Trying to do things with jit.gl.text3d in Max 5.1.7, I notice two minor issues in the maxhelp patch and the Reference document:
1) In the "Classic OpenGL Commands" sub-patcher, the fourth input of the color (RGBA) attribute (alpha/transparency) is not functional. The solution: adding a "blend_enable $1" message fixes this — when blend_enable is activated, the alpha value is working.
2) In the Reference document – also in the online version: http://www.cycling74.com/docs/max5/refpages/jit-ref/jit.gl.text3d.html – it says that the message "font – fontname [symbol] size [int]" "Specifies the font and size in which to draw." That seems to be a mistake, the "size" attribute has no effect. According to other threads on this forum, the recommended way to change the font size is by using the "scale" attribute.