一个不渲染的简单顶点缓冲对象(C )

Question

im试图使用VBO将正常的2D纹理正方形渲染到FBO上。即时模式功能可完美地工作，但该VBO效果不佳。GL_TEXTURE_2D已启用了代码。怎么了？

unsigned int VBOid = 0;
unsigned int Iid = 0;
float *geometry;
unsigned int *indices;
int num_geometry = 1;
int num_vertices = 4;
int num_indices = num_geometry*num_vertices;
geometry = new float[num_geometry*num_vertices*4];
indices = new unsigned int[num_indices];
indices[0] = 0;
indices[1] = 1;
indices[2] = 2;
indices[3] = 3;
/* Fill geometry: 0, 1, = vertex_xy
*                2, 3 = tex_coord_uv
*/
geometry[0] = 0.0f;
geometry[1] = 0.0f;
geometry[2] = 0.0f;
geometry[3] = 0.0f;
geometry[4] = 50.0f;
geometry[5] = 0.0f;
geometry[6] = 1.0f;
geometry[7] = 0.0f;
geometry[8] = 50.0f;
geometry[9] = 50.0f;
geometry[10] = 1.0f;
geometry[11] = 1.0f;
geometry[12] = 0.0f;
geometry[13] = 50.0f;
geometry[14] = 0.0f;
geometry[15] = 1.0f;
glGenBuffers(1, &VBOid);
glBindBuffer(GL_ARRAY_BUFFER, VBOid);
glBufferData(GL_ARRAY_BUFFER, sizeof(geometry), geometry, GL_STATIC_DRAW);
glGenBuffers(1, &Iid);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, Iid);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
//GL_TEXTURE_2D is already enabled here
//Buffers are already bound from above
glBindTexture( GL_TEXTURE_2D, 2); //I used 2 just to test to see if it is rendering a texture correctly. Yes, 2 does exist in my program thats why i arbitrarily used it
//glClientActiveTexture(GL_TEXTURE0); I dont know what this is for and where to put it
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
//glActiveTexture(GL_TEXTURE0); same here I dont know what this is for or where to put it
glVertexPointer(2, GL_FLOAT, sizeof(GLfloat)*4, 0);
glTexCoordPointer(2, GL_FLOAT, sizeof(GLfloat)*4, (float*)(sizeof(GLfloat)*2));
glDrawElements(GL_QUADS, num_indices, GL_UNSIGNED_INT, indices);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

Answer 1

问题是您在glBufferData调用中使用sizeof(geometry)（以及indices）的使用情况。这些变量实际上只是指针，无论它们是否指向动态分配的数组（编译器不知道）。因此，您将始终获得指针的大小（4或8个字节，具体取决于平台）。

用num_geometry*num_vertices*4*sizeof(float)替换sizeof(geometry)，用num_indices*sizeof(unsigned int)替换CC_7。好吧，实际上，您根本不需要任何索引，只能用简单的

绘制整个内容

glDrawArrays(GL_QUADS, 0, 4);

始终意识到实际（编译时大小）数组和仅指向动态分配的数组的指针之间的差异，而sizeof操作员是这些差异的一个的结果（以及在以后的某个时间点上使用delete[]释放后者的内存的要求，但差异也不重要）。