c++ - 在 OpenGL 中渲染一组三角形结构引用

Question

我有一个 std::vector<Triangle*>我试图在 OpenGL 中渲染。我的 vector 定义为:

#pragma once

#include <glm\glm.hpp>

struct Triangle
{
    glm::vec3 _vertex0, _vertex1, _vertex2;
    Triangle(glm::vec3 vertex0, glm::vec3 vertex1, glm::vec3 vertex2)
    {
        _vertex0 = vertex0;
        _vertex1 = vertex1;
        _vertex2 = vertex2;
    }

    Triangle(glm::vec4 vertex0, glm::vec4 vertex1, glm::vec4 vertex2)
    {
        _vertex0 = glm::vec3(vertex0.x, vertex0.y, vertex0.z);
        _vertex1 = glm::vec3(vertex1.x, vertex1.y, vertex1.z);
        _vertex2 = glm::vec3(vertex2.x, vertex2.y, vertex2.z);
    }
};

我的 Asset struct是:

struct Asset
{
    Asset() { }
    Asset(std::string assetOBJFile)
    {
        glGenVertexArrays(1, &vertexArrayID);
        glBindVertexArray(vertexArrayID);

        programID = LoadShaders("vertexShader.txt", "fragmentShader.txt");

        // Read our .obj file
        loadOBJ(assetOBJFile.c_str(), originalTriangles, vertices, faces);

        boundingSphere = BoundingSphere(vertices);

        // Load it into a VBO
        glGenBuffers(1, &vertexbuffer);
        glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
        glBufferData(GL_ARRAY_BUFFER, originalTriangles.size() * sizeof(Triangle), &originalTriangles[0], GL_STATIC_DRAW);

        //velocity = glm::vec3(0.0, 1.0, 1.0);
        velocity = glm::vec3(0.0, 0.0, 0.0);
        position = glm::vec3(0.0, 0.0, 0.0);

        lastTime = glfwGetTime();
    }

    GLuint vertexArrayID;
    GLuint programID;

    GLuint vertexbuffer;

    std::vector<GLuint> faces;
    std::vector<glm::vec3> vertices;
    std::vector<Triangle*> originalTriangles;
    std::vector<Triangle*> triangles;

    BoundingSphere boundingSphere;

    glm::vec3 velocity;

    double lastTime;
    glm::vec3 position;
};

我渲染 Assets 的代码是:

void renderAsset(Asset asset)
{   
    glUseProgram(asset.programID);

    GLuint cameraID = glGetUniformLocation(asset.programID, "camera");
    glUniformMatrix4fv(cameraID, 1, GL_FALSE, &camera[0][0]);

    GLuint positionID = glGetUniformLocation(asset.programID, "position");
    glUniformMatrix4fv(positionID, 1, GL_FALSE, &glm::translate(glm::mat4(), asset.position)[0][0]);

    glEnableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER, asset.vertexbuffer);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
    glDrawArrays(GL_TRIANGLES, 0, asset.originalTriangles.size()* 9);

    glDisableVertexAttribArray(0);
}

但是，当我尝试渲染 Assets 时，我最终只会在屏幕上看到一堆乱码。如果我更改 Triangle* 的 vector 至 Triangle一切都很好，但我需要指针来构建我的空间散列。

Answer 1

您需要展平三角形 vector 。您现在将一个指针数组传递给 glBufferData，而不是您想要实际数据。

Triangle flattenedTriangles[] = new Triangle[ originalTriangles.size() ];
for(int i = 0; i<originalTriangles.size(); i++){
    flattenedTriangles[i] = *(originalTriangles[i]);
}

glBufferData(GL_ARRAY_BUFFER, originalTriangles.size() * sizeof(Triangle), &flattenedTriangles[0], GL_STATIC_DRAW);
delete[] flattenedTriangles;

或者如果您不想分配数组而是映射缓冲区并就地构造:

glBufferData(GL_ARRAY_BUFFER, originalTriangles.size() * sizeof(Triangle), 0, GL_STATIC_DRAW);//allocate
do{
Triangle *flattenedTriangles = (flattenedTriangles*)glMapBuffer(GL_ARRAY_BUFFER,GL_WRITE_ONLY);
for(int i = 0; i<originalTriangles.size(); i++){
        flattenedTriangles[i] = *(originalTriangles[i]);
    }
}while(glUnmapBuffer(GL_ARRAY_BUFFER));//repeat if map got invalidated