如何在OpenGL中绘制点的轮廓? [英] How to draw outline of a point in OpenGL?

问题描述

现在可以使用以下代码绘制点:

By now points can be drawn with the following code:

    // SETUP FOR VERTICES
GLfloat points[graph->vertexCount * 6];
for (int i = 0 ; i < graph->vertexCount; i++) 
{
    points[i*6] = (graph->vertices[i].x / (backingWidth/2) ) - 1;
    points[i*6+1] = -(graph->vertices[i].y / (backingHeight/2) ) + 1;

    points[i*6+2] = 1.0;
    points[i*6+3] = 0.0;
    points[i*6+4] = 0.0;
    points[i*6+5] = 1.0;
}

glEnable(GL_POINT_SMOOTH);
glPointSize(DOT_SIZE*scale); 
glVertexPointer(2, GL_FLOAT, 24, points);
glColorPointer(4, GL_FLOAT, 24, &points[2]);
glDrawArrays(GL_POINTS, 0, graph->vertexCount);

这些点用红色渲染，我想在这些点之外添加白色轮廓.如何绘制该点的轮廓?

The points are rendered with red color, and I want to add a white outline outside the points. How can I draw outline of the point?

问题，以更好地显示

按照@BDL的说明在红色点下方添加较大的点作为轮廓，它们看起来不错.

Follow @BDL 's instruction adding bigger points under the red points as outline, they look good.

outlinePoints[i*6] = (graph->vertices[i].x / (backingWidth/2) ) - 1;
outlinePoints[i*6+1] = -(graph->vertices[i].y / (backingHeight/2) ) + 1;
outlinePoints[i*6+2] = 0.9;
outlinePoints[i*6+3] = 0.9;
outlinePoints[i*6+4] = 0.9;
outlinePoints[i*6+5] = 1.0;

但是当一个点与另一点重叠时，其轮廓被红色点覆盖，因为轮廓点在所有红色点之前绘制.

But when one point overlaps another point, it's outline is covered by the red point, since the outline points are rendered before all the red points.

我认为正确的解决方案是逐个渲染一个轮廓点和一个红色点.该怎么做?

I think the right solution is to render one outline point and red point one by one. How to do that?

推荐答案

如果要分别绘制每个点的轮廓，则可以先简单地渲染一个稍大的白点，然后在其上渲染红色点.启用深度测试后，您可能需要在渲染红点时调整多边形的偏移量，以防止它们隐藏在白点之后.

If you want to render outlines for each point separately, then you can simply render a slightly larger white point first and then render the red point over it. With depth-testing enabled, you might have to adjust the polygon offset when rendering the red point to prevent them from getting hidden behind the white ones.

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