Merge pull request #410 from dmurdoch/alphatexture

Use luminance to retrieve value for `textype="alpha"`

NEWS.md

@@ -1,4 +1,4 @@
-# rgl 1.2.13
+# rgl 1.2.14
 
 ## Major changes
 
@@ -28,6 +28,7 @@ run in a Shiny session.
 * Fixed issue with `warning()` call reported by CRAN.
 * Smooth shapes were not rendered correctly by `rglwidget()`.
  This was especially noticeable for spheres with `fov = 0`, but was present in other cases as well (issue #401).
+* `textype = "alpha"` was not rendered correctly by `rglwidget()` (issue #408).
 
 # rgl 1.2.1
 

inst/htmlwidgets/lib/rglClass/shaders/rgl_fragment.glsl

@@ -203,15 +203,17 @@ void main(void) {
 #endif //TEXTURE_rgba
 
 #ifdef TEXTURE_alpha
+ float luminance = dot(vec3(1.,1.,1.),textureColor.rgb)/3.;
+
 #if defined(TEXMODE_replace) || defined(TEXMODE_decal)
- textureColor = vec4(lighteffect.rgb, textureColor.a);
+ textureColor = vec4(lighteffect.rgb, luminance);
 #endif 
 
 #if defined(TEXMODE_modulate) || defined(TEXMODE_blend) || defined(TEXMODE_add)
- textureColor = vec4(lighteffect.rgb, lighteffect.a*textureColor.a);
+ textureColor = vec4(lighteffect.rgb, lighteffect.a*luminance);
 #endif
 
-#endif
+#endif // TEXTURE_alpha
 
 // The TEXTURE_luminance values are not from that reference 
 #ifdef TEXTURE_luminance

man/material.Rd

@@ -113,6 +113,13 @@ of objects in an \pkg{rgl} scene.
  \item{"rgb"}{color}
  \item{"rgba"}{color and alpha texture}
  }
+ Note that support for these modes is slightly different
+in the display within R versus the WebGL display using
+\code{rglwidget()}. In particular, in WebGL 
+\code{textype = "alpha"} will always take the alpha value from
+the luminance (i.e. the average of the R, G and B channels) 
+of the texture, whereas the R display bases
+the choice on the internal format of the texture file.
  }
  \item{texmode}{
  specifies how the texture interacts with the existing