OpenGL绘制了数千个2D圆圈

Question

In my application, I am rendering thousands (~10k) 2D circles on top of a 3D scene. I have it working, but the performance is very slow when there are this many circles (the circles are small, ~16 pixels diameter). My code for drawing the circles looks like:

for ( int i = 0; i < numCircles; i++) {
    int attributeMask = GL.GL_DEPTH_BUFFER_BIT | GL.GL_TRANSFORM_BIT
            | GL.GL_VIEWPORT_BIT | GL.GL_CURRENT_BIT
            | GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT
            | GL.GL_ENABLE_BIT | GL.GL_LIGHTING_BIT;
    gl.glPushAttrib(attributeMask);
    gl.glMatrixMode(GL.GL_PROJECTION);
    gl.glDisable(GL.GL_LIGHTING);
    gl.glPushMatrix();
    gl.glLoadIdentity();
    gl.glOrtho(0d, dc.getView().getViewport().width, 0d, dc.getView()
            .getViewport().height, -1, 1);

    gl.glMatrixMode(GL.GL_MODELVIEW);
    gl.glPushMatrix();
    gl.glLoadIdentity();
    gl.glDisable(GL.GL_DEPTH_TEST);

    Vec4 screenPt // this is calculated for each circle
    double size = 16;
    gl.glTranslated(screen.x, screen.y, 0d);
    gl.glScaled(size, size, size);

    gl.glCallList(fillListId);
    gl.glCallList(outlineListId);

    gl.glMatrixMode(GL.GL_MODELVIEW);
    gl.glPopMatrix();
    gl.glMatrixMode(GL.GL_PROJECTION);
    gl.glPopMatrix();
    gl.glPopAttrib();
}

The lists are generated as follows:

    NUM_SEGMENTS = 18;
    double[][] vertices = new double[2][NUM_SEGMENTS];
    for (int i = 0; i < NUM_SEGMENTS; i++)
    {
        double rad = -2 * Math.PI * ((double) i) / ((double) NUM_SEGMENTS);
        double x = Math.cos(rad);
        double y = Math.sin(rad);
        vertices[0][i] = x;
        vertices[1][i] = y;
    }

    gl.glNewList(id, GL.GL_COMPILE);
    gl.glBegin(GL.GL_LINE_LOOP); // 2 lists are actually created, the first time GL.GL_LINE_LOOP IS is used for the outline, and the second time GL.GL_POLYGON is used for the fill
    for (int j = 0; j < vertices[0].length; j++)
    {
        gl.glVertex2d(vertices[0][j], vertices[1][j]);
    }
    gl.glEnd();
    gl.glEndList();

Is there something I'm doing obviously wrong here to slow down the rendering? Should I consider using vertex buffers here? Or are there other techniques to speed this up?

Thanks, Jeff

Answer 1

您可以生成一个圆圈，将其blit到纹理，然后只创建用该圆圈纹理化的（两个三角形）曲面。

Answer 2

I would think all of this code

int attributeMask = GL.GL_DEPTH_BUFFER_BIT | GL.GL_TRANSFORM_BIT
        | GL.GL_VIEWPORT_BIT | GL.GL_CURRENT_BIT
        | GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT
        | GL.GL_ENABLE_BIT | GL.GL_LIGHTING_BIT;
gl.glPushAttrib(attributeMask);
gl.glMatrixMode(GL.GL_PROJECTION);
gl.glDisable(GL.GL_LIGHTING);
gl.glPushMatrix();
gl.glLoadIdentity();
gl.glOrtho(0d, dc.getView().getViewport().width, 0d, dc.getView()
        .getViewport().height, -1, 1);

gl.glMatrixMode(GL.GL_MODELVIEW);
gl.glPushMatrix();
gl.glLoadIdentity();
gl.glDisable(GL.GL_DEPTH_TEST);

and all of this code

gl.glMatrixMode(GL.GL_MODELVIEW);
gl.glPopMatrix();
gl.glMatrixMode(GL.GL_PROJECTION);
gl.glPopMatrix();
gl.glPopAttrib();

could be done outside of the loop, and just done once.

You would just need to push and pop a matrix for the object translate/scale.