Set user-defined shaders for RGL objects, or get shaders.

setUserShaders sets user-defined shaders (programs written in GLSL) for customized display of RGL objects. Currently only supported in WebGL displays, as the regular displays do not support GLSL. getShaders gets the user defined shader, or if it is not present, the automatically generated one.

setUserShaders(ids, vertexShader = NULL, fragmentShader = NULL, 
               attributes = NULL, uniforms = NULL, textures = NULL,
               scene = scene3d(minimal), minimal = TRUE)

getShaders(id, scene = scene3d(minimal), minimal = TRUE)

Arguments

ids, id

Which objects should receive the shaders, or which object should be queried?

vertexShader, fragmentShader

The vertex and fragment shader source code. If NULL, the automatically generated shader will be used instead.

attributes

A named list of “attributes” to attach to each vertex.

uniforms

A named list of “uniforms”.

textures

A named list of textures.

scene

A scene3d object to work with.

minimal

See scene3d.

Details

Modern versions of OpenGL work with “shaders”, programs written to run on the graphics processor. The vertex shader does the calculations to move vertices and set their intrinsic colours. The fragment shader computes how each pixel in the display will be shown, taking into account lighting, material properties, etc. (More precisely, it does the computation for each “fragment”; a fragment is a pixel within an object to display. There may be many objects at a particular location, and each will result in a fragment calculation unless culled by z-buffering or being discarded in some other way.)

Normally the WebGL Javascript code uses the default shaders stored in system.file("htmlwidgets/lib/rglClass/shaders", package = "rgl"). This function allows them to be written by hand, for testing new features, hand optimization, etc. The defines used by the default shaders will also be prepended to user shaders, which can use them for customization on an object-by-object basis.

The names used for the attributes, uniforms and textures should match names in the shaders for corresponding variables. (The texture names should be names of uniform sampler2D variables.)

Note

The getShaders function requires the V8 package to extract auto-generated shaders, since the defines are generated by Javascript code.

Value

A modified version of the scene.

Author

Duncan Murdoch

See also

rglwidget for display of the scene in WebGL.

Examples

open3d()
id <- shade3d(octahedron3d(), col = "red")

# For each triangle, set weights on the 3 vertices.
# This will be replicated to the appropriate size in Javascript.
wts <- diag(3)

# This leaves out the centres of each face
vs <- "
  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 vec3 vNormal;
  attribute vec3 wts;
  varying vec3 vwts;
  void main(void) {
    vPosition = mvMatrix * vec4(aPos, 1.);
    gl_Position = prMatrix * vPosition;
    vCol = aCol;
    vNormal = normalize((normMatrix * vec4(aNorm, 1.)).xyz);
    vwts = wts;
  }
"  
fs <- "
  #ifdef GL_ES
  precision highp float;
  #endif
  varying vec4 vCol; // carries alpha
  varying vec4 vPosition;
  varying vec3 vNormal;
  uniform mat4 mvMatrix;
  uniform vec3 emission;
  uniform float shininess;
  uniform vec3 ambient[NLIGHTS];
  uniform vec3 specular[NLIGHTS]; // light*material
  uniform vec3 diffuse[NLIGHTS];
  uniform vec3 lightDir[NLIGHTS];
  uniform bool viewpoint[NLIGHTS];
  uniform bool finite[NLIGHTS];
  varying vec3 vwts;
  uniform vec2 wtrange;
  void main(void) {
    float minwt = min(vwts.x, min(vwts.y, vwts.z));
    if (minwt < wtrange.x || minwt > wtrange.y) discard;
    vec3 eye = normalize(-vPosition.xyz);
    vec3 lightdir;
    vec4 colDiff;
    vec3 halfVec;
    vec4 lighteffect = vec4(emission, 0.);
    vec3 col;
    float nDotL;
    vec3 n = normalize(vNormal);
    n = -faceforward(n, n, eye);
    colDiff = vec4(vCol.rgb * diffuse[0], vCol.a);
    lightdir = lightDir[0];
    if (!viewpoint[0])
      lightdir = (mvMatrix * vec4(lightdir, 1.)).xyz;
    if (!finite[0]) {
      halfVec = normalize(lightdir + eye);
    } else {
      lightdir = normalize(lightdir - vPosition.xyz);
      halfVec = normalize(lightdir + eye);
    }
    col = ambient[0];
    nDotL = dot(n, lightdir);
    col = col + max(nDotL, 0.) * colDiff.rgb;
    col = col + pow(max(dot(halfVec, n), 0.), shininess) * specular[0];
    lighteffect = lighteffect + vec4(col, colDiff.a);
    gl_FragColor = lighteffect;
  }
"
x <- setUserShaders(id, vs, fs, attributes = list(wts=wts),
                    uniforms = list(wtrange = c(-0.01, 0.15)))
if (interactive() || in_pkgdown_example())
  rglwidget(x)