So the WebGL spec is mostly just a way to understand what the differences from OpenGL-ES-2 are. It’s not the type of the vertex data itself.Īs for documentation: There is (of course) a Reference Manual - the specification of WebGL - however, because WebGL is almost identical to OpenGL-ES-2.0, it mostly refers to the OpenGL-ES-2.0 spec. In WebGL, it should always be UNSIGNED_SHORT. The third parameter of drawElements is the type of the index array. If it doesn’t work, then…I dunno…maybe you’ve found a bug in the driver or something.If that works - then you have a starting point for a program that draws lines.…make a copy and change the gl.drawElements call to draw the teapot as line loops. If this test doesn’t work then take one of the demo programs like “shineyteapot” over at: If it doesn’t - then there is something very strange going on - probably something else entirely. That should draw that exact same triangle as three lines. In theory: Take your program that draws a single triangle successfully - and change the first parameter of the drawElements function to gl.LINE_LOOP…change NOTHING else.

I don’t think the other traditional OpenGL method (to set the fill mode for polygons to “GL_LINE”) works in OpenGL-ES or WebGL. Hence it is unwise to rely on having variable width lines in practice. In theory, you can use gl.lineWidth(x) to set the width of the line in pixels - but on MS Windows systems that are using Direct3D “under the hood”, the MAX_LINE_WIDTH constant is probably set to 1.0 because Direct3D doesn’t support variable width lines. In the gl.LINE_STRIP case, the system will connect up all of the vertices into one long series of connected lines - and in the gl.LINE_LOOP case it’ll also connect the last point back to the first to make a loop. In the gl.LINES case, every pair of vertices in your input data will be connected to make a line between them (just like every group of three are connected to make a triangle with gl.TRIANGLES). In your “drawElements” call, change the first parameter from gl.TRIANGLES (or whatever it is) to gl.LINES, gl.LINE_STRIP or gl.LINE_LOOP.

Opengl es 2.0 drawelements line