JOGL 中的文本困难

Question

我正在尝试在我的 OpenGL / JOGL 应用程序中显示文本。以下是部分代码：

private void display(GLAutoDrawable drawable) {
    GL2 gl = drawable.getGL().getGL2();
    GLUgl2 glu = new GLUgl2();

    float[] rgba = new float[4];
    backgroundColor.getRGBComponents(rgba);
    gl.glClearColor(rgba[0], rgba[1], rgba[2], 1);
    gl.glClear(GL2.GL_COLOR_BUFFER_BIT | GL2.GL_DEPTH_BUFFER_BIT);

    gl.glMatrixMode(GL2.GL_MODELVIEW);
    gl.glLoadIdentity();


    // Position the camera
    glu.gluLookAt(cameraPos.x, cameraPos.y, cameraPos.z, cameraPos.x + cameraForward.x, cameraPos.y + cameraForward.y,
            cameraPos.z + cameraForward.z, cameraUp.x, cameraUp.y, cameraUp.z);

    gl.glPushMatrix();
    GLUT glut = new GLUT();
    gl.glTranslatef(0, 0, 0);
    gl.glColor3f(1, 0, 0);
    glut.glutBitmapString(GLUT.BITMAP_HELVETICA_18, "We're going to the moon!");
    gl.glPopMatrix();

    // ...

文本在渲染开始后立即出现，然后从屏幕右侧消失。为什么会这样？

我想在用户面前显示文字，而不是作为世界上的模型。

Answer 1

您需要在调用glutBitmapString 之前设置当前光栅位置。光栅位置是开始绘制字符串的像素。您可以使用glRasterPos... 系列函数对其进行设置。您的文本似乎“跑出”屏幕右侧的原因是调用glutBitmapString 隐式地将光栅位置移动到字符串的末尾（请参阅here）。

Answer 2

有一个非常简单的解决方案，但它会将您的应用与 awt “链接”，如果您试图远离它而支持 newt，这可能会很糟糕。

以下示例使用多个文本渲染器绘制播放器 osd：一个用于播放/暂停字形，一个用于时间等信息，另一个用于电影名称。

    import com.jogamp.opengl.util.awt.TextRenderer;

    private static final Color DROP_SHADOW_COLOR = new Color(0, 0, 0, 0.5f);

    class CustomRenderDelegate implements TextRenderer.RenderDelegate {
        private int dropShadowDepth;
        private Color color;

        CustomRenderDelegate(int dropShadowDepth, Color color) {
            this.dropShadowDepth = dropShadowDepth;
            this.color = color;
        }

        public boolean intensityOnly() {
            return false;
        }

        public Rectangle2D getBounds(CharSequence str, Font font, FontRenderContext frc) {
            return getBounds(str.toString(), font, frc);
        }

        public Rectangle2D getBounds(String str, Font font, FontRenderContext frc) {
            return getBounds(font.createGlyphVector(frc, str), frc);
        }

        public Rectangle2D getBounds(GlyphVector gv, FontRenderContext frc) {
            Rectangle2D stringBounds = gv.getPixelBounds(frc, 0, 0);
            return new Rectangle2D.Double(stringBounds.getX(), stringBounds.getY(), stringBounds.getWidth()
                    + dropShadowDepth, stringBounds.getHeight() + dropShadowDepth);
        }

        public void drawGlyphVector(Graphics2D graphics, GlyphVector str, int x, int y) {
            graphics.setColor(DROP_SHADOW_COLOR);
            graphics.drawGlyphVector(str, x + dropShadowDepth, y + dropShadowDepth);
            graphics.setColor(color);
            graphics.drawGlyphVector(str, x, y);
        }

        public void draw(Graphics2D graphics, String str, int x, int y) {
            graphics.setColor(DROP_SHADOW_COLOR);
            graphics.drawString(str, x + dropShadowDepth, y + dropShadowDepth);
            graphics.setColor(color);
            graphics.drawString(str, x, y);
        }
    }

    public void init(GLAutoDrawable drawable) {
            ...
            pathRenderer = new TextRenderer(new Font("Helvetica", Font.ITALIC, 16), true, true, new CustomRenderDelegate(0,
                Color.WHITE));
        pathRenderer.setSmoothing(true);

        playRenderer = new TextRenderer(new Font("Helvetica", Font.BOLD, 65), true, true, new CustomRenderDelegate(0,
                Color.WHITE));
        pauseRenderer = new TextRenderer(new Font("Helvetica", Font.BOLD, 50), true, true, new CustomRenderDelegate(0,
                Color.WHITE));

        osdRenderer = new TextRenderer(new Font("Helvetica", Font.PLAIN, 32), true, true, new CustomRenderDelegate(0,
                Color.WHITE));
        osdRenderer.setSmoothing(true);
    }

    private final void updateOsd() {
        Time t = currentFrame != null ? currentFrame.getTime() : new Time(0, 0, 0, 0, 0);
        String direction = video.direction == DirectionType.DIRECTION_LEFT ? "<" : ">";
        String frameNumber = enterFrameNumber != null ? String.format("[%s]", enterFrameNumber)
                : String.format("(%d)", t.fn);
        osdText = String.format(" %s%s x %d @ %.2f fps < %d/%d (%s) @ %d fps", TimeUtil.hmsms(t.getPtsMillis()), frameNumber, (int) video.getPlaybackRate(), playbackFps, video.readyFrames(), maxFrames, direction, video.getFilterFps());
    }

    private void renderOsd(GLAutoDrawable drawable) {
        updateOsd();

        if (isOsdEnabled) {
            maxModeWidth = (int) Math.max(maxModeWidth, playRenderer.getBounds("\u25B8").getWidth());
            maxOsdHeight = (int) Math.max(maxOsdHeight, playRenderer.getBounds("\u25B8").getHeight());

            if (isPaused) {
                pauseRenderer.beginRendering(drawable.getWidth(), drawable.getHeight());
                pauseRenderer.draw("\u2759", 10, drawable.getHeight() - maxOsdHeight - 2);
                int barWidth = (int) pauseRenderer.getBounds("\u2759").getWidth();
                pauseRenderer.draw("\u2759", 10 + barWidth - 3, drawable.getHeight() - maxOsdHeight - 2);
                pauseRenderer.flush();
                pauseRenderer.endRendering();
            } else {
                playRenderer.beginRendering(drawable.getWidth(), drawable.getHeight());
                playRenderer.draw("\u25B8", 10, drawable.getHeight() - maxOsdHeight - 5);
                playRenderer.flush();
                playRenderer.endRendering();
            }

            int y = (int) ((maxOsdHeight + 10) - osdRenderer.getBounds(osdText).getHeight() / 2);
            osdRenderer.beginRendering(drawable.getWidth(), drawable.getHeight());
            osdRenderer.draw(osdText, maxModeWidth + 18, drawable.getHeight() - y - 2);
            osdRenderer.flush();
            osdRenderer.endRendering();

            if (isFullScreen) {
                pathRenderer.beginRendering(drawable.getWidth(), drawable.getHeight());
                pathRenderer.draw(videoFile.getName(), 18, drawable.getHeight() - y - maxOsdHeight + 15);
                pathRenderer.flush();
                pathRenderer.endRendering();
            }
        }
    }


    public void display(GLAutoDrawable drawable) {
        GL gl = drawable.getGL();
        gl.glClear(GL.GL_COLOR_BUFFER_BIT);
        gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        renderFrame(drawable);
        renderOsd(drawable);
        gl.glFinish();
    }