[英]Why can I have an OpenGL shader class, but not a VAO class?
我一直在摆弄一个游戏/渲染引擎,我发现我可以有一个着色器对象的类,但是如果我将一个 VAO 包装在一个类中,它就不会渲染。
着色器不会返回任何错误,并且 VAO 和着色器是有效的 OpenGL 对象。
更新
问题是这一行:
glBufferData(GL_ARRAY_BUFFER, sizeof(arrFVertex), arrFVertex, GL_STATIC_DRAW);
正如@BDL 在评论中所建议的那样,我考虑了一下,意识到应该是:
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * intNumVertex * 3, arrFVertex, GL_STATIC_DRAW);
更新 2作为对被搁置的回应,这是一个最小完整和可验证的示例:
#include <OpenGL/gl3.h>
#include <SDL2/SDL.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
SDL_Window *window = NULL;
SDL_GLContext openGLRenderer;
bool bolRunning = true;
int intGLVersionMajor, intGLVersionMinor;
GLfloat arrFVertex[] = {
0.5f, 0.5f, 0.0f, // Top Right
0.5f, -0.5f, 0.0f, // Bottom Right
-0.5f, 0.5f, 0.0f, // Top Left
0.5f, -0.5f, 0.0f, // Bottom Right
-0.5f, -0.5f, 0.0f, // Bottom Left
-0.5f, 0.5f, 0.0f // Top Left
};
GLuint intVAO;
GLuint intVBO;
GLuint intShaderAttribPosition;
GLuint intShaderProgram;
GLuint intNumVertex = 6;
void loadShaders(const char *strVertexShaderSource, const char *strFragmentShaderSource) {
intShaderProgram = glCreateProgram();
GLuint intVertexShader;
intVertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(intVertexShader, 1, &strVertexShaderSource, NULL);
glCompileShader(intVertexShader);
GLuint intFragmentShader;
intFragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(intFragmentShader, 1, &strFragmentShaderSource, NULL);
glCompileShader(intFragmentShader);
glAttachShader(intShaderProgram, intVertexShader);
glAttachShader(intShaderProgram, intFragmentShader);
glLinkProgram(intShaderProgram);
glDeleteShader(intVertexShader);
glDeleteShader(intFragmentShader);
}
void buildVAO(GLfloat *arrFVertex) {
intShaderAttribPosition = glGetAttribLocation(intShaderProgram, "f3Position");
glGenVertexArrays(1, &intVAO);
glBindVertexArray(intVAO);
glGenBuffers(1, &intVBO);
glBindBuffer(GL_ARRAY_BUFFER, intVBO);
glVertexAttribPointer(intShaderAttribPosition, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid *)0);
glEnableVertexAttribArray(intShaderAttribPosition);
glBufferData(GL_ARRAY_BUFFER, sizeof(arrFVertex), arrFVertex, GL_STATIC_DRAW);
glBindVertexArray(0);
}
int main(int argc, char **argv) {
SDL_Init(SDL_INIT_EVERYTHING);
window = SDL_CreateWindow("GSEngine",
SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
640, 480,
SDL_WINDOW_OPENGL);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
if (window == NULL) {
printf("Could not create window: %s\n", SDL_GetError());
exit(1);
}
openGLRenderer = SDL_GL_CreateContext(window);
SDL_GL_MakeCurrent(window, openGLRenderer);
glViewport(0, 0, 640, 480);
loadShaders("#version 330 core\n\
in vec3 f3Position;\n\
void main() {\n\
gl_Position = vec4(f3Position, 1.0);\n\
}", "#version 330 core\n\
out vec4 f4Color;\n\
void main() {\n\
f4Color = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n\
}");
buildVAO(arrFVertex);
while (bolRunning) {
SDL_Event event;
while (SDL_PollEvent(&event)) {
if (event.type == SDL_QUIT) {
bolRunning = false;
}
}
SDL_GL_MakeCurrent(window, openGLRenderer);
glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(intShaderProgram);
glDrawArrays(GL_TRIANGLES, 0, intNumVertex);
SDL_GL_SwapWindow(window);
}
glDeleteBuffers(1, &intVBO);
glDeleteVertexArrays(1, &intVAO);
glDeleteShader(intShaderProgram);
SDL_GL_DeleteContext(openGLRenderer);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}
问题与VAO无关,而是与VBO有关。 由于您将指针传递给构造函数:
void GSMesh::build(GLfloat *arrFVertex, GSShader *shader, int _intNumVertex)
{
glBufferData(GL_ARRAY_BUFFER, sizeof(arrFVertex), arrFVertex, GL_STATIC_DRAW);
}
sizeof(arrFVertex)
= sizeof(GLfloat*)
这是指针的大小,而不是指向的数组的大小。 正确的代码如下所示:
glBufferData(GL_ARRAY_BUFFER,
sizeof(GLfloat) * _intNumVertex * 3, arrFVertex,
GL_STATIC_DRAW);
总的来说,我必须补充一点,这不是在 SO 上提问的方式。 如果您至少在问题中包含代码的相关部分,那就太好了。
不管规范怎么说,对于某些驱动程序,您必须先启用着色器,然后才能获取属性或制服的位置。 这可能是导致您出现问题的原因。
在您的代码中,这意味着在您的 GSMesh::build 方法中添加:
shader->use();
前:
intShaderAttribPosition = glGetAttribLocation(shader->intShaderProgram, "f3Position");
就个人而言,如果您使用的 OpenGL 版本支持顶点属性索引,我会改用它们。
在顶点着色器中,你可以有这样的东西:
layout (location = 0) in vec3 position;
layout (location = 1) in vec2 tex_coords;
然后在您的网格类中,您只需要:
struct Vertex
{
glm::vec3 position;
glm::vec2 tex_coords;
};
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*)offsetof(Vertex, position);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*)offsetof(Vertex, tex_coords));
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