Runs only once
GLfloat vertices[] = {
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
0.5f, 0.5f, 0.0f,
-0.5f, 0.5f, 0.0f
};
GLuint triangles[] = {0,1,2};
int lengthV = 3; //Number of vertices
int lenfthT = 1; //Number of triangles
glGenVertexArrays(1, &vaoID);
glBindVertexArray(vaoID);
glGenBuffers(vaoID, &verticesVBOID);
glBindBuffer(GL_ARRAY_BUFFER, verticesVBOID);
glBufferData(GL_ARRAY_BUFFER, lengthV*sizeof(GLfloat)*3, vertices, GL_STATIC_DRAW);
glGenBuffers(vaoID, &trianglesVBOID);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, trianglesVBOID);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, lengthT*sizeof(GLuint)*3, triangles, GL_STATIC_DRAW);
Runs once per frame
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, verticesVBOID);
glVertexAttribPointer(0, lengthV, GL_FLOAT, GL_FALSE, 0, nullptr);
glUseProgram(program);
//glDrawArrays(GL_TRIANGLES, 0, verticeCount*3);
glDrawElements(GL_TRIANGLES, lengthT,GL_UNSIGNED_INT, nullptr);
glDisableVertexAttribArray(0);
glfwSwapBuffers(window);
When I run this, this renders, which is right.
When I change the number of vertices to 4 to try and render a quad eventually.
int lengthV = 4;
This happens.
I don't understand why this is happening because I only changed the number of vertices.
Ive Tried to find an answer but I could not. I have looked at this persons problem and his code looks the same as mine after applying the answer. No display from glDrawElements
You missinterpret the second parameter of glVertexAttribPointer
.
The size parameter specifies the number of components of an attribute (which basically is the number of floats it gets). Since you still have a vec3 (3 floats) per vertex when drawing a quad, this number shouldn't be changed.
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