我最近编写了一个程序来绘制具有3个不同RGB值的三角形，并且我希望在同一程序中对另一个单独的VAO进行同样的操作，但是我希望这个由5个三角形组成的三角形。这是我的main.cpp：
void framebuffer_size_callback(GFLWwindow* window, int width, int height);
void processInput(GLFWwindow *window);
// Shaders
const char *vertexShaderSource =
"#version 410\n"
"in vec3 vp;\n"
"void main()\n"
"{\n"
"gl_Position = vec4(aPos, 1.0);\n"
"}\0";
const char *fragmentShader1Source =
"#version 410\n"
"out vec4 FragColor;\n"
"in vec3 myColor;\n"
"void main()\n"
"{\n"
"FragColor = vec4(myColor, 1.0f);\n"
"}\n\0";
int main ()
{
// start GL context and O/S window using the GLFW helper library
if (!glfwInit ())
{
fprintf (stderr, "ERROR: could not start GLFW3\n");
return 1;
}
// uncomment these lines if on Apple OS X
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
GLFWwindow* window = glfwCreateWindow(640, 480, "LearnOpenGL", NULL, NULL);
if (!window)
{
fprintf(stderr, "ERROR: could not open window with GLFW3\n");
glfwTerminate();
return 1;
}
glfwMakeContextCurrent(window);
// start GLEW extension handler
glewExperimental = GL_TRUE;
glewInit();
// get version info
const GLubyte* renderer = glGetString(GL_RENDERER);
const GLubyte* version = glGetString(GL_VERSION);
printf("Renderer: %s\n", renderer);
printf("OpenGL version supported %s\n", version);
glEnable(GL_DEPTH_TEST); // enable depth-testing
glDepthFunc(GL_LESS);
/* OTHER STUFF GOES HERE */
// Draw a single triangle VBO
float points[] = {
// positions // colors
0.0f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f,
0.5f, -0.5f, 0.0f, 0.0f, 1.0f, 0.0f,
-0.5f, -0.5f, 0.0f, 0.0f 0.0f, 1.0f
};
GLuint VBO = 0;
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW);
// Generate a VAO.
GLuint VAO = 0;
glGenVertexArrays(1, &VAO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
glEnableVertexAttribArray(0);
// Compile a Vertex Shader
int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
// Compile a fragment shader.
int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
// Compile shaders into a executable shader program.
int shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, fragmentShader);
glAttachShader(shaderProgram, vertexShader);
glLinkProgram(shaderProgram);
// Drawing the triangles aka render loop
while (!glfwWindowShouldClose(window))
{
processInput(window);
// wipe the drawing surface clear
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Draw Triangle
glUseProgram(shaderProgram);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, 3);
// Draw Triangle Fan; unfinished
// swap buffers and poll IO events
glfwPollEvents();
glfwSwapBuffers(window);
}
// close GL context and any other GLFW resources
glfwTerminate();
return 0;
}
是否像我第一个VBO一样简单地创建另一个浮点数“点”矩阵？我所关注的教程在这一部分上并不十分清楚。
[此外，我在Mac上使用Xcode，我为Fragment和Vertex着色器创建了单独的.cpp文件。我应该将它们切换到头文件吗？
您可以通过创建另一个包含新点的float数组，以及创建另一个VAO和VBO来实现。由于您需要一个[[triangle fan（基于代码中的注释），而不是5个单独的三角形，因此可以这样：
float points_5_triangles[] = {
// positions // colors
// Original triangle
x1, y1, z1, r1, g1, b1, // point 1
x2, y2, z2, r2, g2, b2, // point 2
x3, y3, z3, r3, g3, b3, // point 3
// Another triangle made from point 1, 3 and 4
x4, y4, z4, r4, g4, b4,
// Another triangle made from point 1, 4 and 5
x5, y5, z5, r5, g5, b5,
// Another triangle made from point 1, 5 and 6
x6, y6, z6, r6, g6, b6,
// Another triangle made from point 1, 6 and 7
x7, y7, z7, r7, g7, b7,
};
GLuint VBO_5_triangles = 0;
glGenBuffers(1, &VBO_5_triangles);
glBindBuffer(GL_ARRAY_BUFFER, VBO_5_triangles);
glBufferData(GL_ARRAY_BUFFER, sizeof(points_5_triangles), points_5_triangles, GL_STATIC_DRAW);
// Generate another VAO.
GLuint VAO_5_triangles = 0;
glGenVertexArrays(1, &VAO_5_triangles);
glBindVertexArray(VAO_5_triangles);
glBindBuffer(GL_ARRAY_BUFFER, VBO_5_triangles);
glBufferData(GL_ARRAY_BUFFER, sizeof(points_5_triangles), points_5_triangles, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
glEnableVertexAttribArray(0);
现在绘制两个对象时，您将首先绑定目标VAO，然后进行渲染，然后继续执行下一个对象：
glBindVertexArray(VAO); glDrawArrays(GL_TRIANGLES, 0, 3); glBindVertexArray(VAO_5_triangles); glDrawArrays(GL_TRIANGLE_FAN, 0, 7);
有关如何绘制三角形风扇的更多信息，请参见https://www.khronos.org/opengl/wiki/Primitive#Triangle_primitives
aColor）指定输入属性，并将颜色属性从顶点着色器传递到片段着色器（myColor）。用Layout Qualifiers指定属性索引。 #version 330 core
layout(location = 0) in vec3 aPos;
layout(location = 1) in vec3 aColor;
out vec3 myColor;
void main()
{
myColor = aColor;
gl_Position = vec4(aPos, 1.0);
}
#version 330 core
out vec4 FragColor;
in vec3 myColor;
void main()
{
FragColor = vec4(myColor, 1.0f);
}
请注意，您当前的顶点着色器无法编译。通过glGetShaderiv和参数glGetShaderiv检查是否成功完成了着色器的编译，并且可以通过GL_COMPILE_STATUS和参数glGetProgramiv检查程序的链接是否成功。有关某些代码段，请参见glGetProgramiv的答案。
您的顶点是具有6个成分（x，y，z，r，g，b）的元组：GL_LINK_STATUS
使用OpenGL ignores Quads and makes them Triangles指定2个顶点属性。步幅和偏移量必须以字节为单位指定。跨度为float points[] = { // positions // colors 0.0f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 0.5f, -0.5f, 0.0f, 0.0f, 1.0f, 0.0f, -0.5f, -0.5f, 0.0f, 0.0f 0.0f, 1.0f };。顶点坐标的偏移为0，颜色属性的偏移为glVertexAttribPointer。例如：
glVertexAttribPointer
如果要绘制更复杂的网格，则必须扩展vertes数组。只需在6 * sizeof(float)数组中为下一个三角形添加另外3个顶点和颜色即可。或者，您可以使用其他原始类型，例如3 * sizeof(float)或GLuint VBO = 0; glGenBuffers(1, &VBO); glBindBuffer(GL_ARRAY_BUFFER, VBO); glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW); // Generate a VAO. GLuint VAO = 0; glGenVertexArrays(1, &VAO); glBindVertexArray(VAO); glEnableVertexAttribArray(0); glEnableVertexAttribArray(1); glBindBuffer(GL_ARRAY_BUFFER, VBO); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), NULL); glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)(3 * sizeof(float)));。参见points