Question

我正在使用GLTools库中的GLBatch来绘制四面体。我想在不同位置多次绘制四面体以绘制Sierpinski-Tetrahedron。创建几何体并绘制锥体对四面体的一个实例工作正常，但我想在不同位置多次绘制四面体。多次调用geometry.Draw()（使用不同的模型视图矩阵）不起作用。锥体仍然只绘制一次。

如何多次绘制GLBatch？

这是我的代码：

GLBatch geometry;

// This is called once on initialization.    
void CreateTetrahedron()
{
    geometry.Begin(GL_TRIANGLE_STRIP, 6);

    geometry.Color4f(1, 0, 0, 1);
    geometry.Vertex3f(0, 1, 0);

    geometry.Color4f(1, 0, 0, 1);
    geometry.Vertex3f(-0.5f, 0, 0.5f);

    geometry.Color4f(1, 0, 0, 1);
    geometry.Vertex3f(0.5f, 0, 0.5f);

    if (recursionLevel < 3)
    {
        geometry.Color4f(0, 1, 0, 1);
        geometry.Vertex3f(0, 0, -0.7f);

        geometry.Color4f(0, 0, 1, 1);
        geometry.Vertex3f(0, 1, 0);

        geometry.Color4f(1, 1, 1, 1);
        geometry.Vertex3f(-0.5f, 0, 0.5f);
    }

    geometry.End();
}
// This is where I want to draw it. The function is recursive, and thus the geometry should be drawn multiple times with different matrices.
void DrawSierpinskiTetrahedron(UINT32 level)
{
    if (level == 0)
    {
        geometry.Draw();
    }
    else
    {
        modelViewMatrix.PushMatrix();
        modelViewMatrix.Scale(0.5f, 0.5f, 0.5f);

        modelViewMatrix.PushMatrix();
        modelViewMatrix.Translate(0, 1, 0);
        DrawSierpinskiTetrahedron(level - 1);
        modelViewMatrix.PopMatrix();

        modelViewMatrix.PushMatrix();
        modelViewMatrix.Translate(-0.5f, 0, 0.5f);
        DrawSierpinskiTetrahedron(level - 1);
        modelViewMatrix.PopMatrix();

        modelViewMatrix.PushMatrix();
        modelViewMatrix.Translate(0.5f, 0, 0.5f);
        DrawSierpinskiTetrahedron(level - 1);
        modelViewMatrix.PopMatrix();

        modelViewMatrix.PushMatrix();
        modelViewMatrix.Translate(0, 0, -0.7f);
        DrawSierpinskiTetrahedron(level - 1);
        modelViewMatrix.PopMatrix();

        modelViewMatrix.PopMatrix();
    }
}

void RenderScene(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    modelViewMatrix.PushMatrix();

    // Camera Translation
    modelViewMatrix.Translate(xTrans, yTrans, zTrans);

    // Model Translation, Rotatation und Scale
    glm::mat4 trans = glm::translate(glm::mat4(), translation);
    modelViewMatrix.MultMatrix(glm::value_ptr(trans));
    glm::mat4 rot = glm::mat4_cast(rotation);
    modelViewMatrix.MultMatrix(glm::value_ptr(rot));
    glm::mat4 sc = glm::scale(glm::mat4(), scale);
    modelViewMatrix.MultMatrix(glm::value_ptr(sc));

    // Set the shader for rendering
    shaderManager.UseStockShader(GLT_SHADER_FLAT_ATTRIBUTES, transformPipeline.GetModelViewProjectionMatrix());

    if (recursionLevel < 0)
    {
        recursionLevel = 0;
    }
    if (recursionLevel > 5)
    {
        recursionLevel = 5;
    }

    DrawSierpinskiTetrahedron(recursionLevel);

    gltCheckErrors(0);
    modelViewMatrix.PopMatrix();

    TwDraw();
    glutSwapBuffers();
    glutPostRedisplay();
}

// Initialize rendering context
void SetupRC()
{
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

    glFrontFace(GL_CW);
    glEnable(GL_CULL_FACE);
    glEnable(GL_DEPTH_TEST);

    shaderManager.InitializeStockShaders();
    transformPipeline.SetMatrixStacks(modelViewMatrix,projectionMatrix);

    // Create the geometry
    CreateTetrahedron();

    InitGUI();
}

更新

执行以下操作不会缩放四面体。

modelViewMatrix.PushMatrix();
modelViewMatrix.Scale(1000, 1000, 1000);
geometry.Draw();
modelViewMatrix.PopMatrix();

Answer 1

GLMatrixStack是一个类，它为堆栈的顶部矩阵提供矩阵堆栈和操作。

类GLShaderManager可以加载着色器并处理着色器的统一变量的设置。

着色器程序通过模型视图矩阵转换网格的顶点坐标。这导致mseh可以被渲染到场景中具有不同方向的不同位置。如果更改了模型视图矩阵，则必须在着色器程序中将其设置为相应的统一变量，以使更改起作用。这可以通过在绘制网格之前调用GLShaderManager::UseStockShader来完成。

像这样调整你的代码：

void DrawSierpinskiTetrahedron(UINT32 level)
{
    if (level == 0)
    {
        shaderManager.UseStockShader(GLT_SHADER_FLAT_ATTRIBUTES, transformPipeline.GetModelViewProjectionMatrix());
        geometry.Draw();
    }
    else
    {
        modelViewMatrix.PushMatrix();
        modelViewMatrix.Scale(0.5f, 0.5f, 0.5f);

        modelViewMatrix.PushMatrix();
        modelViewMatrix.Translate(0, 1, 0);
        DrawSierpinskiTetrahedron(level - 1);
        modelViewMatrix.PopMatrix();

        modelViewMatrix.PushMatrix();
        modelViewMatrix.Translate(-0.5f, 0, 0.5f);
        DrawSierpinskiTetrahedron(level - 1);
        modelViewMatrix.PopMatrix();

        modelViewMatrix.PushMatrix();
        modelViewMatrix.Translate(0.5f, 0, 0.5f);
        DrawSierpinskiTetrahedron(level - 1);
        modelViewMatrix.PopMatrix();

        modelViewMatrix.PushMatrix();
        modelViewMatrix.Translate(0, 0, -0.7f);
        DrawSierpinskiTetrahedron(level - 1);
        modelViewMatrix.PopMatrix();

        modelViewMatrix.PopMatrix();
    }
}

在不同位置多次绘制GLBatch

1 个答案: