使用 OpenGL 绘制图像

Question

如何在打开 OpenGL/OpenTK 的情况下在地图 (GMap.Net) 上绘制 video/image（来自无人机的视频）

我的问题是如何在地图上绘制视频图像，因为视频可以在地图上以不同的角度观看，图像在地图上应该是梯形而不是四边形？

我从其他问题复制了图像...目前我的代码在下面绘制四边形，但在四边形中我看到 2 个不相等的三角形。

当前代码：

public override void OnRender()
{
    if (!backgroundColor.HasValue)
        backgroundColor = new Pen(Fill).Color;
    GL.Color4(backgroundColor.Value);

    lock (bitmapSync)
    {
        if (bitmap != null)
            createTexture();
    }

    GL.Enable(EnableCap.Texture2D);
    GL.BindTexture(TextureTarget.Texture2D, texture);

    GL.Begin(PrimitiveType.Quads);
    {
        //TODO this works fine only for correct square image and not for trapezoid 
        GL.TexCoord2(0, 0); GL.Vertex2(LocalPoints[0].X, LocalPoints[0].Y);
        GL.TexCoord2(1, 0); GL.Vertex2(LocalPoints[1].X, LocalPoints[1].Y);
        GL.TexCoord2(1, 1); GL.Vertex2(LocalPoints[2].X, LocalPoints[2].Y);
        GL.TexCoord2(0, 1); GL.Vertex2(LocalPoints[3].X, LocalPoints[3].Y);
    }
    GL.End();
    GL.Disable(EnableCap.Texture2D);

    float wid = Stroke.Width;
    Color col = Stroke.Color;

    if (wid > 0)
    {
        for (int i = 0; i < LocalPoints.Count; i++)
        {
            int j = (i + 1) % LocalPoints.Count;
            GMapControl.line(LocalPoints[i].X, LocalPoints[i].Y, LocalPoints[j].X, LocalPoints[j].Y, wid, col);
        }
    }
}

答案位于 Perspective correct texturing of trapezoid in OpenGL ES 2.0 http://www.reedbeta.com/blog/quadrilateral-interpolation-part-1/ https://gamedev.stackexchange.com/questions/68021/how-can-i-draw-a-perspective-correct-quad How to texture a random convex quad in openGL 没有帮助...

Answer 1

我找到了四边形透视校正的解决方案

public override void OnRender()
{
    if (LocalPoints.Count == 4 && !targetPosition.IsEmpty)
    {
        if (!backgroundColor.HasValue)
            backgroundColor = new Pen(Fill).Color;
        GL.Color4(backgroundColor.Value);

        lock (bitmapSync)
        {
            if (bitmap != null)
                createTexture();
        }

        GL.Enable(EnableCap.Texture2D);
        GL.BindTexture(TextureTarget.Texture2D, texture);

        // center point
        GPoint localTargetPosition = MainForm.instance.gMapControl.FromLatLngToLocalWithOffset(targetPosition);
        // determines distances to center for all vertexes
        double dUL = Common.distance(new double[] { LocalPoints[0].X, LocalPoints[0].Y }, new double[] { localTargetPosition.X, localTargetPosition.Y });
        double dUR = Common.distance(new double[] { LocalPoints[1].X, LocalPoints[1].Y }, new double[] { localTargetPosition.X, localTargetPosition.Y });
        double dLR = Common.distance(new double[] { LocalPoints[2].X, LocalPoints[2].Y }, new double[] { localTargetPosition.X, localTargetPosition.Y });
        double dLL = Common.distance(new double[] { LocalPoints[3].X, LocalPoints[3].Y }, new double[] { localTargetPosition.X, localTargetPosition.Y });

        var texCoords = new[]
        {
            new Vector4(0, 0, 1, 1),
            new Vector4(1, 0, 1, 1),
            new Vector4(1, 1, 1, 1),
            new Vector4(0, 1, 1, 1)
        };

        texCoords[0] *= (float)((dUL + dLR) / dLR);
        texCoords[1] *= (float)((dUR + dLL) / dLL);
        texCoords[2] *= (float)((dLR + dUL) / dUL);
        texCoords[3] *= (float)((dLL + dUR) / dUR);

        GL.Begin(PrimitiveType.Quads);
        {
            //GL.TexCoord2(0, 0); //UL  LocalPoints[0] gimbalUL
            //GL.TexCoord2(1, 0); //UR  LocalPoints[1] gimbalUR
            //GL.TexCoord2(1, 1); //LR  LocalPoints[2] gimbalLR
            //GL.TexCoord2(0, 1); //LL  LocalPoints[3] gimbalLL
            GL.TexCoord4(texCoords[0]); GL.Vertex4(LocalPoints[0].X, LocalPoints[0].Y, 1, 1);
            GL.TexCoord4(texCoords[1]); GL.Vertex4(LocalPoints[1].X, LocalPoints[1].Y, 1, 1);
            GL.TexCoord4(texCoords[2]); GL.Vertex4(LocalPoints[2].X, LocalPoints[2].Y, 1, 1);
            GL.TexCoord4(texCoords[3]); GL.Vertex4(LocalPoints[3].X, LocalPoints[3].Y, 1, 1);
        }

        GL.End();
        GL.Disable(EnableCap.Texture2D);

        float wid = Stroke.Width;
        Color col = Stroke.Color;

        if (wid > 0)
        {
            for (int i = 0; i < LocalPoints.Count; i++)
            {
                int j = (i + 1) % LocalPoints.Count;
                GMapControl.line(LocalPoints[i].X, LocalPoints[i].Y, LocalPoints[j].X, LocalPoints[j].Y, wid, col);
            }
        }
    }
    else
    {
        base.OnRender();
    }

}

使用 OpenGL 绘制图像

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