Unity GL 实时绘制

GL立即绘图

• 挂载到GameObject上即可
  • OnRenderObject // 都可以显示
  • OnGUI // Game模式可以显示，Editor不显示

矩阵

• GL.PushMatrix(); // 保存摄像机变换矩阵
  • GL.LoadPixelMatrix() // 设置用屏幕坐标绘图
  • GL.MultMatrix()
• GL.PopMatrix(); // 还原

绘制模式

• GL.Begin()
  • Primitive
    • GL.QUADS
    • GL.LINES
    • GL.LINE_STRIP
    • GL.TRIANGLES
    • GL.TRIANGLE_STRIP
  • GL.Vertex3()
• GL.End()

代码结构

void OnRenderObject()
{
    GL.PushMatrix();
    Color clr = Color.green;
    clr.a = 0.1f;
    GL.MultMatrix(transform.localToWorldMatrix);

    GL.PopMatrix();
}

参考

• Three ways to draw wireframe – 三種繪製線框做法
• Unity中GL类的使用简记
• unity使用GL在场景绘制网格

代码

using UnityEngine;

public static class DrawGL
{
    public enum DrawMode : int
    {
        Line = GL.LINES,
        LineStrip = GL.LINE_STRIP,
        Triangle = GL.TRIANGLES,
        TriangleStrip = GL.TRIANGLE_STRIP,
        Quad = GL.QUADS
    }

    static Material drawMaterial;

    static void InitMaterial()
    {
        if (!drawMaterial)
        {
            Shader shader = Shader.Find("Hidden/Internal-Colored");
            drawMaterial = new Material(shader);
            drawMaterial.hideFlags = HideFlags.HideAndDontSave;
        }
    }

    public static void WireframeMode(float zBias = 0, bool bAlpha = false, bool bZTest = true, int cullMode = 0)
    {
        InitMaterial();
        if (bAlpha)
        {
            drawMaterial.SetInt("_SrcBlend", (int) UnityEngine.Rendering.BlendMode.SrcAlpha);
            drawMaterial.SetInt("_DstBlend", (int) UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
        }
        else
        {
            drawMaterial.SetInt("_SrcBlend", (int) UnityEngine.Rendering.BlendMode.One);
            drawMaterial.SetInt("_DstBlend", (int) UnityEngine.Rendering.BlendMode.Zero);
        }

        drawMaterial.SetInt("_Cull", cullMode); // Off=0 Front=1 Back=2
        drawMaterial.SetInt("_ZWrite", 0); // Turn off depth writes

        var zTest = bZTest
            ? UnityEngine.Rendering.CompareFunction.LessEqual
            : UnityEngine.Rendering.CompareFunction.Always;
        drawMaterial.SetInt("_ZTest", (int) zTest);
        drawMaterial.SetFloat("_ZBias", zBias);

        drawMaterial.SetPass(0);
    }

    public static void DrawMesh(Mesh mesh, Matrix4x4 matrix, Color color, float zBias = 0)
    {
        Vector3[] vertices = mesh.vertices;
        int[] triangles = mesh.triangles;

        WireframeMode(zBias);
        GL.PushMatrix();
        GL.MultMatrix(matrix);

        GL.Begin(GL.LINES);
        GL.Color(color);
        for (int cnt = 0; cnt < triangles.Length; cnt += 3)
        {
            GL.Vertex(vertices[triangles[cnt]]);
            GL.Vertex(vertices[triangles[cnt + 1]]);
            GL.Vertex(vertices[triangles[cnt + 1]]);
            GL.Vertex(vertices[triangles[cnt + 2]]);
            GL.Vertex(vertices[triangles[cnt + 2]]);
            GL.Vertex(vertices[triangles[cnt]]);
        }

        GL.End();
        GL.PopMatrix();
    }
}