ****** */
+   #ifdef GL_ES
+   #ifdef GL_FRAGMENT_PRECISION_HIGH
+   precision highp float;
+ #else
+ precision mediump float;
+ #endif
+ #endif
+ attribute vec3 aPos;
+ attribute vec4 aCol;
+ uniform mat4 mvMatrix;
+ uniform mat4 prMatrix;
+ varying vec4 vCol;
+ varying vec4 vPosition;
+ attribute vec3 aNorm;
+ uniform mat4 normMatrix;
+ varying vec4 vNormal;
+ attribute vec2 aTexcoord;
+ varying vec2 vTexcoord;
+ void main(void) {
+   vPosition = mvMatrix * vec4(aPos, 1.);
+   gl_Position = prMatrix * vPosition;
+   vCol = aCol;
+   vNormal = normMatrix * vec4(-aNorm, dot(aNorm, aPos));
+   vNormal = vec4(normalize(vNormal.xyz/vNormal.w), 1);
+   vTexcoord = aTexcoord;
+ }
+ "
> fShader <- "
+ /* ****** quads object 13 fragment shader ****** */
+   #ifdef GL_ES
+   #ifdef GL_FRAGMENT_PRECISION_HIGH
+   precision highp float;
+ #else
+ precision mediump float;
+ #endif
+ #endif
+ varying vec4 vCol; // carries alpha
+ varying vec4 vPosition;
+ varying vec2 vTexcoord;
+ uniform sampler2D uSampler;
+ uniform sampler2D userSampler;
+ uniform int uFogMode;
+ uniform vec3 uFogColor;
+ uniform vec4 uFogParms;
+ varying vec4 vNormal;
+ uniform mat4 mvMatrix;
+ uniform vec3 emission;
+ uniform float shininess;
+ uniform vec3 ambient0;
+ uniform vec3 specular0; // light*material
+ uniform vec3 diffuse0;
+ uniform vec3 lightDir0;
+ uniform bool viewpoint0;
+ uniform bool finite0;
+ void main(void) {
+   vec4 fragColor;
+   vec3 n = normalize(vNormal.xyz + texture2D(userSampler, vTexcoord).rgb);
+   vec3 eye = normalize(-vPosition.xyz/vPosition.w);
+   vec3 lightdir;
+   vec4 colDiff;
+   vec3 halfVec;
+   vec4 lighteffect = vec4(emission, 0.);
+   vec3 col;
+   float nDotL;
+   n = -faceforward(n, n, eye);
+   colDiff = vec4(vCol.rgb * diffuse0, vCol.a);
+   lightdir = lightDir0;
+   if (!viewpoint0)
+     lightdir = (mvMatrix * vec4(lightdir, 1.)).xyz;
+   if (!finite0) {
+     halfVec = normalize(lightdir + eye);
+   } else {
+     lightdir = normalize(lightdir - vPosition.xyz/vPosition.w);
+     halfVec = normalize(lightdir + eye);
+   }
+   col = ambient0;
+   nDotL = dot(n, lightdir);
+   col = col + max(nDotL, 0.) * colDiff.rgb;
+   col = col + pow(max(dot(halfVec, n), 0.), shininess) * specular0;
+   lighteffect = lighteffect + vec4(col, colDiff.a);
+   vec4 textureColor = lighteffect*vec4(1.,1.,1.,1.);
+   fragColor = textureColor;
+   float fogF;
+   if (uFogMode > 0) {
+     fogF = (uFogParms.y - vPosition.z/vPosition.w)/(uFogParms.y - uFogParms.x);
+     if (uFogMode > 1)
+       fogF = mix(uFogParms.w, 1.0, fogF);
+     fogF = fogF*uFogParms.z;
+     if (uFogMode == 2)
+       fogF = 1.0 - exp(-fogF);
+     else if (uFogMode == 3)
+       fogF = 1.0 - exp(-fogF*fogF);
+     fogF = clamp(fogF, 0.0, 1.0);
+     gl_FragColor = vec4(mix(fragColor.rgb, uFogColor, fogF), fragColor.a);
+   } else gl_FragColor = fragColor;
+ }
+ "
> 
> s <- setUserShaders(id, vertexShader = vShader,
+                         fragmentShader = fShader,
+                textures = c(userSampler = system.file("textures/rgl2.png",
+                                       package = "rgl"),
+                             unusedSampler = system.file("textures/rgl2.png",
+                                                         package = "rgl")),
+                uniforms = list(unusedUniform = 3),
+                attributes = list(unusedAttribute = 1:10))
> rglwidget(s)
> 
> proc.time()
   user  system elapsed 
   0.56    0.10    0.65