I have successfully drawn gl.LINES in my adaptation of Eric's demogl1.ijs,
but each time I draw a new line that the user's command produces (for
example, say `forward 2` produces a line from 0,0,0 to 0,2,0) all of the
graphics on the incumbent canvas are erased, and that line (from 0,0,0 to
0,2,0) is all that shows. What can I do to keep the incumbent graphics to
stay and the new line to show, also?
Eric's code executes the function drawPrimitve() (see below) multiple times
with multiple lines and they all draw. The only differences are that
(1) when Eric does this, all of the calls to drawPrimitve() are in the same
function draw(), while my function is named drawLines(), and
(2) my function drawLines() is called after ajax stuff is used to get the
new line.
I have looked into lots of alternatives, but cannot see an answer myself.
function drawLines(linecolor,vertices) {
gl.lineWidth(4);
drawPrimitive( gl.LINES, linecolor, vertices);
gl.lineWidth(1);
}
// Copied directly from demogl1.ijs
function drawPrimitive( primitiveType, color, vertices ) {
gl.enableVertexAttribArray(aCoords);
gl.bindBuffer(gl.ARRAY_BUFFER,aCoordsBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices),
gl.STREAM_DRAW);
gl.uniform4fv(uColor, color);
gl.vertexAttribPointer(aCoords, 3, gl.FLOAT, false, 0, 0);
gl.drawArrays(primitiveType, 0, vertices.length/3);
}
Thanks,
--
(B=)
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