OpenGL实例化数组奇怪的顶点位置

Question

从使用 VBO/VAO 的普通绘图切换到使用 VBO/VAO 的实例化数组后，我无法从 OpenGL 应用程序获取正确的输出。输出应该是一堆球体，但它是疯狂定位的顶点，形成奇怪的三角形。我检查了调试器控制台中的顶点位置，但似乎没有任何可疑之处。它们都在 -10 到 10 的范围内，在场景中它们可能会达到 +/-30。

这是我的代码的重要部分。如果我没有看到任何东西，请告诉我。我将不胜感激！

char const *attribInSphereModelMatrix = "inSphereModelMatrix";
std::vector<glm::mat4> dNodesModelMatrices;

...

attributes[ATTRIB_SPHERE_MODEL_COLUMN0] = shader->getAttribLocation(attribInSphereModelMatrix);
attributes[ATTRIB_SPHERE_MODEL_COLUMN1] = attributes[ATTRIB_SPHERE_MODEL_COLUMN0] + 1;
attributes[ATTRIB_SPHERE_MODEL_COLUMN2] = attributes[ATTRIB_SPHERE_MODEL_COLUMN0] + 2;
attributes[ATTRIB_SPHERE_MODEL_COLUMN3] = attributes[ATTRIB_SPHERE_MODEL_COLUMN0] + 3;

...

// Create the vertex array object
glGenVertexArrays(1, &sphereVertexArray);
glBindVertexArray(sphereVertexArray);

// Create the buffer object to hold the sphere view matrix
glGenBuffers(1, &sphereModelMatrixBuffer);
glBindBuffer(GL_ARRAY_BUFFER, sphereModelMatrixBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(glm::mat4) * dNodes.size(), &dNodesModelMatrices[0], GL_STATIC_DRAW);

// All matrix data is in one VBO, set the appropriate offsets
glEnableVertexAttribArray(attributes[ATTRIB_SPHERE_MODEL_COLUMN0]);
glVertexAttribPointer(attributes[ATTRIB_SPHERE_MODEL_COLUMN0], 4, GL_FLOAT, GL_FALSE, sizeof(glm::mat4), NULL);
glVertexAttribDivisorARB(attributes[ATTRIB_SPHERE_MODEL_COLUMN0], 1);

glEnableVertexAttribArray(attributes[ATTRIB_SPHERE_MODEL_COLUMN1]);
glVertexAttribPointer(attributes[ATTRIB_SPHERE_MODEL_COLUMN1], 4, GL_FLOAT, GL_FALSE, sizeof(glm::mat4), (const GLvoid *)(sizeof(glm::vec4)));
glVertexAttribDivisorARB(attributes[ATTRIB_SPHERE_MODEL_COLUMN1], 1);

glEnableVertexAttribArray(attributes[ATTRIB_SPHERE_MODEL_COLUMN2]);
glVertexAttribPointer(attributes[ATTRIB_SPHERE_MODEL_COLUMN2], 4, GL_FLOAT, GL_FALSE, sizeof(glm::mat4), (const GLvoid *)(2 * sizeof(glm::vec4)));
glVertexAttribDivisorARB(attributes[ATTRIB_SPHERE_MODEL_COLUMN2], 1);

glEnableVertexAttribArray(attributes[ATTRIB_SPHERE_MODEL_COLUMN3]);
glVertexAttribPointer(attributes[ATTRIB_SPHERE_MODEL_COLUMN3], 4, GL_FLOAT, GL_FALSE, sizeof(glm::mat4), (const GLvoid *)(3 * sizeof(glm::vec4)));
glVertexAttribDivisorARB(attributes[ATTRIB_SPHERE_MODEL_COLUMN3], 1);

一旦我准备好设置，我就会去绘图。

glEnableVertexAttribArray(attributes[ATTRIB_SPHERE_MODEL_COLUMN0]);
glEnableVertexAttribArray(attributes[ATTRIB_SPHERE_MODEL_COLUMN1]);
glEnableVertexAttribArray(attributes[ATTRIB_SPHERE_MODEL_COLUMN2]);
glEnableVertexAttribArray(attributes[ATTRIB_SPHERE_MODEL_COLUMN3]);

...

glDrawElementsInstanced(GL_TRIANGLES, numSphereTris, GL_UNSIGNED_INT, NULL, (int)dNodes.size());

这里是顶点着色器的重要部分：

in mat4 inSphereModelMatrix;

...

void main()
{
    vec4 v = vec4(inPosition, 1.0);
    mat4 modelViewMatrix = viewMatrix * inSphereModelMatrix;

    ...

    gl_Position = projectionMatrix * modelViewMatrix * v;
}

结果如下：

请以某种方式帮助我。在过去的 3 天里，我一直在为此苦苦挣扎。谢谢大家！

编辑：我一直想知道它是否与列/行主要顺序有关，所以我尝试转置矩阵，但我得出的结论不是导致的问题。

Answer 1

我明白了！我尝试在着色器中使用纹理缓冲区对象和gl_InstanceID 来实际获取矩阵列，并且它有效！我不敢相信与我之前所做的相同的事情怎么会不起作用，并且使用纹理缓冲区对象 (TBO) 是如何起作用的……但是，我将发布代码的重要部分以供将来参考。

/// A texture buffer object to pass to the shaders
GLuint sphereModelMatrixTBO;

/// A texture holding the matrices data
GLuint sphereModelMatrixTex;
.
.
.
/// Vector containing the model matrices of the spheres
std::vector<glm::mat4> dNodesModelMatrices;
.
.
.
glGenBuffers(1, &sphereModelMatrixTBO);
glBindBuffer(GL_TEXTURE_BUFFER, sphereModelMatrixTBO);
glBufferData(GL_TEXTURE_BUFFER, sizeof(glm::mat4) * dNodes.size(), &dNodesModelMatrices[0], GL_STATIC_DRAW);

在绘图例程中，我执行以下操作：

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_BUFFER, sphereModelMatrixTex);
glTexBuffer(GL_TEXTURE_BUFFER, GL_RGBA32F, sphereModelMatrixTBO);

glUniform1i(uniforms[UNIFORM_MODEL_MATRIX_BUFFER], 0);
.
.
.
glDrawElementsInstanced(GL_TRIANGLES, numSphereTris, GL_UNSIGNED_INT, NULL, (int)dNodes.size());

顶点着色器现在看起来如下：

uniform samplerBuffer sphereModelMatrixBuffer;
.
.
.
vec4 col1 = texelFetch(sphereModelMatrixBuffer, gl_InstanceID * 4);
vec4 col2 = texelFetch(sphereModelMatrixBuffer, gl_InstanceID * 4 + 1);
vec4 col3 = texelFetch(sphereModelMatrixBuffer, gl_InstanceID * 4 + 2);
vec4 col4 = texelFetch(sphereModelMatrixBuffer, gl_InstanceID * 4 + 3);
mat4 modelMatrix = mat4(col1, col2, col3, col4);

这就是拥有一个功能齐全的快速 OpenGL 应用程序所需要做的一切！这就是现在的样子：