Some snippets from my povriter code

code.java

    /**
     * beginRaw and endRaw should wrap what you want to ray-trace
     */
    public void endRaw() {
        if (this.getState(State.RECORDING)) {

            parent.endRaw();
            this.setState(State.RECORDED);
            out.println(String.format(INFO_FORMAT, State.RECORDED));
        }
        if ((this.getState(State.RECORDED)) && (povray == null)) {
            povray = this.rayTrace();
            if (povray != null) {
                out.println(String.format(INFO_FORMAT, State.TRACING));
                this.setState(State.TRACING);
            }
        }
        try {
            if ((this.getState(State.TRACING)) && povray.waitFor() == 0) {
                this.setState(State.TRACED);      // set State as TRACED when povray has finished
                out.println(String.format(INFO_FORMAT, State.TRACED));
            }
        } catch (InterruptedException ex) {
            Logger.getLogger(PovExporter.class.getName()).log(Level.SEVERE, null, ex);
        } // following matches previous pushMatrix() needed to place button
        parent.popMatrix();
    }


public Process rayTrace() {

        if (iniFile != null) {
            try {
                String[] args = new String[]{povrayPath, iniFile};
                povray = new ProcessBuilder(args).start();
                redirect(povray.getErrorStream());
            } catch (IOException ex) {
                Logger.getLogger(PovExporter.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
        return povray;
    }


private static void redirect(InputStream in) throws IOException {
        int c;
        while ((c = in.read()) != -1) {
            out.write((char) c);
        }
    }