On my journey towards being competent at OpenGL, I was trying to make a textured cube when I came upon this problem: Only part of my cube is being rendered. There should be 12 triangles but only 3 of them are being rendered. I've looked at many tutorials, but I can't seem to find the problem/main difference between our code. Here's mine:
...
int main(int argc, char* argv[]) {
if (!setupGLFW()) return 1;
setupApple();
glfwWindowHint(GLFW_SAMPLES, 4);
GLFWwindow* window = glfwCreateWindow(WIN_WIDTH, WIN_HEIGHT, "Textured Cube", NULL, NULL);
if (!window) {
log_msg(LOG_ERROR, "Could not open a GLFW3 window!\n");
return 1;
}
glfwMakeContextCurrent(window);
if (!setupGLEW()) return 1;
glClearColor(0.5, 0.5, 0.5, 1.0);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
static const int vertices = 12 * 3;
static const GLfloat points[] = {
-1.0, -1.0, -1.0,
-1.0, -1.0, 1.0,
-1.0, 1.0, 1.0,
1.0, 1.0, -1.0,
-1.0, -1.0, -1.0,
-1.0, 1.0, -1.0,
1.0, -1.0, 1.0,
-1.0, -1.0, -1.0,
1.0, -1.0, -1.0,
1.0, 1.0, -1.0,
1.0, -1.0, -1.0,
-1.0, -1.0, -1.0,
-1.0, -1.0, -1.0,
-1.0, 1.0, 1.0,
-1.0, 1.0, -1.0,
1.0, -1.0, 1.0,
-1.0, -1.0, 1.0,
-1.0, -1.0, -1.0,
-1.0, 1.0, 1.0,
-1.0, -1.0, 1.0,
1.0, -1.0, 1.0,
1.0, 1.0, 1.0,
1.0, -1.0, -1.0,
1.0, 1.0, -1.0,
1.0, -1.0, -1.0,
1.0, 1.0, 1.0,
1.0, -1.0, 1.0,
1.0, 1.0, 1.0,
1.0, 1.0, -1.0,
-1.0, 1.0, -1.0,
1.0, 1.0, 1.0,
-1.0, 1.0, -1.0,
-1.0, 1.0, 1.0,
1.0, 1.0, 1.0,
-1.0, 1.0, 1.0,
1.0, -1.0, 1.0
};
static const GLfloat textureCoords[] = {
0, 0,
1, 0,
0, 1,
0, 1,
1, 0,
1, 1,
0, 0,
1, 0,
0, 1,
0, 1,
1, 0,
1, 1,
0, 0,
1, 0,
0, 1,
0, 1,
1, 0,
1, 1,
0, 0,
1, 0,
0, 1,
0, 1,
1, 0,
1, 1,
0, 0,
1, 0,
0, 1,
0, 1,
1, 0,
1, 1,
0, 0,
1, 0,
0, 1,
0, 1,
1, 0,
1, 1,
};
GLuint pointBuffer;
glGenBuffers(1, &pointBuffer);
glBindBuffer(GL_ARRAY_BUFFER, pointBuffer);
glBufferData(GL_ARRAY_BUFFER, vertices * 3, points, GL_STATIC_DRAW);
GLuint textureBuffer;
glGenBuffers(1, &textureBuffer);
glBindBuffer(GL_ARRAY_BUFFER, textureBuffer);
glBufferData(GL_ARRAY_BUFFER, vertices * 2, textureCoords, GL_STATIC_DRAW);
GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
glBindBuffer(GL_ARRAY_BUFFER, pointBuffer);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
glBindBuffer(GL_ARRAY_BUFFER, textureBuffer);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, NULL);
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
GLuint program = getProgramFromFiles("text_cube.vs.glsl", "text_cube.fs.glsl");
glm::mat4 MVP = calculateMVP();
GLuint texture = loadBMP("uvtemplate.bmp");
if (!program) {
log_msg(LOG_ERROR, "There was a problem opening shader.\n");
// clean up
return 1;
}
if (!texture) {
log_msg(LOG_ERROR, "There was a problem opening shader.\n");
// clean up
return 1;
}
glUseProgram(program);
GLuint MVPID = glGetUniformLocation(program, "MVP");
GLuint textureID = glGetUniformLocation(program, "cube_texture");
glUniformMatrix4fv(MVPID, 1, GL_FALSE, &MVP[0][0]);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture);
glUniform1i(textureID, 0);
while (!glfwWindowShouldClose(window) && glfwGetKey(window, GLFW_KEY_ESCAPE) != GLFW_PRESS) {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glDrawArrays(GL_TRIANGLES, 0, vertices);
glfwPollEvents();
glfwSwapBuffers(window);
}
// clean up
return 0;
}
Just so you know, the error is not with setupGLFW()
, setupApple()
, setupGLEW()
, getProgramFromFiles()
, calculateMVP()
, loadBMP()
, or my vertex and fragment shaders, which are in different files. This compiles fine because I include GLFW
and GLEW
from myglutils.h
This is uvtemplate.bmp
, its a 512x512 image:
If you guys could help me, it would be greatly appreciated. Thanks!
The problem is the call to glBufferData()
. You set the size in floats but you have to specify it in bytes using sizeof(GLfloat)
. That's why OpenGL isn't receiving all of your data.
void glBufferData
(
GLenum target,
GLsizeiptr size,
const GLvoid* data,
GLenum usage
);
So you need to replace:
glBufferData(GL_ARRAY_BUFFER, vertices * 3, points, GL_STATIC_DRAW);
glBufferData(GL_ARRAY_BUFFER, vertices * 2, textureCoords, GL_STATIC_DRAW);
with:
glBufferData(GL_ARRAY_BUFFER, vertices * 3 * sizeof(GLfloat), points, GL_STATIC_DRAW);
glBufferData(GL_ARRAY_BUFFER, vertices * 2 * sizeof(GLfloat), textureCoords, GL_STATIC_DRAW);